Copolyéthersulfones rigides-flexibles : Modulation des propriétés … · 2018-04-25 · vi 2.2.3.4 Synthesis of 4-fluoro-4-hydroxy diphenyl sulfone (FHDS) (Scheme 2.1b) . 442.2.3.5

Copolyéthersulfones rigides-flexibles : Modulation

des propriétés par modification du segment flexible

Thèse

Adrien Faye

Doctorat de chimie

Philosophiae doctor (Ph.D.)

Québec, Canada

© Adrien Faye, 2016

Copolyéthersulfones rigides-flexibles : Modulation

des propriétés par modification du segment flexible

Thèse

Adrien Faye

Sous la direction de :

Josée Brisson, directrice de recherche

iii

Résumé

La présente thèse traite trois thèmes principaux. Le premier volet concerne le contrôle

de la cristallinité et la synthèse des polyéthersulfones avec incorporation de doubles

liaisons comme espaceurs dans les chaînes du polymère en utilisant deux approches

différentes : la polymérisation par métathèse des diènes acycliques (ADMET) et la

polycondensation. L’ADMET a permis d’obtenir des copolymères de faibles

polydispersités avec des doubles liaisons régulièrement réparties le long des chaînes

du polymère. La polycondensation a permis d’obtenir des copolymères de

configuration cis ou trans avec incorporation régulière ou aléatoire des doubles

liaisons. Pour la synthèse par ADMET, un bloc rigide, terminé par des groupements

allyliques, est polymérisé dans le dichlorométhane à l’aide de l’un des catalyseurs de

Grubbs : Grubbs deuxième génération (G2) ou Hoveyda-Grubbs (HG). Concernant la

polycondensation, on fait réagir un bloc rigide avec un segment flexible de

configuration cis ou trans pour obtenir respectivement le copolymère cis ou trans. La

diffraction des rayons X et l’analyse enthalpique différentielle (DSC) ont montré que

l’isomère cis inhibe complètement la cristallinité alors que la forme trans la favorise.

Le deuxième volet de ce travail repose principalement sur la polycondensation en un

seul pot « one pot en anglais» qui a permis de contrôler les températures de transition

vitreuse. La spectrométrie de masse MALDI-TOF a permis de démontrer que les

copolymères obtenus avec variation du ratio bloc rigide/segment flexible sont de

nature aléatoire et non des copolymères blocs.

Le troisième et dernier thème de ce document concerne principalement le contrôle de

l’hydrophilicité par une post-fonctionnalisation des copolymères à travers les doubles

liaisons incorporées en utilisant les réactions thiol-ène clic. Le but étant de moduler

les propriétés des copolymères pour les adapter à des applications bien définies. Pour

une application dans la filtration membranaire par exemple, des chaînes hydrophiles

ont été greffées à travers ces doubles liaisons pour augmenter l’hydrophilicité des

copolymères.

iv

Abstract

This thesis deals with three main themes. The first component relates to the control of

the crystallinity and the synthesis of polyethersulfones with incorporation of double

bonds as a spacer in the polymer chains using two different approaches: ADMET

(Acyclic Diene Metathesis Polymerization) and polycondensation reactions. ADMET

leads to copolymers with low polydispersity index and double bonds regularly

distributed along the polymer chains. Polycondensation allows obtaining directly cis

or trans configuration copolymers with regular or random incorporation of the double

bonds. For the synthesis by ADMET, a rigid block terminated by allyl groups is

dissolved in dichloromethane and then polymerized using second generation Grubbs

catalyst (G2) and Hoveyda-Grubbs catalyst (HG). Concerning the polycondensation

reaction, a rigid block reacts with a flexible segment of cis or trans configuration to

respectively give the cis or trans copolymer. X-ray diffraction and differential

scanning calorimetry (DSC) showed that the cis isomer inhibits crystallization while

the trans form favors it.

The second part of this work is mainly based on the one-pot polycondensation

reaction which allowed control the glass transition. MALDI-TOF mass spectrometry

was used to show that copolymers obtained by the variation of the rigid bloc/flexible

segment ratio are random and not block copolymers.

The third subject of this document mainly concerns the control of the hydrophilicity

by post-functionalization of copolymers through the double bonds incorporated using

thiol-ene click reactions. The main goal is to modulate the properties of copolymers

to suit well-defined applications. For example, for applications in membrane

filtration, hydrophilic chains were grafted through double bonds to increase the

copolymer hydrophilicity.

v

Table des matières

Résumé ........................................................................................................................ iii Abstract ....................................................................................................................... iv

Table des matières ........................................................................................................ v Liste des tableaux ........................................................................................................ ix Liste des schémas ......................................................................................................... x Liste des figures .......................................................................................................... xi Abréviations .............................................................................................................. xiv

Symboles .................................................................................................................. xvii Dédicaces ................................................................................................................ xviii

Remerciements ........................................................................................................... xx

Avant-propos ............................................................................................................ xxii

Chapitre 1 : Introduction générale ............................................................................... 1 1.1 Revue de la littérature sur la synthèse des PES...................................................... 2

1.2 Les réactions thiol-ène clic radicalaires ................................................................. 5 1.3 Domaine d’application des PES ............................................................................. 7

1.3.1 Filtration membranaire ...................................................................................... 10 1.4 Problématique ...................................................................................................... 11 I.5 Objectif du projet .................................................................................................. 15

1.6 Méthodologie ....................................................................................................... 17 1.6.1 Polymérisation par métathèse des diènes acycliques (ADMET) ...................... 17

1.6.2 Polycondensation .............................................................................................. 21

1.6.3 Caractérisation des polymères ......................................................................... 22

1.6.4 Post-fonctionnalisation des copolymères ......................................................... 27 1.6.5 Mesures d’angle de contact ............................................................................... 27

1.7 Références ............................................................................................................ 30

Chapitre 2: Crystallization control of etherethersulfone copolymers by regular

insertion of an allyl functionality ............................................................................... 34 Résumé ....................................................................................................................... 35 Abstract ...................................................................................................................... 36

2.1 Introduction .......................................................................................................... 37 2.2 Experimental section ............................................................................................ 39 2.2.1 Instrumentation ................................................................................................. 39

2.2.2 Materials ............................................................................................................ 40 2.2.3 Synthesis of monomers ..................................................................................... 41 2.2.3.1 Synthesis of 4,4’-bis(4-methoxyphenoxy) diphenyl sulfone (MPDS)

(Scheme 2.1a) ............................................................................................................. 41

2.2.3.2 Synthesis of 4,4’-Bis(4-hydroxyphenoxy) diphenyl sulfone (HPDS) (Scheme

2.1a) ........................................................................................................................... 42 2.2.3.3 Synthesis of 4,4’-bis(4-allyloxyphenoxy) diphenyl sulfone (APDS) (Scheme

2.1a) ........................................................................................................................... 43

vi

2.2.3.4 Synthesis of 4-fluoro-4’-hydroxy diphenyl sulfone (FHDS) (Scheme 2.1b) . 44

2.2.3.5 Synthesis of 4-fluoro-4’-methoxy diphenyl sulfone (FMDS) (Scheme 2.1b) 44

2.2.3.6 Synthesis of 4,4’-bis(4-(4-(4-methoxyphenylsulfonyl)

phenoxy)pentoxy)diphenylsulfone (MPSPPDS) (Scheme 2.1b)................................ 45 2.2.3.7 Synthesis of 4,4’-bis(4-(4-(4-hydroxyphenylsulfonyl)phenoxy)phenoxy)

diphenyl sulfone (HPSPPDS) (Scheme 2.1b)............................................................. 46 2.2.4 Copolymer synthesis ......................................................................................... 46

2.2.4.1 ADMET polymerization of poly(allyl-co-etherethersulfone) (PA-4EES)

(Scheme 2.2a) ............................................................................................................. 46 2.2.4.2 Polycondensation of PTA-4EES, PTCA-4EES, PTA-8EES and PCA-8EES

copolymers (Schemes 2.2b and 2.2c) ......................................................................... 47 2.2.4.3 Polycondensation of the PAE-4EES copolymer (Scheme 2.2d) .................... 47

2.2.4.4 Hydrogenation to obtain PAH-4EES and PAH-8EES ................................... 47

2.2.4.5 Halogenation to obtain PACl-4EES and PABr-4EES ................................... 48 2.2.5 Recrystallization of copolymers. ....................................................................... 48

2.2.6 Results and discussion ...................................................................................... 49

2.2.6.1 Synthesis of polymers .................................................................................... 49 2.2.6.1.1 PA-4EES copolymer obtained by ADMET polymerization ....................... 50

2.2.6.1.2 PTA-xEES and PCA-xEES polymers obtained by polycondensation ........ 52 2.2.7 Post-polymerization reactions ........................................................................... 55 2.2.8 Thermal properties of the copolymers .............................................................. 57

2.2.8.1 Thermogravimetric analysis (TGA) ............................................................... 57 2.2.8.2 Differential scanning calorimetry (DSC) ....................................................... 58

2.2.9 X-ray diffraction................................................................................................ 62 2.2.10 Double melting behaviour ............................................................................... 68

2.3 Conclusion ........................................................................................................... 70 2.4 Acknowledgements .............................................................................................. 71

2.5 References ............................................................................................................ 72

Chapitre 3: Synthesis of High Molecular Weight Polyetherethersulfone - Allyl

Copolymers of Controlled glass transition ................................................................ 74 Résumé ....................................................................................................................... 75

Abstract ...................................................................................................................... 76 3.1 Introduction .......................................................................................................... 77 3.2 Experimental section ............................................................................................ 78 3.2.1 Instrumentation ................................................................................................. 78 3.2.2 Materials ............................................................................................................ 80

3.2.3 Synthesis of the monomer: 4,4’-bis(4-hydroxyphenoxy) diphenyl sulfone

(HPDS) ....................................................................................................................... 80

3.2.4 Polymers synthesis ............................................................................................ 80 3.2.4.1 PEES synthesis10 ............................................................................................ 80 3.2.4.2 Synthesis of poly(4EES-alt-cb) and poly(4EES-alt-tb) ................................. 81 3.2.4.3 Synthesis of poly(6EES-ran-4EEScb) ........................................................... 83 3.2.5 Copolymer film preparation .............................................................................. 83

3.2.6 Chemical aging studies ..................................................................................... 83

vii

3.3 Results and discussion ......................................................................................... 84

3.3.1 Optimization of the synthesis of poly(4EES-alt-cb) and poly(4EES-alt-tb) ..... 84

3.3.2 One-pot synthesis of copolymers with longer rigid segments, poly(6EES-ran-

4EEScb)...................................................................................................................... 86 3.3.3 MALDI-TOF investigation of the copolymers ................................................. 88 3.3.4 Thermal properties of copolymers .................................................................. 100 3.3.4.1 Thermogravimetric analyses ........................................................................ 100

3.3.4.2 DSC measurements ...................................................................................... 101 3.3.5 Chemical aging studies ................................................................................... 104 3.4 Conclusion ......................................................................................................... 107 3.5 Acknowledgements ............................................................................................ 107 3.6 References .......................................................................................................... 108

Chapitre 4: Postfunctionalization by thiol-ene click reactions of

polyetherethersulfone-allyl copolymers for applications in membrane filtration ... 109

Résumé ..................................................................................................................... 110

Abstract .................................................................................................................... 111 4.1 Introduction ........................................................................................................ 112

4.2 Experimental section .......................................................................................... 114 4.2.1 Instrumentation ............................................................................................... 114 4.2.2 Materials .......................................................................................................... 115

4.2.3 Synthesis of S-2-(2-(2-hydroxyethoxy)ethoxy)ethyl thioacetate (scheme

4.1)20 ......................................................................................................................... 116

4.2.4 Synthesis of 2-(2-(2-hydroxyethoxy)ethoxy)ethanethiol (PEG2-thiol) (scheme

4.1)21 ......................................................................................................................... 116

4.2.5 Synthesis of the monomer: 4,4’-bis(4-hydroxyphenoxy) diphenyl sulfone

(HPDS) ..................................................................................................................... 117

4.2.6 Polymers and copolymers used in this work ................................................... 117 4.2.7 Post-functionalization of copolymers by thiol-ene click reactions19 .............. 118 4.2.8 Solubility test of the cross-linked copolymer ................................................. 122

4.2.9 CHNS Elementary Analysis ............................................................................ 122 4.2.9.1 Cross-linking with 2,2′-(ethylenedioxy) diethanethiol (PEG2-dithiol) ........ 123

4.2.9.1.1 Theoretical percentage calculation of carbon atoms contained in the

copolymer after cross-linking (poly(4EES-alt-cb)-crosslink-PEG2), considering one

chain grafted per double bond .................................................................................. 123 4.2.9.1.2 Theoretical percentage calculation of carbon atoms contained in the

copolymer after cross-linking (poly(4EES-alt-cb)-crosslink-PEG2) considering two

chains grafted per double bond ................................................................................ 124 4.2.9.2 Cross-linking with 1,3-propanedithiol (Pr-dithiol) ...................................... 124


copolymer after cross-linking (poly(4EES-alt-cb)-crosslink-Pr) ............................. 124 4.2.10 Cross-link density measurements .................................................................. 125 4.2.11 Copolymer film preparation .......................................................................... 127 4.2.12 Cross-linked copolymer film preparation ..................................................... 127

4.3 Results and discussion ....................................................................................... 127

viii

4.3.1 PES and PEES ................................................................................................. 127

4.3.2 Alternate and random copolymer synthesis .................................................... 128

4.3.3 Post-functionalization of copolymers by thiol-ene click reactions ................. 128 4.3.4 Hydrophilicity and hydrophobicity studies ..................................................... 135 4.3.5 Film cross-linking ........................................................................................... 137 4.4 Conclusion ......................................................................................................... 140 4.5 Acknowledgements ............................................................................................ 141

4.6 References .......................................................................................................... 142

Chapitre 5 : Conclusion et Recommandations ......................................................... 144 5.1 Références .......................................................................................................... 149 Annexes .................................................................................................................... 150

Bibliographie générale ............................................................................................. 176

ix

Liste des tableaux

Tableau 1.1 : Famille des polyéthersulfones avec leurs abréviations, structures

chimiques, noms commerciaux, producteurs et années de synthèse1 .......................... 2

Tableau 1.2: Réactivité des catalyseurs à base de titane, tungstène, molybdène et

ruthénium vis-à-vis des oléfines en présence de groupements fonctionnels

hétéroatomiques62 ....................................................................................................... 18

Table 2.1: Molecular weights and dispersity of polymers synthesized by ADMET

and polycondensationa ............................................................................................... 56

Table 2.2: Proton chemical shifts (d) of the allyl group in cis- and trans

poly(etherethersulfones) obtained by polycondensation and by ADMET (major

configuration trans) .................................................................................................... 57

Table 3.1: Monomer ratios used in the synthesis of poly(6EES-ran-4EEScb) ......... 83

Table 3.2: Number molecular weight (Mn), degree of polymerization (DP) and

polydispersity index (Ip) of Poly(4EES-alt-tb), Poly(4EES-alt-cb) and PEES ......... 85

Table 3.3: DSC and SEC data of copolymers synthesized with varying

6EES/4EEScb ratios ................................................................................................... 87

Table 3.4: Proposed assignment for the main MALDI-TOF fragments of the PEES

homopolymer ............................................................................................................. 91

Table 3.5: Proposed assignment for the main MALDI-TOF fragments for the

poly(4EES-alt-cb) in the 1000 - 5000 g mol−1 range (only the most intense peaks are

reported in this Table) ................................................................................................ 92


poly(6EES-ran-4EEScb) in the 1000 - 3500 g.mol−1 range (only the most intense

peaks are reported in this Table) ................................................................................ 93

Table 3.7: Proposed assignment for additional MALDI-TOF fragments for the

poly(4EES-alt-cb) and poly(6EES-ran-4EEScb) in the 1000 - 4000 g mol−1 range .. 97

Table 3.8: Number molecular weight (Mn) and polydispersity index (Ip) of

poly(4EES-alt-cb) and poly(6EES-ran-4EEScb) copolymers before and after

immersed in bleach .................................................................................................. 105

Table 4.1: Grafted and cross-linked molecules and their abbreviations ................. 119

Table 4.2: Number molecular weights (Mn), degree of polymerization (DP) and

polydispersity index (Ip) of synthesized polyethersulfone (PES) and

polyetherethersulfone (PEES) .................................................................................. 127

Table 4.3: Number molecular weight, polydispersity index, glass transition

temperature and contact angles of copolymers and functionalized copolymers ...... 129

Table 4.4: Carbon elementary analysis and solubility of copolymers cross-linked

with PEG2-dithiol and Pr-dithiol. ............................................................................ 135

Table 4.5: Glass transition temperatures and contact angles of Poly(6EES-ran-

4EEScb) before and after surface cross-linking ....................................................... 138

Table A.2.1: Comparison of diffraction peak position for PES and polymers

synthesized in the present work ............................................................................... 150

x

Liste des schémas

Schéma 1.1 : Formule chimique du PES ..................................................................... 1 Schéma 1.2 : Synthèse des PES par polysulfonylation utilisée par 3M Corporation12 3

Schéma 1.3 : Synthèse des PES par polyétherification utilisée par Union Carbide

Corporation et ICI12...................................................................................................... 4 Schéma 1.4 : Synthèse des PEES par polyétherification utilisée par Plastics division

of ICI12 ......................................................................................................................... 4 Schéma 1.5 : Mécanisme de substitution nucléophile aromatique .............................. 5

Schéma 1.6 : Mécanisme radicalaire du DMPA26 ....................................................... 7 Schéma 1.7 : Mécanisme de la réaction thiol-ène clic18,25,27 ....................................... 7

Schéma 1.8 : Catalyseurs de Grubbs utilisés pour l’ADMET................................... 19

Schéma 1.9: Polymérisation par métathèse des diènes acycliques (ADMET) .......... 20 Schéma 1.10 : Mécanisme de polymérisation par métathèse des diènes acycliques

(ADMET)69,70 ............................................................................................................. 21 Schéma 1.11: Illustration de la polycondensation entre un bloc rigide et un segment

flexible........................................................................................................................ 22 Schéma 1.12: Principe de fonctionnement d’un spectromètre de masse MALDI-

TOF.72 ........................................................................................................................ 25 Scheme 2.1: Synthesis of monomer precursors: (a) APDS (4-ring) precursor and (b)

HPSPPDS (8-ring) precursor ..................................................................................... 42

Scheme 2.2: Polymerization reactions: (a) acyclic diene metathesis polymerization

(ADMET) of the APDS monomer, (b) polycondensation of HPDS with (Z) and (E)-

1,4-dichlorobut-2-ene, (c) polycondensation of HPSPPDS with (Z) and (E)-1,4-

dichlorobut-2-ene and (d) polycondensation with fumaryl chloride to insert ester

linkages. ..................................................................................................................... 49 Scheme 3.1: Synthesis of random and alternate copolymers: a) Poly(4EES-alt-cb)

and poly(4EES-alt-tb) alternate copolymers and b) Poly(6EES-ran-4EEScb) random

copolymer (one pot polycondensation reaction) ........................................................ 82 Scheme 3.2: Repeat units and molar masses of various copolymers reported in the

MALDI-TOF study .................................................................................................... 94 Scheme 4.1: Synthesis of 2-(2-(2-hydroxyethoxy)ethoxy)ethanethiol (PEG2-thiol)116 Scheme 4.2 : Polymers and copolymers used in this work...................................... 117

Scheme 4.3: Thiol-ene click reactions onto poly(4EES-alt-cb) copolymer : a) PEG2-

thiol chain grafting and b) Pr-dithiol and PEG2-dithiol chains cross-linking .......... 120 Schéma 5.1 : Illustration de la possibilité d’une liaison intramoléculaire entre

l’oxygène proche de la double liaison et le métal central du catalyseur2................. 145 Schéma A.2.1: Mn calculation by NMR .................................................................. 167

xi

Liste des figures

Figure 1.1 : Filtration du lait caillé pour la production du fromage ............................... 9

Figure 1.2 : Principe d’une membrane de filtration selon Prulho41 ............................. 10

Figure 1.3 : Images MEB en coupe plane (a) et transversale (b) d’une membrane

colmatée (agrégat de particules encerclé en vert) 50 ...................................................... 14

Figure 1.4 : Images MEB d’une coupe transversale d’une membrane de PES seul (a)

et d’un mélange PES/PAN dans un rapport massique 70/30 (d), telles que publiées par

Amirilargani et al.57 ...................................................................................................... 15

Figure 1.5 : Comparaison des masses molaires obtenues par ADMET avec les

catalyseurs de Grubbs deuxième génération et Hoveyda – Grubbs dans différents

solvants63 ....................................................................................................................... 19

Figure 1.6: Composants basiques d’un spectromètre MALDI-TOF utilisable en mode

linéaire et mode réflectron72 .......................................................................................... 26

Figure 1.7: Mesure de l’angle de contact ..................................................................... 28

Figure 1.8: Principe de mesure de l’angle de contact .................................................. 29

Figure 2.1: 1H-NMR spectrum of the representative monomer and polymers obtained

by ADMET: (a) PA-4EES, Mn = 2200 g mol-1 and (b) enlargement showing end-

groups for PA-4EES with two different molecular weights and for the monomer. ...... 54

Figure 2.2: Thermal stability of representative 4-ring and 8-ring polymers as

determined by thermogravimetry. ................................................................................. 58

Figure 2.3: Differential scanning calorimetry: (a) heating and cooling scans for PA-

4EES and (b) first heating scan for representative polymers ........................................ 59

Figure 2.4: X-ray diffraction diagrams of PA-4EES as recrystallized by evaporation

from various solvents .................................................................................................... 63

Figure 2.6: Molecular models of chain folding due to allyl groups: (a) chain fold

models and (b) extended chain conformation, showing deviation from linearity......... 68

Figure 2.7: Investigation of the double melting behaviour of PA-4EES ..................... 69

a) Representative DSC scans of PA-4EES and b) X-ray diffraction diagrams as

synthesized and after Annealing between Tm1 and Tm2 and rapid quenching ............... 69

Figure 3.1: 1H-NMR spectra of poly(6EES-ran-4EEScb) random copolymers........... 88

Figure 3.2: Representative MALDI-TOF mass spectrum of synthesized copolymers

a) PEES homopolymer b) Poly(4EES-alt-cb) and c) Poly(6EES-ran-4EEScb), ratio

70/30 .............................................................................................................................. 90

Figure 3.3: Thermogravimetric degradation curves of poly(4EES-alt-cb) (0/100),

PEES homopolymer (100/0) and random copolymers with varying 6EES/4EEScb

ratios ............................................................................................................................ 100

Figure 3.4: DSC curves of poly(4EES-alt-cb) (0/100), PEES homopolymer (100/0)

and random copolymers with varying 6EES/4EEScb ratios ....................................... 103

Figure 3.5: Changes in glass transition temperatures with varying 6EES weight % in

poly(6EES-ran-4EEScb) copolymers ......................................................................... 104

Figure 3.6: FTIR spectra of poly(6EES-ran-4EEScb) copolymer before and after

immersion in bleach: a) from 500 to 1900 cm-1 and b) from 2600 ............................ 106

xii

Figure 4.1: FTIR spectra of poly(4EES-alt-cb) and poly(4EES-alt-cb)-graft-PEG2: a)

from 700 to 1900 cm-1 and b) from 2500 to 4000 cm-1 .............................................. 130

Figure 4.2: 1H-NMR spectra of Poly(4EES-alt-cb) and Poly(4EES-alt-cb)-graft-

PEG2 ............................................................................................................................ 131

Figure 4.3: FTIR spectra of Poly(6EES-ran-4EEScb) and Poly(6EES-ran-4EEScb)-

graft-PEG16 a) from 700 to 1900 cm-1 and b) from 2500 to 4000 cm-1 .................... 133

Figure 4.4: 1H-NMR spectra of Poly(6EES-ran-4EEScb) and Poly(6EES-ran-

4EEScb)-graft-PEG16 .................................................................................................. 133

Figure 4.5: Contact angles of PES, PEES, alternate copolymer (Poly(4EES-alt-cb)),

and alternate copolymer after cross-linking or grafting .............................................. 136

Figure 4.6: Contact angles of the random copolymer (Poly(6EES-ran-4EEScb)) before

and after grafting or cross-linking ............................................................................... 137

Figure 4.7: FTIR spectra of Poly(6EES-ran-4EEScb) before and after surface-cross-

linking ......................................................................................................................... 139

Figure A.2.1: NMR spectra of 4,4’-bis(4-methoxyphenoxy) diphenyl sulfone (MPDS)

in CDCl3 ..................................................................................................................... 153

Figure A.2.2: NMR spectra of 4,4’-bis(4-hydroxyphenoxy) diphenyl sulfone (HPDS)

in DMSO ..................................................................................................................... 154

Figure A.2.3: NMR spectra of 4,4’-bis(4-allyloxyphenoxy) diphenyl sulfone (APDS)

in CDCl3 ...................................................................................................................... 155

Figure A.2.4: 1H-NMR spectrum of a) (Z)-1,4-dichlorobut-2-ene in CDCl3 and b) (E)-

1,4-dichlorobut-2-ene in CDCl3 .................................................................................. 156

Figure A.2.5: NMR spectra of 4-fluoro-4’-hydroxy diphenyl sulfone (FHDS)........ 157

Figure A.2.6: NMR spectra of 4-fluoro-4’-methoxy diphenyl sulfone (FMDS) ...... 158

Figure A.2.7: NMR spectra of 4,4'-bis(4-(4-(4-

methoxyphenylsulfonyl)phenoxy)phenoxy) diphenyl sulfone (MPSPPDS) in

CDCl3 .......................................................................................................................... 159


hydroxyphenylsulfonyl)phenoxy)phenoxy) diphenyl sulfone (HPSPPDS) in

DMSO ......................................................................................................................... 160

Figure A.2.9: 1H-NMR spectrum of poly(allyl-co-ether ether sulfone ether) (PA-

4EES) in CDCl3 .......................................................................................................... 161

Figure A.2.10: 1H-NMR of the 4-ring polymers obtained by polycondensation ....... 165

Figure A.2.11: Comparison of PTA-4EES NMR spectra before and after heating,

showing the persistence of the trans signals ............................................................... 166

Figure A.3.1: Representative MALDI-TOF mass spectrum of Poly(6EES-ran-

4EEScb), ratio 50/50 ................................................................................................... 168


4EEScb), ratio 60/40 ................................................................................................... 168


4EEScb), ratio 80/20 ................................................................................................... 169


4EEScb), ratio 90/10 ................................................................................................... 169

Figure A.4.1: NMR spectra of S-2-(2-(2-hydroxyethoxy)ethoxy)ethyl thioacetate in

CDCl3 ......................................................................................................................... 170

xiii

Figure A.4.2: NMR spectra of 2-(2-(2-hydroxyethoxy)ethoxy)ethanethiol in

CDCl3 .......................................................................................................................... 171

Figure A.4.3: FTIR spectra of Poly(6EES-ran-4EEScb) and Poly(6EES-ran-4EEScb)-

graft-C8 a) from 700 to 1900 cm-1 and b) from 2500 to 4000 cm-1 ........................... 172

Figure A.4.4: 1H-NMR spectra of Poly(6EES-ran-4EEScb) and Poly(6EES-ran-

4EEScb)-graft-C8 ........................................................................................................ 173

Figure A.4.5: FTIR spectra of Poly(4EES-alt-cb) and Poly(4EES-alt-cb)-crosslink-

Pr ................................................................................................................................. 174

a) from 700 to 1900 cm-1 and b) from 2500 to 4000 cm-1 .......................................... 174


PEG2 a) from 700 to 1900 cm-1 and b) from 2500 to 4000 cm-1 ................................. 175

xiv

Abréviations

Å : Ångström

ADMET : Polymérisation par métathèse des diènes acycliques (acyclic

diene metathesis polymerization)

alt : Alternate

APDS : 4,4’-Bis(4-allyloxyphenoxy) diphenyl sulfone

BBr3 : Tribromure de bore

cb : cis but-2-ène

CDCl3 : Chloroforme deutérié

CHCl3 : Chloroforme

CH2Cl2 : Dichlorométhane

CH3I : Iodure de méthane

Cl : Chlore

C8 : Octane

d : Doublet

dd : Doublet de doublet

DMAc : N,N-Diméthylacétamide

DMF : N,N-Dimethyformamide

DMPA : 2,2-diméthoxy-2-phénylacetophénone

DMSO : Diméthylsulfoxyde

DMSO-d6 : Diméthylsulfoxyde deutérié

DP : Degré de polymérisation

DSC : Calorimétrie différentielle à balayage ou analyse

enthalpique différentielle

E-DCB : (E)-1,4-dichlorobut-2-ène

EES : Éther éther sulfone

EESE : Éther éther sulfone éther

EG : End-group

FHDS : 4-Fluoro-4’-hydroxy diphenyl sulfone

FMDS : 4-Fluoro-4’-methoxy diphenyl sulfone

FTIR : Spectroscopie infrarouge à transformée de Fourier

FTIR-ATR : Spectroscopie infrarouge par réflexion totale atténuée

G2 : Catalyseur de Grubbs de deuxième génération (Grubbs

second generation catalyst)

H : Hydrogène ou proton

HCl : Acide chlorhydrique

HG : Hoveyda–Grubbs catalyst

HPDS : 4,4’-Bis(4-hydroxyphenoxy) diphenyl sulfone

HPSPPDS : 4,4’-Bis(4-(4-(4-hydroxyphenylsulfonyl)phenoxy)phenoxy)

diphenyl sulfone

I : Intensité

Ip : Indice de polydispersité

IR : Infrarouge

xv

K2CO3 : Carbonate de potassium

KOH : Solution aqueuse d’hydroxyde de potassium

kV : kilovolt

Li : Lithium

m : Multiplet

M : Molaire

mA : milliampère

MALDI-TOF : Matrix-Assisted Laser Desorption Ionization –Time Of

Flight

MEB : Microscopie Électronique à Balayage

mg/mL : Milligramme par millilitre

MgSO4 : Sulfate de magnésium

MHz : Méga Hertz

mL : Millilitre

mmol : Millimole

Mn : Masse molaire moyenne en nombre

MPa : Mégapascal

MPDS : 4,4’-Bis(4-methoxyphenoxy) diphenyl sulfone

MPSPPDS : 4,4’-Bis(4-(4-(4-methoxyphenylsulfonyl) phenoxy)pentoxy)

diphenyl sulfone

Mw : Masse molaire moyenne en poids

m/z : Ratio masse sur charge

NaCl : Chlorure de sodium

NaI : Iodure de sodium

NaOH : Hydroxyde de sodium

NaHCO3 : Bicarbonate de sodium

nm : Nanomètre

NMP : N-Méthyl-2-pyrrolidone

PA-4EES : Poly(allyl-co-ether ether sulfone ether )

PABr-4EES : Poly(brominated allyl-co-ether ether sulfone ether)

PACl-4EES : Poly(chlorinated allyl-co-ether ether sulfone ether)

PAE-4EES : Poly(trans-allyl-co-ether ether sulfone ester)

PAH-4EES : Poly(hydrogenated allyl-co-ether ether sulfone ether)

PAN : Polyacrylonitrile

PCA-4EES : Poly(cis-allyl-co-ether ether sulfone ether)

PEG : Polyéthylène glycol

PEEK : polyétheréthercétone

PEES : Polyétheréthersulfone

PES : Polyéthersulfone

PPTA : Poly(para-phénylène térephthalamide)

ppm : Partie par million

Pr-dithiol : Propanedithiol

PTA-4EES : Poly(trans-allyl-co-ether ether sulfone ether)

ran : Random

RMN : Résonance magnétique nucléaire

xvi

RMN 13C : Résonance magnétique nucléaire du carbone 13

RMN 1H : Résonance magnétique nucléaire du proton

s : Singulet

SEC : Chromatographie d’exclusion stérique

SEM : Scanning Electron Microscopy

t : Triplet

tb : trans but-2-ène

Tg : Température de transition vitreuse

TGA : Analyse thermogravimétrique

Tm : Température de fusion

TMS : Tetraméthysilylane

UV : Ultraviolet

WAXS : «Wide Angle X-ray Scattering» ou diffraction des rayons X

aux grands angles

Z-DCB : (Z)-1,4-dichlorobut-2-ène

xvii

Symboles

𝑑𝑠 : Densité du solvant g/cm3

𝑑𝑝 : Densité du copolymère en g/cm3

𝑀𝑐 : Masse molaire moyenne en nombre entre les ponts de réticulation

𝑀𝑠 : Masse molaire du solvant g/mol 𝑚𝑝 : Masse du copolymère avant gonflement

𝑚𝑡 : Masse du copolymère à l’équilibre après gonflement (copolymère +

solvant)

𝑅 : Constante des gaz parfaits

𝑇 : Température absolue

𝑉𝑠 : Volume molaire du solvant en cm3/mol

𝑉𝑝 : Fraction volumique du copolymère à l’équilibre après absorption

du solvant

𝑉𝑝𝑟 : Fraction volumique du copolymère réticulé

𝛽 : Constante de réseau

𝛿 : Paramètre de solubilité

𝜒 : Paramètre d’interaction solvant/copolymère

𝜒𝐷𝑆𝐶 : Taux de cristallinité obtenu par DSC

𝜒𝑋−𝑟𝑎𝑦 : Taux de cristallinité obtenu par diffraction des rayons X

𝜌 : Densité du copolymère g/cm3

θ : Thêta

% : Pourcentage

° : Degré

°C : Degré Celsius

°C/min : Degré Celsius par minute

𝛥𝐻 : Enthalpie de fusion

xviii

Dédicaces

Je dédie ce mémoire à :

Ma mère, qui a œuvré pour ma réussite, de par son amour, son soutien, tous les

sacrifices consentis et ses précieux conseils, pour toute son assistance et sa présence

dans ma vie, reçois à travers ce travail aussi modeste soit-il, l'expression de mes

sentiments et de mon éternelle gratitude.

Mon père, qui peut être fier et trouver ici le résultat de longues années de sacrifices et

de privations pour m'aider à avancer dans la vie. Puisse Dieu faire en sorte que ce

travail porte son fruit ; Merci pour les valeurs nobles, l'éducation et le soutien

permanent venu de toi.

Mes frères et sœurs (Jacqueline, Diory, Rose, Sobel, Mane, Mbalam, Watéo, Mame

Coumba, Mame Latsouck et Marie Ngounda et à mes demi-frères et demi-sœurs

(Diouly, Gnilane et Sara) qui n'ont cessé de m’encourager et d'être pour moi des

exemples de persévérance et de courage.

La femme de ma vie, Salimata Ndiaye, mon âme sœur, la lumière de mon chemin.

Ma vie à tes cotés est remplie de belles surprises. Tes sacrifices, ton soutien moral et

matériel, tes encouragements sans cesse, ta gentillesse sans égal, ton profond

attachement m'ont permis d’arriver au bout de ce travail.

xix

« Telle est bien la beauté et la

noblesse de la science : désir sans

fin de repousser les frontières du

savoir, de traquer les secrets de la

matière et de la vie sans idée

préconçue des conséquences

éventuelles. »

Marie Curie

xx

Remerciements

Je souhaite adresser mes remerciements les plus sincères à toutes les personnes qui

ont contribué de prêt ou de loin à la réussite de cette thèse.

Nulle œuvre n'est exaltante que celle réalisée avec un soutien moral et financier.

D’abord, je remercie ma Directrice de thèse, la Professeure Josée Brisson, de m’avoir

donné l’opportunité d’intégrer son groupe de recherche, de m’avoir soutenu et permis

d’explorer le domaine fascinant de la synthèse des polymères et de leurs

caractérisations. Vous ne cessiez pas de m’encourager, encore m’encourager, toujours

m’encourager à aller jusqu’au bout de mes synthèses pour l’obtention de copolymères

de hautes masses molaires. Vos nombreux conseils, votre imagination et votre

énergie tout au long de ce travail ont été, pour moi, une véritable source de

motivation afin de mener à bien ce projet. J'aimerais également lui dire à quel point

j’ai apprécié sa grande disponibilité tout au long de cette thèse plus particulièrement

durant les moments de correction des articles et de ce document. Enfin, j’ai été

extrêmement sensible à ses qualités humaines, d'écoute et de compréhension tout au

long de ce travail doctoral.

Je souhaite continuer à la côtoyer dans le futur aussi bien dans le cadre professionnel

que personnel.

J’adresse également mes remerciements au Professeur Jean-François Morin pour ses

conseils et pour m’avoir permis d’opérer les réactions thiol-ène clic dans son

laboratoire, mais aussi, pour avoir accepté de faire partie des membres du jury.

Mes remerciements vont également à la Professeure Maria-Cornelia Iliuta pour avoir

mis, à ma disposition, les équipements de son laboratoire et de m’aider à procéder

aux mesures d’angles de contact.

Je sais infiniment gré au Professeur Jérôme Claverie de l’UQAM de s’être rendu

disponible et d’avoir accepté la fonction d’examinateur externe pour cette thèse.

xxi

Je suis particulièrement reconnaissant au Professeur Peter McBreen de l’intérêt qu’il

a porté à l’égard de ce travail en acceptant de faire partie du jury.

Mes remerciements vont également à Madame Plesu (TGA, DSC, SEC, Rayons X),

Monsieur Audet (RMN), Monsieur Groleau (CHNS), Monsieur Paquet-Mercier

(FTIR) et Madame Furtos de l’Université de Montréal (MALDI-TOF).

Je tiens à remercier vivement tous les membres du groupe de la Professeure Brisson :

Huan Liang, Abdelkader Benhalima, Simon Provencher, François Hudon et Marianne

P. Ouattara. Mention spéciale à Huan Liang, avec qui, j’ai mené des discussions

enrichissantes en ce qui concerne nos projets. Je voudrais remercier particulièrement

les étudiants stagiaires : Mikaël Leduc qui a participé à l’optimisation du choix du

solvant utilisé pour la recristallisation des copolymères présentés dans le chapitre 2 et

Jacob Dion Gagné, pour son aide à la préparation des films de polymère.

Enfin, ces remerciements ne peuvent s’achever sans une pensée particulière pour tous

mes proches et amis qui m’ont toujours soutenu et encouragé dans les bons comme

dans les moments plus difficiles. Merci à toutes et tous !

xxii

Avant-propos

Cette thèse a été rédigée sous la direction de Madame Josée Brisson, Professeure

titulaire au département de chimie de l’Université Laval. En étroite collaboration avec

ma directrice de recherche, j’ai joué un rôle de premier plan dans la synthèse et la

caractérisation des copolymères ainsi que dans la rédaction des articles et de ce

document.

Cette thèse comprend cinq chapitres. Le premier et le cinquième chapitre décrivent

respectivement l’introduction générale et la conclusion générale. Les chapitres 2, 3, et

4 ont chacun fait l’objet d’un document sous forme d’article qui a été publié ou sera

soumis pour publication dans une revue scientifique. Pour chacun de ces articles, j’ai

œuvré comme auteur principal en procédant aux synthèses et à la majeure partie des

caractérisations des copolymères, en rédigeant la première version des articles, en

apportant les modifications suggérées par la professeure Brisson pour tous les

articles, mais également, celles suggérées par les arbitres de l’article dans le cas du

Chapitre 2.

Les co-auteurs de ces manuscrits ont largement contribué à leur réalisation en

participant à l’optimisation de certaines méthodes de caractérisation ou en procédant

à leur révision, en plus des conseils et des orientations. Tous mes remerciements à :

Mikaël Leduc (Chapitre 2), qui a participé à l’optimisation du choix du solvant

utilisé pour la recristallisation des copolymères.

Alexandra Furtos (Chapitre 3), qui nous a aidé dans l’enregistrement des spectres

MALDI-TOF et a confirmé notre interprétation

Jean-François Morin (Chapitre 4), qui a proposé certaines voies ou conditions de

synthèse, notamment pour les synthèses thiol-ène clic.

Maria Cornelia Iliuta (Chapitre 4), qui nous a assisté dans l’enregistrement des

mesures d’angles de contact et dans leur interprétation.

xxiii

Hormis les articles scientifiques, ce travail a fait l’objet de plusieurs présentations

dans des conférences nationales et internationales qui sont les suivantes:

A. Faye, J. Brisson, Synthesis and postfunctionalization of polyetherethersulfone-

allyl copolymers for applications in membrane filtration, Sustainable Materials

Science and Technology, Paris, France, juillet 2015.

A. Faye, J. Brisson, Synthesis and crystallization control of polyetherethersulfone

copolymers by regular insertion of an allyl functionality, High Polymer Forum,

Gananoque, Canada, juillet 2014.

A. Faye, J. Brisson, Synthesis Route for Crystalline Polyethersulfone Copolymers,

96th Canadian Chemistry Conference and Exhibition, Quebec, Canada, mai 2013.

A. Faye, J. Brisson, Synthesis of Polyethersulfone Copolymers via ADMET, High

Polymer Forum, Gananoque, Canada, août 2012.

1

Chapitre 1 : Introduction générale

Les polyéthersulfones (PES) sont des polymères amorphes de la famille des

poly(arylène éther sulfone)s et dont la structure chimique est composée de noyaux

aromatiques liés à des groupements sulfonyles (-SO2-) et éthers (-O-) (Schéma 1.1).

Les groupements phényles et sulfones sont responsables de la résistance à la chaleur

et à l'oxydation, tandis que les éthers contribuent beaucoup à la flexibilité de la

chaîne.

Schéma 1.1 : Formule chimique du PES

L’unité de répétition, bien qu’étant régulière, ne permet pas d’obtenir facilement des

arrangements ordonnés en raison de l’alternance des groupements éther et sulfone,

chacun ayant un angle de valence différent, ce qui nuit à un empilement de chaîne

régulier.1,2 La forte polarité des liaisons sulfones conduit à un effet d’attraction

d'électrons qui délocalise les électrons π des noyaux aromatiques, ce qui a tendance à

donner un caractère de double liaison aux liaisons C-S de la chaîne. Une telle

délocalisation augmente considérablement la barrière de rotation autour des liaisons

C-S et par conséquent la rigidité de la chaîne, 3 gênant ainsi leur repliement. Cette

rigidité intrinsèque de la chaîne a également pour conséquence de rendre élevées les

températures de transition vitreuse (Tg) de ces matériaux (230 °C environ).4

D’autre part, l'angle de valence C-S-C est de 105° alors que celui entre C-O-C est de

121°.5 Cette différence substantielle dans les angles de liaison réduirait la densité

d’empilement des chaînes. Ceci entraîne une diminution de l'enthalpie de fusion et de

la température de fusion (Tm).6 En conséquence, l'intervalle (Tm-Tg) est assez étroit

et la cristallisation est inhibée.

2

Dans cette même famille de polymères, on rencontre le polysulfone (PSF) et le

poly(phényl sulfone) (PPSF) qui ont été commercialisés sous différents noms (voir le

Tableau 1.1) et le poly(éther éther sulfone) (PEES).

Tableau 1.1 : Famille des polyéthersulfones avec leurs abréviations, structures

chimiques, noms commerciaux, producteurs et années de synthèse1

Abréviations Structures chimiques Noms Producteurs Années

PES

Victrex ICI 1972

PSF

Udel UCC 1965

PPSF

Radel UCC 1976

PEES

- - -

1.1 Revue de la littérature sur la synthèse des PES

Les PES ont été synthétisés pour la première fois et de façon indépendante dans les

années 1960 par trois (3) laboratoires différents que sont : 3M Corporation7 et Union

Carbide Corporation (UCC),8,9 tous deux basés aux États-Unis et le Plastics Division

of ICI10 basé au Royaume Uni. L’objectif était de développer des matériaux

thermoplastiques thermiquement stables répondant à des applications d'ingénierie.11,12

Deux principales méthodes ont été utilisées pour la synthèse des PES. 3M

Corporation a synthétisé les PES par polysulfonylation du 4,4'-

bis(chlorosulfonyl)diphényle éther avec l’oxydibenzène en utilisant une réaction de

Friedel-Crafts,12 tel que montré dans le schéma 1.2, autrement dit en utilisant une

3

substitution électrophile aromatique.1 Cependant, cette méthode est peu sélective et

souffre d’une faible réactivité pour un tel substrat.13 Union Carbide Corporation,

quant à elle, a développé les PES par polyétherification en utilisant une réaction de

substitution nucléophile aromatique12 (Schéma 1.3). ICI a également utilisé la

substitution nucléophile aromatique pour la synthèse de ces polymères mais en

faisant réagir un sel de métal alcalin d’un composé 4-chloro-4’-hydroxy diphényl

sulfone sur lui-même pour obtenir un PES (Schéma 1.3a) ou bien un diphénolate de

métal alcalin avec un composé bis(4-chlorophényl) sulfone pour obtenir un PEES

(Schéma 1.4), en utilisant un solvant polaire aprotique comme le diméthyle sulfoxyde

(DMSO).1,6 Cependant, un léger excès de NaOH conduit à un clivage des chaînes du

polymère, ce qui entraîne l’obtention de polymères de faibles masses molaires.14 Par

la suite, des masses molaires élevées ont été obtenues en remplaçant le NaOH par le

K2CO3 en présence d’un solvant polaire aprotique de haut point de fusion comme le

sulfolane ou le diphényle sulfone mais à une température très élevée (335 °C).14,15

Schéma 1.2 : Synthèse des PES par polysulfonylation utilisée par 3M Corporation12

4

Schéma 1.3 : Synthèse des PES par polyétherification utilisée par Union Carbide

Corporation et ICI12

Schéma 1.4 : Synthèse des PEES par polyétherification utilisée par Plastics division

of ICI12

Les solvants polaires aprotiques, en plus de faciliter la solubilité du polymère,

permettent d’augmenter la nucléophilie de l’alcoolate en complexant les cations Na+

ou K+ si l’hydroxyde de potassium est utilisé à la place de l’hydroxyde de sodium,

augmentant ainsi le degré de dissociation.8 Les atomes d’halogène de ces composés

sont activés par le groupe sulfone (groupement fortement électro-attracteur) situé en

position para par rapport à l’halogène.8

La principale méthode utilisée pour la synthèse des PES est donc la polycondensation

par substitution nucléophile aromatique. Le mécanisme de substitution nucléophile

aromatique est présenté dans le Schéma 1.5. Dans un premier temps, le nucléophile

attaque le carbone porteur de l’halogène (C-X) activé par le groupement sulfone

(groupement fortement électroattracteur). L’halogène X ne part pas directement mais

il y a création d’un intermédiaire stabilisé par résonance appelé complexe de

5

Meisenheimer.12 La deuxième étape de réaction consiste à l’élimination du groupe

partant, X.

Les composés fluorés sont plus réactifs que les composés chlorés correspondants qui,

eux, sont plus réactifs que leurs analogues bromés car plus l’halogène est

électronégatif mieux il stabilise la charge négative de l’intermédiaire réactionnel

(complexe de Meisenheimer). L’attaque du nucléophile, dans le cas des composés

fluorés, est également favorisée par le caractère non volumineux (donc moins

encombrant) des atomes de fluor et la forte polarisation du lien Cδ+-F δ- due à leur

forte électronégativité qui augmente le caractère électrophile de l’atome de carbone.12

Schéma 1.5 : Mécanisme de substitution nucléophile aromatique

1.2 Les réactions thiol-ène clic radicalaires

Le terme chimie clic, introduit en 2001 par Sharpless et al.,16 décrit des couples de

groupements fonctionnels réagissant rapidement et sélectivement l’un avec l’autre

dans des conditions douces. Ces réactions chimiques ont pour caractéristiques d’être à

la fois modulables, régiosélectives, efficaces donnant des produits facilement

purifiables (isolation simple et non chromatographique de l’adduit obtenu) avec des

rendements élevés.16,17

Le terme thiol-ène clic est utilisé pour désigner l'addition d'un thiol sur une liaison

ène (double liaison).18 Les réactions thiol-ène clic radicalaires sont des réactions

photochimiques c’est-à-dire qui se déroulent sous l'action de la lumière. Les réactions

6

thiol-ène clic radicalaires ont l’avantage de combiner les attributs de la chimie clic et

d'une réaction photoamorcée (activation à des moments et des endroits spécifiques),

ce qui fait qu’elles sont des méthodes intéressantes pour la synthèse chimique de

matériaux avec des propriétés modulables.19,20 Ces réactions sont donc largement

utilisées dans les domaines des biosciences,21,22 de la chimie médicinale23 et de la

chimie des matériaux.24 Dans la chimie des matériaux polymères, elles sont utilisées

pour faire une polymérisation, une modification de surface, un greffage de molécules

ou bien pour synthétiser des dendrimères.25 Comme pour tout procédé radicalaire, il

existe un certain nombre de moyens d'initiation des réactions thiol-ène clic. Ces

méthodes d’excitation sont largement discutées par Hoyle et al.20 Nous nous

limiterons au procédé d'excitation par clivage homolytique d’un photoiniateur comme

le 2,2-diméthoxy-2-phénylacetophénone (DMPA) qui est l’un des plus efficaces car

le rendement quantique pour la production de radicaux réactifs est plus élevé.20 Par

irradiation avec une lampe à rayons ultraviolets (UV) de longueur d’onde 365 nm, le

DMPA se clive facilement en générant deux radicaux A (radical benzoyle) et B

(radical (diméthoxyméthyl) benzène) (Schéma 1.6). Le radicale B se réarrange pour

former un radical méthyle et le benzoate de méthyle.20,26 Les radicaux A et méthyle

ont une affinité très grande pour l’hydrogène et donc peuvent facilement arracher un

hydrogène d’un thiol donnant naissance à un radicale thiyle très réactif.27 Le radical

thiyle formé réagit ensuite avec la double liaison dans une configuration anti-

Markovnikov pour donner un thiolalkyle radical. Ce dernier capte un hydrogène d’un

thiol conduisant ainsi à la formation d’un thioéther et d'un nouveau radical thiyle qui

peut réagir de nouveau avec une double liaison (Schéma 1.7).18,25,27

7

Schéma 1.6 : Mécanisme radicalaire du DMPA26

Schéma 1.7 : Mécanisme de la réaction thiol-ène clic18,25,27

1.3 Domaine d’application des PES

Les polyéthersulfones (PES) et polyétheréthersulfones (PEES), avec un éther de plus

(Tableau 1.1), sont des polymères qui suscitent un grand intérêt dans la fabrication de

dispositifs de haute technologie non seulement du fait de leur haute performance

thermique, chimique et radiative6,28,29 mais également de la possibilité pour le

chimiste de modifier les propriétés chimiques et physiques de ces polymères pour les

8

adapter à des besoins particuliers. Les dispositifs constitués par ces matériaux ont un

excellent comportement mécanique face aux températures élevées, ils sont également

très résistants aux chocs, au feu et à l’hydrolyse.30-32 La principale application de ces

polymères réside dans la fabrication de membranes pour la filtration. Les

polyéthersulfones sont d’excellents candidats pour la fabrication de membranes pour

la microfiltration ou l’ultrafiltration car :33,34

- ils permettent d’avoir une grande sélectivité de la membrane (taux de rejet élevé)

et une bonne distribution de la taille des pores ;

- ils sont très résistants à l’oxydation par les désinfectants tels que les peroxydes ou

l'hypochlorite souvent nécessaires pour le nettoyage des membranes après

utilisation ;

- ils présentent un excellent comportement thermique, résistant jusqu’à 400 °C, avec

des températures de transition vitreuse qui atteignent les 200 °C4 due à la rigidité

intrinsèque de la chaîne (présence de noyaux aromatiques)3,4,35 et peuvent être

utilisés sur un large domaine de pH ;

- ils possèdent des propriétés mécaniques intéressantes qui permettent de résister

aux gradients de pression utilisés comme force motrice de transfert lors des

opérations de filtration.

Les premières membranes à base de PES ont été obtenues avec le polysulfone (PSF)

au cours des années 1960 pour une alternative aux membranes cellulosiques dans des

procédés de séparation, en raison de leur résistance très élevée dans des conditions

extrêmes de pH et une bonne stabilité thermique.36 De nos jours, les applications

existantes se situent principalement dans la fabrication de membranes pour des filtres

de seringue utilisés pour la filtration de solutions à l’échelle du laboratoire ou bien

pour des applications dans le domaine industriel pour des membranes à fibres creuses.

Dans l’industrie laitière, par exemple, ces membranes ont permis de valoriser le

coproduit majeur dans la fabrication du fromage, le lactosérum communément appelé

petit lait (Figure 1.1). Le lactosérum a été considéré pendant longtemps comme

9

déchet dans l’industrie fromagère, mais aujourd’hui, grâce à ces membranes, il est

possible de le fractionner en plusieurs constituants individuels de haute qualité

nutritive (concentrés de protéines, isolats de protéines, …).

Figure 1.1 : Filtration du lait caillé pour la production du fromage

(adapté à partir de la page web du Comité de défense du véritable camembert,

http://veritable.camembert.free.fr/pages/Lait_traitements.htm, consultée le 17 janvier

2016)

On se sert également de ces membranes de PES pour la production industrielle d’eau

potable, à travers un procédé sûr, efficace et rapide pour l'élimination des particules,

de la turbidité et des micro-organismes présents dans l'eau.

Les deux niveaux de filtration membranaire les plus utilisés pour les PES sont la

microfiltration et l’ultrafiltration.1,37,38

La microfiltration, pour laquelle la taille des pores de la membrane est de l’ordre du

micromètre et se situant généralement entre 0,1 à 10 μm, permet d’éliminer les

matières en suspension et de faire l’épuration bactérienne.

L’ultrafiltration, avec une taille des pores de la membrane variant de 1 à 100 nm, en

plus de l’épuration bactérienne, permet d’éliminer les virus.

http://veritable.camembert.free.fr/pages/Lait_traitements.htm

http://www.futura-sciences.com/magazines/sante/infos/dico/d/medecine-bacterie-101/

10

D’autre part, il est possible de moduler les propriétés de ces polymères pour les

adapter à une application bien définie en greffant certains groupements sur la chaîne

polymère.7,14 Les polyéthersulfones dont des groupements sulfones sont rajoutés sur

les cycles aromatiques sont utilisés comme membranes échangeuses d’ions dans les

piles à combustible pour des applications dans le domaine du transport (véhicules,

camions, autobus et locomotives) et l'électronique.39,40

Du fait de la résistance de ces matériaux à l’eau et à la vapeur, ils sont utilisés pour

fabriquer des ustensiles de cuisson et du matériel médical (nébuliseurs et composants

de dialyse).1 Ils ont aussi des applications dans le domaine nucléaire, des

télécommunications, des pièces automobiles ou aérospatiales pour l’isolation de

câbles.14

1.3.1 Filtration membranaire

Une membrane de filtration est un matériau à perméabilité sélective qui permet de

séparer des particules en solution en fonction de leur taille sous l'action d'une force

motrice, le but étant de purifier un liquide ou de fractionner ou concentrer des

particules. Les particules retenues au niveau de la surface de la membrane forment le

rétentat tandis que celles qui la traversent représentent le perméat (Figure 1.2).

Figure 1.2 : Principe d’une membrane de filtration selon Prulho41

11

Il existe deux modes de filtration, les filtrations frontale et tangentielle, que l’on

différencie selon l’orientation du flux d’alimentation.

En mode frontal (filtration la plus connue), le flux d’alimentation est perpendiculaire

à la membrane alors que dans le cas d’une filtration tangentielle, le flux arrive

parallèlement à la membrane. La tangentielle permet un colmatage moins rapide, mais

elle est généralement réservée à la filtration de très petites particules.

La majorité des membranes polymères poreuses commercialisées sont

élaborées via un procédé de séparation de phases. La séparation de phases (également

appelée inversion de phase ou démixtion) résulte d'un changement d'état

thermodynamique d'une solution de polymère initialement homogène. Le changement

d'état thermodynamique peut être induit par différentes méthodes :42

- variation de la température ;

- intrusion d'un non-solvant dans une solution binaire polymère/solvant.

Tous les processus de séparation de phases sont basés sur les mêmes principes

thermodynamiques. Dans tous les cas, le point de départ est une solution

thermodynamiquement stable soumise ensuite à des conditions entraînant une

démixtion telle qu'un abaissement de température ou l'intrusion d'un non-solvant.

L'inversion de phase induit la création de deux phases : une phase pauvre et une

phase riche en polymère qui croissent suivant des mécanismes de nucléation-

croissance pour former l'architecture membranaire.42 Après démixtion liquide-liquide,

la phase riche en polymère se solidifie et constitue alors la matrice membranaire. La

phase pauvre est éliminée par des lavages successifs et laisse place aux pores de la

membrane.

1.4 Problématique

Les polyéthersulfones sont utilisés dans plusieurs domaines, cependant l’obtention de

voies de synthèse permettant un meilleur contrôle de leur masse moléculaire, leur

morphologie et leurs propriétés thermiques reste toujours un défi pour les chercheurs.

12

La polycondensation par substitution nucléophile aromatique est la principale

méthode utilisée pour la synthèse des PES. Cette polycondensation est effectuée en

système ouvert en déplaçant l'équilibre de la réaction par élimination de la petite

molécule formée lors de la réaction. Cette élimination devient de plus en plus difficile

au fur et à mesure que la réaction avance du fait de la vitesse de diffusion de ces

petites molécules, ce qui rend peu probable les possibilités de contrôle de la masse

molaire. Ce type de polymérisation ne permet pas, non plus, de contrôler la

morphologie et les propriétés thermiques. Le contrôle de ces paramètres pourrait

jouer un rôle déterminant dans l’amélioration des propriétés pour des applications

déjà existantes, mais pourrait aussi permettre de répondre à des besoins additionnels,

notamment la modulation des propriétés séparatrices des membranes.

La principale application des PES se situe dans la fabrication de membranes,

cependant leur utilisation comme membranes est souvent limitée par leur caractère

hydrophobe qui, par l’adsorption de particules au niveau de la surface, entraîne un

encrassement de la membrane conduisant ainsi au colmatage.28,43 Le colmatage

résulte de l’accumulation des substances filtrées au niveau de la surface de la

membrane ou à l’intérieur des pores et, entraîne une perte des performances des

membranes. Les causes du colmatage des membranes à base de PES peuvent

provenir de trois origines principales :44

- Le colmatage par adsorption : Il provient de la fixation de particules au niveau

de la surface de la membrane et résulte en général des interactions entre les

molécules notamment les protéines que contiennent les liquides filtrés et les

surfaces hydrophobes de la membrane. Le degré d'adsorption dépend du type

d'interaction tel que les liaisons hydrogène, les interactions dipolaires, les

interactions de van der Waals, et les effets électrostatiques.45 Cependant, il a été

rapporté que les interactions hydrophobes sont le principal facteur renforçant

l'adsorption des protéines sur la surface des membranes à base de

polyéthersulfone.46 Quand une molécule de protéine est en contact avec la surface

d’une membrane hydrophobe, les molécules d'eau liées à la protéine vont se

déplacer du fait des interactions hydrophobes. Ceci provoque une rupture de la

13

liaison entre la protéine et les molécules d’eau, induisant des changements de

conformation dans la structure de la protéine, ce qui se traduit par une adsorption

irréversible de la protéine sur la surface de la membrane.47,48

- La capture de particules : Elle intervient lors de la filtration uniquement et se

caractérise par le blocage de particules dans les pores de la membrane par effet

stérique sous l’effet de la force motrice.49

- La création de biofilms : Elle intervient lorsque des bactéries se développent à la

surface de la membrane sous l’effet de conditions favorables à leur développement

(température notamment), et en particulier dans les zones de faibles convections.

Les bactéries sécrètent des exopolymères qui forment un film peu perméable

recouvrant la surface de la membrane.

Des observations réalisées par le groupe de Qilin Li50 au microscope électronique à

balayage (MEB) ont permis de mettre en évidence la présence d’un agrégat de

particules à la surface de la membrane après ajout de particules organiques dans les

solutions filtrées (Figure 1.3). Ce dépôt de matières organiques, adhérant au matériau

membranaire, induit des chutes importantes du flux de perméation et, en raison de

leur croissance, il est difficile de les éliminer par la suite. Un rétrolavage à l’eau

seulement n’est plus suffisante pour retrouver la perméabilité optimale de la

membrane. Un nettoyage chimique est donc nécessaire. Par exemple, la soude

caustique associée à de l’hypochlorite de sodium (NaClO/NaOH) permet de

solubiliser la matière organique composée de groupement phénol ou carboxyle et

dégrader les polysaccharides et protéines en sucres et composés aminés plus

petits.51,52 Les lavages acides permettent d’éliminer des espèces cationiques.53

L’impact des lavages chimiques sur l’intégrité membranaire est encore peu étudié,

cependant il a été montré qu’à long terme ces lavages chimiques peuvent entraîner

une modification du matériau membranaire et aggraver le colmatage.54

14

Figure 1.3 : Images MEB en coupe plane (a) et transversale (b) d’une membrane

colmatée (agrégat de particules encerclé en vert) 50

Pour réduire cet effet, il est rapporté dans la littérature qu’il faudrait augmenter

l’hydrophilicité de ces polymères pour améliorer les propriétés anti-adsorbantes des

membranes, ce qui limitera considérable le colmatage et ainsi maintenir les

performances de la membrane.48,55,56

Il est également rapporté que les membranes hydrophiles sont plus faciles à nettoyer

que les membranes hydrophobes car l’adsorption devient faible et donc facile à

enlever.

Une des stratégies visant à améliorer l'hydrophilicité de ces polymères est de les

mélanger avec d’autres polymères hydrophiles comme les polyéthylènes glycols

(PEG), mais cette méthode a des limites car à un certain rapport massique, la solution

de polymère devient hétérogène conduisant à la séparation de phases lors de la

fabrication de la membrane. Le groupe de Mohammadi57 a montré qu’en mélangeant

le PES avec le polyacrylonitrile (PAN) dans un rapport massique de 70/30, il apparaît

deux couches au niveau de la membrane vue au microscope électronique à balayage

(MEB) due à la séparation de phase lors de sa fabrication (Figure 1.4). Cette

séparation modifie considérablement la structure de la membrane, comparée à celle

du PES.

Coupe plane Coupe transversale

a) b)

15

Figure 1.4 : Images MEB d’une coupe transversale d’une membrane de PES seul (a)

et d’un mélange PES/PAN dans un rapport massique 70/30 (d), telles que publiées

par Amirilargani et al.57

Pour les piles à combustible, le rajout des groupements sulfones sur les noyaux

aromatiques pose souvent un problème de stabilité. Zhang et al.40 ont rapporté qu’il

est généralement considéré que les polymères avec des groupes acides sulfoniques

pendants ou des chaînes latérales sont plus stables à l'hydrolyse que ceux avec des

groupes acides sulfoniques directement connectés sur le squelette des polymères.

I.5 Objectif du projet

Dans cette présente étude, notre objectif est de synthétiser les PES avec incorporation

de segments flexibles comportant des doubles liaisons dans les chaînes du polymère

pour contrôler :

- la cristallinité ;

- les températures de transition vitreuse ;

- l’hydrophilicité des copolymères obtenus.

La modulation de la cristallinité est effectuée en introduisant, au sein de la chaîne, un

groupement allyl flexible, de configuration cis ou de configuration trans. Ces

segments flexibles pourraient provoquer un repliement de chaînes à l’image des

travaux du groupe de Josée Brisson58 sur des copolymères rigides flexibles de Kevlar

où il est indiqué que la présence d’une chaîne flexible permet le repliement des

chaînes de polymères rigides, mais pourraient aussi, si le bloc rigide est de taille assez

faible, être incorporés au sein de l’unité de répétition et de la maille cristalline. Le

16

changement de configuration permettra alors d’obtenir une chaîne de symétrie et de

conformation différentes, ce qui devrait provoquer le changement de cristallinité

désiré.

Les températures de transition vitreuse sont contrôlées par la modulation du

pourcentage de segment flexible incorporé dans les chaînes du polymère.

Les doubles liaisons incorporées sont utilisées pour une post-fonctionnalisation,

permettant de contrôler l’hydrophilicité enfin d’adapter les propriétés des

copolymères à des applications bien définies. Par exemple, pour lever les contraintes

d’application des PES (leur caractère hydrophobe) dans les membranes de filtration,

leur hydrophilicité est modulée en fonctionnalisant les copolymères obtenus à travers

les doubles liaisons incorporées par le greffage de différentes molécules hydrophiles.

L’ajout des segments flexibles permettra éventuellement d’améliorer la solubilité de

ces matériaux et de faciliter leur mise en œuvre.59 Cependant, leur ajout provoque une

baisse des températures de transition vitreuse.59 C’est pourquoi la séquence, la taille

et la proportion de ces segments flexibles doivent être ajustées afin de minimiser leurs

effets sur les propriétés thermiques des matériaux résultants.

Pour l’introduction des segments flexibles dans les chaînes du polymère, une

méthodologie appropriée doit être utilisée pour arriver à l’objectif fixé. Deux

approches différentes sont donc utilisées dans ce projet : la polymérisation par

métathèse des diènes acycliques (ADMET en anglais, Acyclic Diene Metathesis

Polymerization) et la polycondensation classique.

La polymérisation par métathèse des diènes acycliques (ADMET) permet d’obtenir

des polymères de faibles polydispersités avec des doubles liaisons régulièrement

réparties le long des chaînes du polymère.

La polycondensation, elle, permet d’obtenir directement des copolymères de

configuration cis ou trans avec incorporation régulière ou aléatoire des doubles

liaisons.

17

1.6 Méthodologie

1.6.1 Polymérisation par métathèse des diènes acycliques (ADMET)

Dans la science des matériaux, la métathèse des oléfines permet, entre autres, de faire

des réactions de polymérisation par métathèse de diènes acycliques plus connues sous

le nom de ADMET (en anglais : Acyclic Diene Metathesis Polymerization).60 Ces

réactions de polymérisation sont rendues possibles par l’usage d’un certain type de

catalyseurs carbéniques qui peuvent différer par la nature du métal central (titane,

molybdène, tungstène, ruthénium).61 Cependant, un choix approprié du catalyseur est

important pour éviter les réactions secondaires indésirables qui peuvent avoir lieu

entre le catalyseur et les groupements fonctionnels du milieu réactionnel. Ces derniers

peuvent se lier avec le centre actif du métal et ainsi désactiver complètement le

catalyseur.62 Le succès de la polymérisation par métathèse des oléfines repose donc

sur l’usage de catalyseurs qui réagissent préférentiellement avec des oléfines en

présence de groupements fonctionnels hétéroatomiques.

Une étude permettant de suivre la réactivité des catalyseurs à base de titane,

tungstène, molybdène et ruthénium vis-à-vis des oléfines en présence d’autres

groupements fonctionnels a montré que ceux formés de ruthénium sont beaucoup

plus sélectifs aux oléfines qu’aux autres groupements fonctionnels présents dans le

milieu réactionnel.62

18

Tableau 1.2: Réactivité des catalyseurs à base de titane, tungstène, molybdène et

ruthénium vis-à-vis des oléfines en présence de groupements fonctionnels

hétéroatomiques62

Titane Tungstène Molybdène Ruthénium

Acides Acides Acides Oléfines

Ordre de

réactivité

des

oléfines

Alcools, Eau Alcools, Eau Alcools, Eau Acides

Aldéhydes Aldéhydes Aldéhydes Alcools, Eau

Cétones Cétones Oléfines Aldéhydes

Esters, Amides Oléfines Cétones Cétones

Oléfines Esters, Amides Esters, Amides Esters, Amides

De cette étude, dont les résultats sont résumés dans le Tableau 1.2, on conclut que les

catalyseurs au titane, tungstène et molybdène sont plus disposés à réagir avec les

groupements acides, alcools, eau, et aldéhydes qu’avec les oléfines alors que ceux à

base de ruthénium sont plus sélectifs aux alcènes.

Hormis le choix du catalyseur, le choix d’un bon solvant s’impose pour cette

polymérisation. Schulz et al.63 ont indiqué que la réussite de cette polymérisation

dépend de la capacité du solvant à :

- initier le catalyseur ;

- augmenter la réactivité des espèces actives du catalyseur et du substrat ;

- maintenir l’activité du catalyseur pour un temps plus ou moins long.

Ce groupe a effectué la polymérisation par métathèse des diènes acycliques dans

différents solvants (Figure 1.5) en utilisant les catalyseurs de Grubbs deuxième

génération et Hoveyda – Grubbs. L’étude a révélé que les réactions effectuées dans le

dichlorométhane présentaient les masses molaires les plus élevées.

19

Figure 1.5 : Comparaison des masses molaires obtenues par ADMET avec les

catalyseurs de Grubbs deuxième génération et Hoveyda – Grubbs dans différents

solvants63

Dans le cadre du présent projet, deux types de catalyseurs à base de ruthénium ont été

utilisés : le Grubbs deuxième génération (G2) et le Hoveyda-Grubbs (HG) (Schéma

1.8). Ces catalyseurs sont, non seulement plus tolérants aux groupes fonctionnels

présents dans le milieu réactionnel, mais aussi plus actifs et plus stables en présence

d’air et d’humidité.62,64-67 Le dichlorométhane a été sélectionné comme solvant.

Schéma 1.8 : Catalyseurs de Grubbs utilisés pour l’ADMET

20

Pour ce type de polymérisation, le catalyseur réagit avec une oléfine pour la

formation du polymère. Il est donc important de trouver une architecture appropriée

pour le monomère pour que la réaction ait lieu (Schéma 1.9). Ainsi, des groupements

allyliques ont été connectés aux deux bouts d’une macromolécule à base

d’éthersulfones qu’on appellera par la suite, bloc rigide, tel qu’illustré dans le Schéma

1.9.

Schéma 1.9: Polymérisation par métathèse des diènes acycliques (ADMET)

Le mécanisme de polymérisation par métathèse de diènes acycliques est bien connu

et, est composé de cinq (5) étapes principales, tel qu’illustré dans le Schéma 1.10. La

réaction commence par une liaison de coordination entre l’oléfine et le métal central

du catalyseur (1), suivie de la formation d’un intermédiaire métallacyclobutane (2).

Le clivage productif de cet intermédiaire conduit à la formation d’un complexe

alkylidène actif (3) qui peut réagir avec un diène pour former un autre complexe

métallacyclobutane (4). Celui-ci se clive à son tour pour donner le polymère. Le

catalyseur est régénéré et peut réagir de nouveau avec un autre diène ou un polymère

en croissance pour former encore un complexe métallacyclobutane (5) dont le clivage

conduit à la formation d’un nouveau complexe alkylidène avec dégagement de

l’éthylène, et puis la réaction se poursuit.

21

Schéma 1.10 : Mécanisme de polymérisation par métathèse des diènes acycliques

(ADMET)69,70

Les blocs rigides sont synthétisés dans ce projet par substitution nucléophile

aromatique qui reste le procédé approprié pour synthétiser les éthersulfones14 du fait

de sa régiospécificité.68 Ce type de réaction nécessite l'utilisation de solvants polaires

aprotiques tels que le diméthylsulfoxide ou le N,N-diméthylacétamide qui augmentent

l’activité de la base par une solvatation importante du contre-cation.

1.6.2 Polycondensation

La polymérisation par métathèse des diènes acycliques (ADMET) ne permet pas

d’introduire les segments flexibles dans les chaînes du polymère de façon aléatoire.

Elle ne permet pas, non plus, de diminuer la concentration de ces segments flexibles

dans les chaînes du polymère au moment de la polymérisation, ce qui fait qu’on

obtient des copolymères dont la rigidité n’est pas assez importante pour compenser

22

l’effet des segments flexibles sur les températures de transition vitreuse. La

polycondensation permet non seulement, de contourner cet effet mais aussi de

synthétiser directement des copolymères de configuration cis ou trans ayant des

propriétés différentes (solubilité, cristallinité, propriétés thermique) en faisant réagir

respectivement un monomère flexible de configuration cis ou trans avec un bloc

rigide à base d’éthersulfone (Schéma 1.11). On sauve également une étape dans la

synthèse du monomère (bloc rigide), car on n’a pas besoin de connecter les

groupements allyliques en bouts de chaîne.

Le rapport bloc rigide/segment flexible peut donc être contrôlé dans le cas de la

polycondensation, ce qui permet de moduler les températures de transition vitreuse

(Tg) des copolymères résultants. L’utilisation de monomères flexibles de

configuration cis ou trans permet également de contrôler la cristallinité des

copolymères.

Un avantage de la polycondensation vient de la grande variété des monomères

utilisables, ce qui permet d’ajuster les propriétés des polymères selon l’application.

Cependant, il est important d’avoir un mélange équimolaire entre les monomères

pour obtenir de hautes masses. Les indices de polydispersité sont également plus

élevés dans une réaction de polycondensation que dans une ADMET.

Schéma 1.11: Illustration de la polycondensation entre un bloc rigide et un segment

flexible

1.6.3 Caractérisation des polymères

Les copolymères obtenus par ces deux approches sont ensuite caractérisés

principalement par résonance magnétique nucléaire (RMN) et spectroscopie

infrarouge à transformée de Fourier (FTIR) pour l’identification, chromatographie

23

d’exclusion stérique (SEC) pour évaluer les masses molaires, analyse

thermogravimétrique (TGA) pour déterminer les températures de dégradation,

calorimétrie différentielle à balayage (DSC) pour obtenir les températures de

transition vitreuse et de fusion et par diffraction des rayons x pour l’étude de la

cristallinité.

La spectrométrie de masse MALDI-TOF (Matrix-Assisted Laser

Desorption/Ionisation - Time Of Flight, en français : désorption/ionisation laser

assistée par matrice - temps de vol) est utilisée pour montrer que l’incorporation des

segments flexibles dans les chaînes du polymère se fait de manière aléatoire ou s’il y

a création de blocs polymères par réaction préférentielle d’un des monomères au

début de la réaction. Nous allons donner une brève description de cette méthode qui

est de plus en plus utilisée pour caractériser les polymères.

La spectrométrie de masse est une technique d'analyse physico-chimique permettant

de détecter, d'identifier et de quantifier des molécules d’intérêt par mesure de leur

masse. Son principe réside dans la séparation en phase gazeuse de molécules chargées

(ions) en fonction de leur rapport masse/charge (m/z).

Le spectromètre de masse MALDI-TOF est un spectromètre utilisant une source

d’ionisation laser assistée par une matrice et un analyseur à temps de vol. C’est une

technique d'ionisation douce (ionisation sans fragmentation) qui permet l'analyse

de biomolécules (des biopolymères comme les protéines, les peptides et les sucres) et

les grosses molécules organiques (comme les polymères, les dendrimères et

autres macromolécules) sensibles à la chaleur sans se dégrader.

L’échantillon à analyser est dispersé dans une matrice qui permet de faciliter sa

vaporisation et son ionisation. La matrice est une molécule qui a une pression de

vapeur assez grande afin de ne pas s'évaporer sous un certain vide et durant la

préparation de l'échantillon, une faible masse moléculaire pour faciliter la

vaporisation, une forte absorption dans l'ultraviolet, lui permettant d'absorber

https://fr.wikipedia.org/wiki/Ionisation

https://fr.wikipedia.org/wiki/Biomol%C3%A9cule

https://fr.wikipedia.org/wiki/Chimie_organique

24

efficacement et rapidement l'irradiation laser. Elle doit aussi être soluble dans un

solvant approprié aux molécules étudiées.

Pour les PEES, on utilise généralement le dithranol ou bien le trans-2-[3-(4-tert-

butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) comme matrice.71

Un agent cationisant comme des ions Na+ ou Li+ est ajouté au mélange

(échantillon/matrice). L’ensemble est co-cristallisé sur une plaque MALDI par

évaporation du solvant. L'ionisation, qui s’effectue dans la chambre d’ionisation, est

provoquée par irradiation sous vide du dépôt solide par des impulsions laser de

longueur d’onde où la matrice présente une forte absorption. Il en résulte une

désorption puis une désolvatation avec transfert de proton (H+) de la matrice

photoexcitée aux molécules de l’échantillon analysé. L’ionisation des molécules de

l’échantillon se produit principalement par transfert de protons à partir de la matrice

et il se forme l’ion moléculaire [M+H]+. Des molécules sont également ionisées par

l’addition de l’agent cationisant pour former l’ion moléculaire [M+cation]+.

Cependant, il y a controverse sur la formation de ces ions.72 Knochenmuss et al.73

mettent en jeu la réaction ion-molécule dans le nuage formé par la désorption de

l’échantillon et Frankevich et al.74 indiquent que les électrons proviennent non pas de

la matrice photoionisée mais du support métallique de l’échantillon.

Les ions moléculaires générés sont accélérés dans un champ électrique et pénètrent

dans l’analyseur à temps de vol (tube de vol) où ils sont séparés en fonction de leur

temps de vol qui est proportionnel au rapport m/z (m/z = 2U. t2/L2 avec U = tension

appliquée, t = temps de vol, L = longueur du tube de vol).

Plus un ion monochargé sera lourd, c’est-à-dire plus son rapport m/z sera élevé, plus

il va mettre plus de temps pour arriver au détecteur.

Le détecteur transforme le courant ionique en courant électrique permettant d’obtenir

un spectre de masse caractérisant l’échantillon.75-77

La technique MALDI_TOF produit de manière générale des ions moléculaires

monochargés, mais des ions multichargés ([M+nH]n+) peuvent aussi être observés,

selon la matrice utilisée et/ou l'intensité du laser.

25

Schéma 1.12: Principe de fonctionnement d’un spectromètre de masse MALDI-

TOF.72

Les spectres de masse MALDI-TOF peuvent être obtenus en mode linéaire ou

réflectron selon l’équipage de l’appareil.

En mode linéaire, le temps de vol des ions moléculaires est plus court (Figure 1.6) et

la résolution des pics du spectre est plus faible.72 Les ions de même rapport m/z

peuvent arriver au détecteur à des moments différents dû au fait qu’ils n’ont pas la

même énergie cinétique (donc qu’ils ont des vitesses différentes) à l’entrée de

l’analyseur, ce qui a pour conséquence d’élargir les pics du spectre obtenu.

En mode réflectron, le spectromètre MALDI-TOF est équipé d’un réflectron (Figure

1.6), encore appelé miroir électrostatique, qui a pour but de dévier le faisceau ionique

Représentation des

données dans un spectre

de masse

Séparation des ions

produits en fonction du

rapport m/z

Production d’ions en

phase gazeuse

Conversion du courant

ionique en courant

électrique

Chambre

d’ionisation

Analyseur à temps

de vol

Détecteur

Traitement du

signal

26

avec un champ électrique, de regrouper les ions de masse similaire et de les diriger

vers un second tube de vol qui les conduit vers un second détecteur.

Pour des ions ayant le même rapport m/z mais des énergies cinétiques différentes,

l’ion le plus rapide va entrer plus profondément dans le miroir électrostatique. Il va

parcourir alors une plus grande distance et passera plus de temps dans le réflectron

que l’ion le plus lent. Ce phénomène conduit à une arrivée simultanée des ions de

même rapport m/z au niveau du détecteur malgré leur différence de vitesse de départ,

ce qui augmente la résolution des pics des spectres obtenus.

Figure 1.6: Composants basiques d’un spectromètre MALDI-TOF utilisable en mode

linéaire et mode réflectron72

L’étalonnage en masse de l’appareil MALDI s’effectue à l’aide de calibrants dont les

masses molaires encadrent les valeurs de m/z des molécules d’intérêt.

Cette technique est, cependant, limitée par la masse et la volatilité des molécules

analysées et par les limites physiques des détecteurs utilisés.75

Matrice/échantillon

Détecteur en

mode réflectron

Détecteur en

mode linéaire

Réflectron

Ions

Source Laser

27

1.6.4 Post-fonctionnalisation des copolymères

La post-fonctionnalisation a pour but de moduler l’hydrophilicité des copolymères et,

est effectuée en utilisant les réactions thiol-ène clic. La méthode consiste à irradier la

solution par la lumière d’une lampe à rayons ultraviolets (UV) de longueur d’onde

365 nanomètres, nécessaire pour la formation du radical photoinitiateur utilisé dans

ce travail, le 2,2-diméthoxy-2-phénylacetophénone (DMPA). Après échange de

proton avec le radical photoinitiateur, le radical thiol formé réagit avec une double

liaison pour donner le copolymère fonctionnalisé. Les différentes molécules

commerciales utilisées pour la post-fonctionnalisation sont sélectionnées suivant les

groupements fonctionnels hydrophiles qu’ils contiennent. Ainsi des polyéthylènes

glycols (PEG) de faibles et de hautes masses molaires sont utilisés (voir chapitre 4).

Des molécules hydrophobes sont également utilisées dans ce travail à titre de

comparaison.

1.6.5 Mesures d’angle de contact

Après la post-fonctionnalisation, des mesures d’angles de contact sont effectuées pour

évaluer l’hydrophilicité des copolymères.

La mesure d'angle de contact rend compte de l'aptitude d'un liquide à s'étaler sur une

surface par mouillabilité.

La méthode consiste à mesurer l'angle de la tangente du profile d'une goutte avec la

surface du substrat sur laquelle elle est déposée.

En utilisant l'eau comme liquide de mesure d'angle de contact, on peut déduire le

caractère hydrophobe (grand angle, faible énergie de surface, faible mouillabilité) ou

hydrophile (petit angle, grande énergie de surface, bonne mouillabilité) de la surface

(Figure 1.7).

28

Figure 1.7: Mesure de l’angle de contact

(adapté à partir de University of Western Ontario,

http://www.eng.uwo.ca/zeolite/Goniometer.htm, consulté le 17 janvier 2016)

En pratique, une goutte de liquide, en général de l’eau ultra-pure, est déposée à l’aide

d’une seringue sur une surface de l’échantillon à analyser éclairée par une source

lumineuse et à l’aide d’une caméra, tout étant contrôlé par ordinateur (Figure 1.8).

http://www.eng.uwo.ca/zeolite/Goniometer.htm

29

Figure 1.8: Principe de mesure de l’angle de contact

(adapté à partir de http://www.biophyresearch.com/technique-analyse/angles-de-

contact/ consulté le 17 janvier 2016)

En mesurant l’hystérèse (différence des angles d’avancement et de retrait de la

goutte), on obtient des renseignements sur l’homogénéité de la surface.

En faisant une série de mesures d’angles de contact avec différents liquides de

tensions superficielles connues (eau, glycérol éthylène glycol, diiodométhane, etc.),

on peut accéder à l'énergie libre de la surface, tout en discriminant les composantes

polaires ou apolaires de cette énergie en utilisant le modèle de Good Van Oss ou celui

de Owens Wendt.78 Ces modèles ne seront pas développés dans ce document car ils

sont liés à la détermination des tensions superficielles des liquides ou solides, ce qui

n’est pas lié à notre objectif dans ce projet.

http://www.biophyresearch.com/technique-analyse/angles-de-contact/

http://www.biophyresearch.com/technique-analyse/angles-de-contact/

30

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contact/ , Consulté le 17 janvier 2016.

34

Chapitre 2: Crystallization control of

etherethersulfone copolymers by regular insertion

of an allyl functionality

Adrien Faye, Mikaël Leduc and Josée Brisson*, Polym. Chem., 2014, 5, 2548.

*Département de chimie and Centre de recherche sur les matériaux avancés

(CERMA),

Faculté des sciences et de génie, Université Laval,

1045 Avenue de la Médecine, Québec, Canada G1V 0A6.

E-mail: [email protected];

Fax: +1 418 656 7916;

Tel: +1 418 656 3536

mailto:[email protected]

35

Résumé

L’ADMET et la polycondensation par substitution nucléophile ont été utilisées pour

synthétiser des copolymères alternés à base de PEES. La polymérisation par ADMET

a conduit à des copolymères où un segment flexible (but-2-ène) est alterné avec des

blocs rigides étheréthersulfones (EES). Les copolymères obtenus sont de

configuration majoritairement trans avec plus de 94 à 98% de sélectivité, ont des Mw

qui atteignent 13 600 g mol-1 et sont de faibles polydispersités (Ip = 1,1 à 1,4).

D'autre part, la polycondensation a permis d'incorporer des segments flexibles de

configuration cis ou trans dépendamment du monomère utilisé. Des masses

moléculaires de même ordre grandeur ont été obtenues mais, comme prévu, avec des

Ip plus élevés (jusqu'à 2,3). La caractérisation des copolymères par DSC et par

diffraction des rayons X a permis de montrer que l'incorporation du segment de

configuration cis inhibe complètement la cristallisation, alors que l’isomère trans la

favorise. La cristallinité disparaît après la fusion, mais elle peut être restaurée en

recristallisant par un solvant approprié. La forme cristalline observée change avec la

longueur du bloc EES. Pour une unité de répétition de petite longueur (contenant un

bloc EES de 4 noyaux aromatiques), le segment flexible est incorporé dans l’unité de

répétition de la phase cristalline, tandis que, lorsque le bloc EES est porté à huit

noyaux aromatiques, le segment flexible est exclu de la phase cristalline. La

possibilité d’une post-fonctionnalisation du groupement flexible a été démontrée par

une réaction d’hydrogénation. Le copolymère résultant adopte une forme cristalline

différente pour le bloc de 4 noyaux aromatiques, mais, pour le bloc à 8 noyaux

aromatiques, la forme cristalline reste la même, confirmant ainsi que l'incorporation

du segment flexible dans l'unité de répétition cristallographique dépend de la

longueur du bloc.

36

Abstract

Acyclic diene metathesis (ADMET) polymerization and nucleophilic aromatic

substitution polycondensation are used to synthesize alternating copolymers based on

polyetherethersulfone (PEES) blocks. ADMET results in incorporation of trans-allyl

groups with more than 94 to 98% selectivity. The resulting polymers have a Mw of up

to 13 600 g mol-1 and low dispersity (Đ = 1.1 to 1.4). Polycondensation, on the other

hand, allows incorporation of either cis- or trans-allyl groups depending on the

starting monomers. Molecular weights in the same range are obtained, but with much

larger dispersity (up to 2.3), as expected. Characterization by differential scanning

calorimetry and wide angle X-ray diffraction shows that incorporation of the cis

group completely suppresses crystallization, whereas that of the trans group results in

semi-crystalline polymers. Crystallinity is lost post-melting, but can be restored using

appropriate solvent treatments. The crystal form changes with the length of the

etherethersulfone (EES) group indicating that, when the repeat unit is small

(containing a 4-ring etherethersulfone (EES) block), the allyl function is incorporated

into the crystallographic repeat, whereas when the EES segment increases to eight

rings, the allyl group is excluded from the crystal phase. Post-functionalization of the

allyl group is demonstrated by using hydrogenation. The resulting polymer adopts a

different crystal form for the 4-ring block, but the same crystal form for the 8-ring

block, confirming the dependence on the block length for incorporation into the

crystallographic repeat unit.

37

2.1 Introduction

Poly(ethersulfones) (PES) and poly(etherethersulfones) (PEES) show outstanding

thermal, chemical and radiative performances and are found in many applications.1

Modulation of properties such as hydrophobicity2, amphiphilicity3, glass transition

temperature4 or morphology via self-organization5 through random or block

copolymerization has been proposed to improve their properties and tailor these to

specific applications.

Little attention has been given to one specific morphological feature, which markedly

influences the resulting polymer properties: crystallinity. This is due to the fact that,

in spite of their regular structure, polyethersulfones are generally considered as being

amorphous. Although they are often slightly crystalline as synthesized, melting

during processing destroys this crystallinity, and annealing does not allow us to

restore it.

This is an unusual feature for such a regular homopolymer, partly attributed to an

abnormally narrow interval between Tg and Tm.6 However, long-term crystallization

occurs, and as the initially amorphous polymer slowly crystallizes, voids and cracks

may appear due to morphology reorganizations, thereby contributing to premature

failure.

Control of semi-rigid polymer crystallization through the introduction of regularly

inserted spacers has been the object of attention in our group. Previous work has

shown that introduction of flexible aliphatic chains of six to eight methylene units did

not decrease the crystallinity of poly(para-phenylene terephthalamides)7 (PPTA) and

poly(etheretherketones)8 (PEEK), and that single crystals could be obtained, the

flexible spacers being segregated at the crystal surface and acting as fold sites. A

crystallizable rigid block of one and a half repeat unit was found sufficient for the

resulting crystal structure to be the same as that of the parent rigid homopolymer in

PPTA-based copolymers7, in agreement with the previously proposed value of one

repeat unit9. Below this minimum requirement, the crystallographic repeat unit will

38

correspond to a combination of units forming a new homopolymer with a crystal

structure different from that of parent units.

In this work, two aims were sought: firstly, synthesis of PEES containing post-

functionalizable groups was targeted. These will allow fine-tuning of various

properties of the resulting polymers while minimizing synthetic efforts. Various

applications may in this way be targeted, but in the present work, only the proof of

concept will be made. Secondly, as a demonstration of the ability to modify polymer

properties through incorporation of an allyl spacer, modulation of the PEES ability to

crystallize was selected. The cis and trans isomers of the allyl group offer the

possibility of investigating whether the group promotes chain folding, either by pre-

orientation of chains in an antiparallel fashion or alternatively by favoring regular

alignment along the chain direction. In this respect, such a system can bring a

different light on the possible mechanism of polymer crystallization.

In the present work, two different synthesis approaches were used: acyclic diene

metathesis polymerization or ADMET for its low polydispersities and nucleophilic

aromatic substitution polycondensation, which allowed synthesis of cis- or trans-allyl

copolymers by changing the spacer inserted between rigid blocks. A rigid

ethersulfone block of four aromatic rings was first studied, and preliminary work on

eight-ring blocks will also be reported. In both cases, results are discussed in terms of

the ability of the allyl group to either inhibit or promote crystallization, the effect of

dispersity and the number of repeat units in the regular block. A few post-synthesis

modifications were made, to illustrate the concept of property changes through post-

functionalization.

39

2.2 Experimental section

2.2.1 Instrumentation

Nuclear magnetic resonance (NMR) spectroscopy measurements were performed in

CDCl3 or dimethyl sulfoxide-d6 solutions on a Bruker AMX 400 MHz at room

temperature.

Size exclusion chromatography (SEC) was carried out on a system composed of a

515 HPLC pump, two Agilent PL-Gel Mixed B-LS columns and a UV detector

Model 441 coupled to a LASER Dawn DSP photometer. Monodisperse poly(styrene)

standards were used for calibration and chloroform (CHCl3) as eluent at a flow rate of

1.0 mL min-1. The sample concentration was 0.175 mg mL-1. Chromatograms were

analyzed with the ASTRA software version 4.70.07.

Thermogravimetric analyses (TGA) were performed on a Mettler

TGA/SDTA851e/SF/1100 C equipped with an MT1 balance, under a nitrogen

atmosphere.

Glass transition Tg and melting temperatures Tm were determined as the midpoint of

the transitions using a differential scanning calorimeter (DSC) Mettler DSC823e

apparatus under a nitrogen atmosphere. The scan rate was 10 °C min-1 and liquid

nitrogen was used for cooling purposes. In some cases, cooling rates down to 1 °C

min-1 were used, and the selected samples were also annealed between Tg and Tm1 for

15 minutes to 24 hours. In all cases, the STARe software version 9.30 was used for

data acquisition and processing. The degree of crystallinity was estimated by DSC

using the following equation:

χDSC =∆𝐻𝑚

∆𝐻𝑚° x 100 (1)

40

where ∆𝐻𝑚 is the melt enthalpy, determined as the area under the melt endotherm,

and ∆𝐻𝑚° is the melt enthalpy of a completely crystalline sample. For the polymers

synthesized in this work, as the value of this constant was not known, as a first

approximation the value of 130 kJ g-1 for a polymer with a similar chemical structure,

poly(etheretherketone), was used.10

Crystallinity was studied by wide angle X-ray scattering (WAXS), using a Bruker

diffractometer equipped with a Kristalloflex 760 generator, a 3-circle goniometer and

a Hi-Star area detector. The generator produced graphite monochromatized copper

radiation (Cu Kα = 1.54178 Ǻ) at 40 kV and 40 mA. Diffraction diagrams were

recorded in the transmission mode. Crystallinity χx−ray was estimated from the

following equation:

χ𝑥−𝑟𝑎𝑦 =𝐼𝑐𝑟𝑦𝑠𝑡

𝐼𝑡𝑜𝑡𝑎𝑙 × 100 (2)

where Itotal is the total integrated intensity of the diffraction curve and Icryst is the

intensity of the crystalline peaks, determined by integrating the diffraction curve after

subtraction of the amorphous halo of a representative amorphous polymer.

Molecular models were built using HyperChem Pro 6.0 (Hypercube, Inc), energies

minimized using the block diagonal Newton–Raphson method until a root mean

square gradient of 0.1 kcal Ǻ-1 mol-1 was reached, and the force field used was MM+.

2.2.2 Materials

Bis(4-fluorophenyl) sulfone (99%), 4-methoxyphenol (99%), allyl iodide (98%),

boron tribromide (BBr3, 99.9%), N,N-dimethylacetamide (DMAc, 99+%), N-methyl

pyrrolidone (NMP), Grubbs 2nd generation catalyst (G2), Hoveyda–Grubbs catalyst

(HG) and palladium 10 wt% on activated carbon were all supplied by Sigma Aldrich

and used without any purification. Anhydrous acetone (C3H6O, 99.7%),

tetrahydrofuran (THF) and dimethylsulfoxide (DMSO) were purchased from Fisher

41

Scientific and used directly. Dichloromethane (CH2Cl2, Fisher Scientific, 99.9%) was

dried by stirring with CaH2 and then distilled prior to use. Anhydrous potassium

carbonate (K2CO3, 99%) was supplied by EMD.

2.2.3 Synthesis of monomers

2.2.3.1 Synthesis of 4,4’-bis(4-methoxyphenoxy) diphenyl sulfone (MPDS)

(Scheme 2.1a)

A round bottom flask (25 mL) was charged with 10.002 g (39.34 mmol) of bis(4-

fluorophenyl) sulfone, 9.767 g (78.68 mmol) of 4-methoxyphenol and 11.96 g (86.54

mmol) of potassium carbonate. To this mixture was added 40 mL of DMAc and the

resulting solution was stirred and heated to 180 °C over the course of 4 hours using

an oil bath, as shown in Scheme 2.1. The reaction mixture was allowed to cool and

precipitated into a 1 M HCl aqueous solution, filtered and washed with a saturated

NaCl aqueous solution three times to remove DMAc and potassium carbonate5. The

white solid was dried in vacuo at 60 °C for 8 hours (15.2 g, 32.8 mmol, 83%).

1H-NMR 400 MHz (CDCl3, r.t.) : δ 7.82 (d, 4H, 3J = 8.94 Hz, 4J = 2.50 Hz), 7.26

(CHCl3), 6.97 (d, 4H, 3J = 8.94 Hz, 4J = 2.50 Hz), 6.94 (d, 4H, 3J = 8.94 Hz, 4J =

2.50 Hz), 6.90 (d, 4H, 3J = 8.94 Hz, 4J = 2.50 Hz), 3.82 (s, 6H), 1.56 (H2O) ppm.

13C-NMR (CDCl3, r.t.) : δ 162.7, 156.8, 147.9, 134.9, 129.5, 121.7, 116.8, 115.1, 55.5

ppm.

42

a)

b)

Scheme 2.1: Synthesis of monomer precursors: (a) APDS (4-ring) precursor and (b)

HPSPPDS (8-ring) precursor

2.2.3.2 Synthesis of 4,4’-Bis(4-hydroxyphenoxy) diphenyl sulfone (HPDS)

(Scheme 2.1a)

As adapted from by Hayakawa et al.5, a round bottom flask (25 mL) containing a

magnetic stirrer was charged with 8.001 g (17.30 mmol) of 4,40-bis(4-

methoxyphenoxy) diphenyl sulfone (MPDS). To this mixture was added 20 mL of

dichloromethane, and the resulting solution was treated dropwise with 13.1 mL (138

mmol) of boron tribromide under completely dry conditions and under nitrogen. The

solution was stirred for 1 hour at 0 °C, an additional 5 hours at room temperature and

43

then poured into cold water (500 mL). The precipitate was filtered and recrystallized

from dichloromethane to purify it before being dried in vacuo at 60 °C for 8 hours

(7.513 g, 17.29 mmol, 99.96%).

1H-NMR 400 MHz ((CD3)2SO, r.t.): δ 9.52 (s, 2H), 7.84 (d, 4H, 3J = 8.94 Hz, 4J =

2.14 Hz), 6.99 (d, 4H, 3J = 8.94 Hz, 4J = 2.14 Hz), 6.94 (d, 4H, 3J = 8.94 Hz, 4J =

2.14 Hz), 6.80 (d, 4H, 3J = 8.94 Hz, 4J = 2.14 Hz), 5.76 (CH2Cl2), 3.34 (H2O), 2.50

(DMSO) ppm.

13C-NMR (CDCl3, r.t.): δ 163.0, 155.2, 146.4, 134.9, 130.1, 122.3, 117.1, 116.9 ppm.

2.2.3.3 Synthesis of 4,4’-bis(4-allyloxyphenoxy) diphenyl sulfone (APDS)

(Scheme 2.1a)

Anhydrous K2CO3 was added to a solution of 4,4’-bis(4-hydroxyphenoxy) diphenyl

sulfone (HPDS) (4.518 g, 10.40 mmol) and 18-crown-6 (0.566 g, 2.142 mmol) in

acetone (20 mL). The reaction mixture was stirred at room temperature for 2 hours

under a nitrogen atmosphere, treated with allyl iodide (2.0 mL, 21 mmol) and heated

at 60 °C for 6 hours using an oil bath. The reaction mixture was cooled to room

temperature, quenched with aqueous NaCl, and concentrated under reduced pressure.

The crude product was diluted with dichloromethane and extracted with H2O. The

organic layer was dried over MgSO4 and filtered, and the solvent was evaporated.

The white solid was filtered and dried in vacuo at 60 °C for 8 hours (2.9 g, 5.6 mmol,

54%).

1H-NMR 400 MHz (CDCl3, r.t.): δ 7.82 (dd, 4H, J = 9.02 Hz, J = 2.00 Hz), 7.26

(CHCl3), 6.96 (dd, 4H, 3J = 9.27 Hz, 4J = 2.50 Hz), 6.94 (dd, 4H, 3J = 9.02 Hz, 4J =

2.00 Hz), 6.91 (dd, 4H, 3J = 9.27 Hz, 4J = 2.50 Hz), 6.01 (m, 2H, 3Jtrans = 17.28 Hz,

3Jcis = 10.51 Hz, 3J = 5.30 Hz), 5.40 (ddd, 2H, 3Jtrans = 17.28 Hz, 4J = 3.15 Hz, 2J =

1.60 Hz), 5.29 (ddd, 2H, 3Jcis = 10.51 Hz, 4J = 2.82 Hz, 2J = 1.39 Hz), 4.53 (dt, 4H, 3J

= 5.30 Hz, 4J = 3.05 Hz, 4J = 1.55 Hz), 1.56 (H2O) ppm.

44

13C-NMR (CDCl3, r.t.): δ 162.7, 155.9, 148.1, 135.0, 133.0, 129.6, 121.7, 117.9,

116.9, 116.0, 69.2 ppm.

2.2.3.4 Synthesis of 4-fluoro-4’-hydroxy diphenyl sulfone (FHDS) (Scheme 2.1b)

A round bottom flask (25 mL) containing a magnetic stirrer was charged with 15.001

g (59.000 mmol) of bis(4-fluorophenyl sulfone) (FPS) and 2 eq. of aqueous KOH 7.0

M (16.9 mL, 118 mmol). To this mixture was added 20 mL of DMSO and the

resulting solution was heated to 75 °C for 20 hours using an oil bath, as shown in

Scheme 1b. The reaction mixture was allowed to cool, poured dropwise into 50 mL

of water and washed 3 times with 100 mL of toluene. The aqueous phase was

recovered and then acidified with 100 mL of HCl 8M. The solution was stirred for 5

minutes and then filtered. The white product obtained (13.1 g, 51.9 mmol, 88%) was

dried at 60 °C under vacuum for 8 hours.

1H-NMR 400 MHz ((CD3)2SO, r.t.): δ 10.65 (s, 1H), 7.93 (d, 1H, 3J = 8.85 Hz, 4J ¼

2.04 Hz), 7.75 (d, 1H, 3J = 8.85 Hz, 4J = 2.04 Hz), 7.40 (d, 1H, 3J = 8.85 Hz, 4J =

2.04 Hz), 6.90 (d, 1H, 3J = 8.85 Hz, 4J = 2.04 Hz), 3.33 (H2O), 2.50 (DMSO) ppm.

13C-NMR 400 MHz ((CD3)2SO, r.t.): δ 165.6, 163.1, 138.5, 130.4, 129.9, 129.8,

129.7, 129.2, 116.0 ppm.

2.2.3.5 Synthesis of 4-fluoro-4’-methoxy diphenyl sulfone (FMDS) (Scheme 2.1b)

A round bottom flask (25 mL) containing a magnetic stirrer was charged with 3.279 g

(13.00 mmol) of 4-fluoro-40-hydroxy diphenyl sulfone (FHDS), 1.845 g (13.00

mmol) of iodomethane and 2.156 g (15.60 mmol) of potassium carbonate. To this

mixture was added 20 mL of DMAc and the resulting solution was heated to 75 °C

for 20 hours using an oil bath (Scheme 1b). The reaction mixture was allowed to cool

and precipitated dropwise into 150 mL of aqueous KOH 1 M. The solution was

stirred for 5 minutes and then filtered. The white product obtained was dissolved in

dichloromethane and filtered, and the solvent was evaporated under reduced pressure.

45

The product was dried at 60 °C under vacuum for 8 hours (3.400 g, 12.77 mmol,

98%).

1H-NMR 400 MHz (CDCl3, r.t.): δ 7.90 (d, 1H, 3J = 8.89 Hz, 4J = 2.13 Hz), 7.84 (d,

1H, 3J = 8.89 Hz, 4J = 2.13 Hz), 7.26 (CHCl3), 7.12 (d, 1H, 3J = 8.89 Hz, 4J = 2.13

Hz), 6.95 (d, 1H, 3J = 8.89 Hz, 4J = 2.13 Hz), 3.83 (s, 3H), 1.56 (H2O) ppm.

13C-NMR 400 MHz (CDCl3, r.t.): δ 166.3, 163.8, 138.3, 132.8, 129.9, 129.7, 116.4,

116.2, 114.5, 55.58 ppm.

2.2.3.6 Synthesis of 4,4’-bis(4-(4-(4-methoxyphenylsulfonyl)

phenoxy)pentoxy)diphenylsulfone (MPSPPDS) (Scheme 2.1b)


(1.84 mmol) of 4,4’-bis(4-hydroxyphenoxy) diphenyl sulfone (MPDS), 0.980 g (3.68

mmol) of 4-fluoro-4’-methoxy diphenyl sulfone (FMDS) and 0.560 g (4.05 mmol) of

potassium carbonate. To this mixture was added 30 mL of DMAc and the resulting

solution was heated to 180 °C over the course of 20 hours using an oil bath. The

reaction mixture was allowed to cool and precipitated into a 1 M aqueous HCl

solution, filtered and washed with a saturated NaCl aqueous solution three times to

remove DMAc and potassium carbonate. The white solid was dried in vacuo at 60 °C

for 8 hours (1.62 g, 1.75 mmol, 95%).

1H-NMR 400 MHz (CDCl3, r.t.): δ 7.87 (d, 4H, 3J = 8.80 Hz), 7.85 (d, 4H, 3J = 8.80

Hz), 7.26 (CHCl3), 7.05 (s, 8H), 7.01 (d, 4H, 3J = 8.80 Hz), 7.00 (d, 4H, 3J = 8.80

Hz), 6.95 (d, 4H, 3J = 8.80 Hz), 3.84 (s, 6H) ppm.

13C-NMR 400 MHz (CDCl3, r.t.): δ 163.2, 161.7, 161.4, 151.8, 151.6, 136.2, 135.6,

133.3, 129.7, 129.6, 121.9, 121.8, 117.5, 114.4, 55.58 ppm.

46

2.2.3.7 Synthesis of 4,4’-bis(4-(4-(4-hydroxyphenylsulfonyl)phenoxy)phenoxy)

diphenyl sulfone (HPSPPDS) (Scheme 2.1b)


(3.200 mmol) of 4,4’-bis(4-(4-(4-methoxyphenylsulfonyl)phenoxy)phenoxy)

diphenyl sulfone (MPSPPDS). To this mixture was added 20 mL of dichloromethane

and the resulting solution was treated dropwise with 3.9 mL (42 mmol) of boron

tribromide under the same conditions (synthesis and subsequent workup) as described

for HPDS (2.25 g, 2.50 mmol, 78%).

1H-NMR 400 MHz ((CD3)2SO, r.t.): δ 10.6 (s, 2H), 7.91 (d, 4H, 3J = 8.89 Hz), 7.86

(d, 4H, 3J = 8.89 Hz), 7.73 (d, 4H, 3J = 8.89 Hz), 7.20 (s, 8H), 7.12 (d, 4H, 3J = 8.89

Hz), 7.10 (d, 4H, 3J = 8.89 Hz), 6.89 (d, 4H, 3J = 8.89 Hz), 3.33 (H2O), 2.50 (DMSO)

ppm; 13C-NMR 400 MHz ((CD3)2SO, r.t.): δ 161.9, 161.5, 161.1, 151.4, 151.2, 136.1,

135.2, 131.1, 129.8, 129.7, 129.5, 122.3, 122.2, 117.7, 116.1 ppm.

2.2.4 Copolymer synthesis

2.2.4.1 ADMET polymerization of poly(allyl-co-etherethersulfone) (PA-4EES)

(Scheme 2.2a)

The APDS monomer (0.500 g, 0.971 mmol) was dissolved in dichloromethane in a

two-neck flask. The catalyst (G2 or HG, 1- 6.0 mol %) was then added and the

reaction mixture was stirred and heated at 40 °C using an oil bath under a continuous,

low nitrogen flow for one day. Subsequently, ethyl vinyl ether (0.4 mL) was added to

quench the reaction. The obtained product was dissolved in dichloromethane and

precipitated by slowly dropping the solution into cold methanol, filtering off the

solvent and washing the powder with acetone. To remove ruthenium, the polymer

was dissolved again in dichloromethane and then washed three times with 100 mL of

a 0.224 M aqueous solution of sodium diethyldithiocarbamate trihydrate. The product

was finally dried in vacuo at 60 °C overnight. The resulting polymers are designated

47

PA-4EES, where A stands for the allyl group polymerized during the ADMET

reaction, and 4 corresponds to the number of rings in the rigid ethersulfone monomer.

2.2.4.2 Polycondensation of PTA-4EES, PTCA-4EES, PTA-8EES and PCA-

8EES copolymers (Schemes 2.2b and 2.2c)


(8.800 mmol) of anhydrous K2CO3, 1.738 g (4.000 mmol) of the 4-ring monomer

HPDS or 3.596 g (4.000 mmol) of the 8-ring monomer HPSPPDS and 0.500 g (4.000

mmol) of either (Z)-1,4-dichlorobut-2-ene (Z-DCB) or (E)-1,4-dichlorobut-2-ene (E-

DCB). To this mixture was added 10 mL of DMAc and the resulting solution was

heated between 70 °C and 120 °C for one to two days using an oil bath. The reaction

mixture was allowed to cool and precipitated into a 1 M HCl aqueous solution. The

polymer was filtered and dried, redissolved in DMAc, and again precipitated to

ensure salt removal. The resulting polymers are abbreviated PTA-xEES for the E-

DCB synthesis with an x-ring monomer and PCA-xEES for the Z-DCB synthesis.

2.2.4.3 Polycondensation of the PAE-4EES copolymer (Scheme 2.2d)


(2.000 mmol) of 4,4’-bis(4-hydroxyphenoxy) diphenyl sulfone (MPDS), 0.030 g

(0.093 mmol) of tetrabutylammonium bromide (TBAB) and 6mL of NaOH 1 M. The

mixture was stirred until everything was dissolved. To this solution was added 0.306

g (2.000 mmol) of fumaryl chloride, and the mixture was stirred rigorously at room

temperature for 4 hours. The supernatant aqueous layer was decanted and the mixture

was then poured into hot water (200 mL) containing a few drops of concentrated

hydrochloric acid. The crude product (0.850 g, 98%) was collected by filtration,

washed with refluxing methanol, and dried at 80 °C under vacuum overnight.

2.2.4.4 Hydrogenation to obtain PAH-4EES and PAH-8EES

In a solution of PTA-xEES (0.240 g) in dichloromethane (20 mL) was added 10 wt%

palladium on activated carbon (0.080 g) while stirring at ambient temperature. The

48

mixture was purged with hydrogen to replace the air in the flask and then stirred

under a hydrogen atmosphere for 3 hours. The palladium activated carbon was

filtered off, and the solvent was removed under reduced pressure to give the

hydrogenated polymer with a 99% yield. The resulting polymers are abbreviated

PAH-xEES, where H stands for the hydrogenation of the allyl group. The same

abbreviation is used for polymers prepared by using the ADMET monomers, the cis-

containing or the trans-containing monomers, as these will yield the same polymer,

the only difference being the average molecular weights and polydispersities, which

remain, within experimental error, the same as the starting polymer.

2.2.4.5 Halogenation to obtain PACl-4EES and PABr-4EES


of PCA-4EES in dichloromethane (20 mL). The mixture was purged with argon and

then stirred under a chlorine atmosphere for 3 hours. The solvent was removed under

reduced pressure to give the chlorinated polymer with a 99% yield. The resulting

polymer is abbreviated PACl-4EES, where Cl stands for the chlorine of the allyl

group. A round bottom flask (25 mL) containing a magnetic stirrer was charged with

0.600 g of PCA-4EES in dichloromethane (15 mL). To this solution was added

dropwise, under vigorous stirring, bromine (0.036 mL, 0.815 mmol) in 2 mL of

CH2Cl2, as adapted from ref. 11. The mixture was allowed to react for 2 hours and

then poured into water. The precipitated product was filtered and washed with ether.

The brominated polymer, PABr-4EES, was obtained with a yield of 99.5%.

2.2.5 Recrystallization of copolymers.

Solvent recrystallisation was performed by dissolving 5 mg of a polymer in 5 mL of a

solvent or solvent mixture, and the solution was poured into a small Petri dish and

covered. For low boiling-point solvents (THF, CH2Cl2), samples were placed at 4 °C

until evaporation occurred. For samples with higher boiling points, evaporation was

performed at room temperature.

49

2.2.6 Results and discussion

2.2.6.1 Synthesis of polymers

a)

c)

b)

d)

Scheme 2.2: Polymerization reactions: (a) acyclic diene metathesis polymerization

(ADMET) of the APDS monomer, (b) polycondensation of HPDS with (Z) and (E)-1,4-

dichlorobut-2-ene, (c) polycondensation of HPSPPDS with (Z) and (E)-1,4-dichlorobut-2-

ene and (d) polycondensation with fumaryl chloride to insert ester linkages.

50

2.2.6.1.1 PA-4EES copolymer obtained by ADMET polymerization

ADMET was used to polymerize a diallyl-terminated 4-ring macromonomer

obtained, as depicted in Schemes 2.1 and 2.2. The 4-ring block corresponds to an

etherethersulfoneether moiety, or EESE, but by analogy with the 8-ring monomer, it

was chosen to use the EES abbreviation for this polymer, this being the sequence

common to both copolymers. The resulting copolymers are film-forming, but film

brittleness was an indicator of low molecular weight. This was confirmed by NMR

spectroscopy and SEC, as reported in Table 2.1. SEC determination of molecular

weight is relatively straightforward, although the use of poly(styrene) standards can

induce a systematic error on molecular weights. NMR was therefore also used to

quantify molecular weights. Representative NMR spectra are presented in Figure 2.1.

Three small-intensity signals appearing between 4.0 and 6.3 ppm are related to

terminal allyl groups, and decrease in intensity until they disappear into the

background noise with increasing molecular weight. To better visualize the

attribution of these small-intensity peaks, in Figure 2.1b is reported a close-up view

of this spectral region, along with that of an allylated monomer. Protons appearing at

the chain end are denoted by ‘EG’ for the end-group, whether these appear as the

polymer end-group or at the terminal position of the monomer. Peak fEG is a multiplet

in the monomer and the copolymer, whereas peak f is a singlet next to this multiplet.

A very small intensity peak is also observable for the f protons of the cis fraction of

the trans copolymer. Likewise, the e region presents a doublet for the end-groups and

a singlet for hydrogen atoms in the main chain, and a small ‘cis’ peak is also

observed. Spectra were used to calculate number-average molecular weights Mn, as

reported in Table 2.1 (see Scheme A.2.1 for details on Mn calculation), along with

values obtained by SEC. As shown by SEC and as expected, ADMET polymers have

low dispersity.

Molecular weights of 2000 g mol-1 were first obtained. In order to increase the

molecular weight, the amount and the nature of the catalyst, reaction temperature and

reaction time were varied12, but the highest molecular weight achieved was a

51

relatively low value of Mw of 8700 g mol-1 for 6% catalyst at 40 °C for 24 hours

using the Hoveyda–Grubbs catalyst. It is proposed in the literature that molecular

weight can be limited, for this type of polymer due to a coordination bond occurring

between the active center of the catalyst, i.e. ruthenium, and the sulfone group13 or

the ether oxygen during the formation of a metallacyclobutane intermediate,14 thus

disabling the catalyst. This phenomenon has been termed the “negative neighboring

group effect”.15 Tindall et al.14 proposed that the optimum conditions for ADMET

chemistry occur by positioning the functional group at least two methylene units

distant from the metathesizing olefin within the monomer unit. To add a methylene

group between the allyl double bond and the ether oxygen was considered, but as this

would probably decrease the glass transition temperature and degradation temperature

of the resulting polymer, this was not pursued.

Polycondensation yielded slightly higher molecular weights with the cis-monomer,

which were found to be optimal for a reaction temperature of 120 °C, as reported in

Table 2.1. For a reaction temperature up to 150 °C, the molecular weight was

relatively low and no conversion of cis to trans allyl or trans to cis could be detected.

The use of higher temperatures resulted in higher molecular weights especially of the

cis-allyl copolymers. Nevertheless, the low reactivity of the hydroxyl group and high

number of termination reactions limited the obtained molar weight.

A second factor that may have contributed to obtaining low molecular weights is

crystallinity. Crystalline polymers tend to be less soluble than their amorphous

counterparts, and as the polymer crystallizes during polymerization, precipitation can

occur, and chain growth then stops, which leads to low molecular weights16. This

would also explain why temperature has a much more marked effect for the cis-allyl

copolymers than for the more crystalline trans-allyl copolymers.

In order to further improve molecular weights, an additional reaction was performed

using an acid chloride terminated allyl spacer instead of a chloride terminated spacer

in order to replace the ether linkage between the EES block and the allyl spacer by an

ester linkage, as shown in Scheme 2.2d. Due to the higher reactivity of this group,

52

reactions could be performed at room temperature, and higher molecular weights

were achieved, as reported in Table 2.1. This polymer is a better candidate for

eventual applications, but exhibits a lower solubility and a much higher

polydispersity, thus making the ether-linked copolymers more interesting subjects for

fundamental studies on crystallization.

2.2.6.1.2 PTA-xEES and PCA-xEES polymers obtained by polycondensation

To know whether the polymer synthesized by ADMET was in a cis or trans

configuration, FTIR spectroscopy is normally used. In the present case, overlap of

ethersulfone vibration bands made such an attribution less straightforward. Therefore,

it was decided to rely on NMR peak positions of allyl protons to determine this

configuration. To have representative NMR spectra with which comparisons could be

made, polycondensation reactions were performed to synthesize copolymers having

the same chemical structure but with either cis or trans-allyl bonds, as shown in

Scheme 2.2b. This approach further has the advantage of yielding the desired allyl

conformation by choosing the right monomer, but does increase the resulting

dispersity. Molecular weights and polydispersities of these copolymers were

determined by SEC and reported in Table 2.1. The obtained copolymers are in the

same range of molecular weights as those obtained by ADMET, but have much larger

Đ values, as expected.

NMR peak positions for the cis- and trans-allyl isomers are different, allowing easy

determination of isomers present, as reported in Table 2.2. In the trans copolymer

spectrum, a small peak, which represents 10% of the total signal, is present at the

position of the cis isomer. This cis isomer is due to the presence of 10% cis form in

the initial E-DCB monomer (see Figure A.2.4b of the Annexes), purification of the

trans isomer being extremely difficult. This small portion therefore remains in the

polymer.

Comparison of peak positions of PTA-4EES, PCA-4EES and PA-4EES polymers is

reported in Table 2.2, and shows a match between the ADMET polymer, abbreviated

53

PA-4EES, and the trans isomer (PTA-4EES). Inspection of the NMR spectra in

Figure 2.1 shows that, in the ADMET polymer, from 1 to 6% of the cis form is

present, which is less than that in the polycondensation polymer, for which up to 10%

cis isomer was present due to their presence in the starting monomer. A very high

stereoselectivity is therefore achieved with both the Grubbs 2nd generation and the

Hoveyda–Grubbs catalysts for this polymer, along with a low dispersity, and with

molecular weights comparable to those of step-growth polycondensation, although

modest.

Polymers were synthesized using two ethersulfone blocks: the 4-ring block in

polymers abbreviated PTA-4EES and PCA-4EES but which, as mentioned above,

have a EESE block, and the 8-ring block in PTA-8EES and PCA-8EES, which have a

ESEESEES block.

54

a)

b)

Figure 2.1: 1H-NMR spectrum of the representative monomer and polymers obtained by

ADMET: (a) PA-4EES, Mn = 2200 g mol-1 and (b) enlargement showing end-groups for

PA-4EES with two different molecular weights and for the monomer.

55

2.2.7 Post-polymerization reactions

Hydrogenation of the allyl double bond allowed us to obtain PAH-4EES and PAH-

8EES copolymers with more than 99% yield, thus demonstrating that the double bond

remains highly accessible for future reactions, as expected. All copolymers

synthesized were hydrogenated post-reaction. A total absence of peaks related to the

allylic function is noted in NMR spectroscopy (see Figure A.2.10c of the Annexes).

Removing the double bond results in the presence of a tetramethylene aliphatic

spacer. This imparts additional flexibility to the polymer, but may not be sufficient to

favor crystallization via chain folding, since even when taking into account adjacent

ether groups, this chain length is small as compared to the minimum five to eight

bond requirement estimated for most polymers.17–20

However, changing this segment will allow us to verify whether the allylic group is

incorporated into the crystallographic unit, as changing from an allylic group to an

aliphatic chain should provide enough structural variation to induce changes in unit

cell dimensions, conformation and packing, and should therefore result in observable

changes in the X-ray diffraction diagram, as will be discussed later.

To further illustrate the possible modifications of allyl group, chlorination and

bromination reactions were performed on PCA-4EES. These reactions were chosen

for their high yields, and hydrogen atom groups were replaced by chlorine or bromine

atoms in a 99% yield in both cases, as determined by proton NMR spectroscopy (see

Figures A.2.10d and A.2.10e of the Annexes).

56

Table 2.1: Molecular weights and dispersity of polymers synthesized by ADMET

and polycondensationa

Polymers

Reaction conditions

Mn

(NMR)

g mol-1

Mn

(SEC)

g mol-1

Mw

(SEC)

g mol-1

Ip

PA-4EES G2, 1 mol% CH2Cl2, 24 hr, 40 °C 2000 3300 3600 1.1

PA-4EES G2, 6 mol% CH2Cl2, 24 hr, 40 °C - 4900 6400 1.3

PA-4EES HG, 1 mol% CH2Cl2, 24 hr, 40 °C 2200 3600 4000 1.1

PA-4EES HG, 6 mol% CH2Cl2, 24 hr, 40 °C - 6200 8700 1.4

PTA-4EES DMAc, 24 hr,70 °C - 2600 4600 1.8

PTA-4EES DMAc, 48 h, 90 °C - 4100 5700 1.4

PTA-4EES DMAc, 48 h, 120 °C - 900 1500 1.7

PTA-4EES DMAc, 48 h, 150 °C - 900 1200 1.3

PCA-4EES DMAc, 24 hr,70 °C - 4900 8500 1.7

PCA-4EES DMAc, 48 hr,90 °C - 4700 7400 1.6

PCA-4EES DMAc, 48 hr,120 °C - 8400 13 600 1.6

PCA-4EES DMAc, 48 hr,150 °C - 1200 1900 1.6

PTA-8EES DMAc, 24 hr,70 °C - 1700 1900 1.1

PCA-8EES DMAc, 24 hr,70 °C - 1800 4100 2,3

PAE-4EES CH2Cl2, 4 h, 20 °C - 7700 38 000 4.9

aG2: Grubbs second generation catalyst, HG: Hoveyda–Grubbs catalyst.

57

Table 2.2: Proton chemical shifts (d) of the allyl group in cis- and trans

poly(etherethersulfones) obtained by polycondensation and by ADMET (major

configuration trans)

Polymers δ (e) (ppm) δ (f) (ppm)

PA-4EES 4.58 6.10

PTA-4EES 4.58 6.09

PCA-4EES 4.66 5.94

2.2.8 Thermal properties of the copolymers

2.2.8.1 Thermogravimetric analysis (TGA)

Polymers obtained by ADMET and by step-growth polycondensation were

characterized by thermogravimetric analysis (TGA) to investigate their thermal

resistance, one of the assets of PES and PEES. As shown in Figure 2.2, degradation

starts around 370 °C, with a slightly better thermal resistance for the cis polymers.

For the 8-ring polymer, a second degradation step occurs around 550 °C, slightly

above the poly(ethersulfone) homopolymer degradation temperature, which is around

400 °C.21 A decrease in degradation onset temperature as compared to PES was

expected due to the addition of the flexible, aliphatic containing allyl moiety in the

polymer chain.21 This loss in thermal stability is however in part counterbalanced by

the possibility of post-functionalizing the allyl group.

58

Figure 2.2: Thermal stability of representative 4-ring and 8-ring polymers as

determined by thermogravimetry.

2.2.8.2 Differential scanning calorimetry (DSC)

As one of the aims of this work was to tune crystallinity by incorporating a spacer

along the PEES chain, differential scanning calorimetry becomes a method of choice

to investigate these polymers. As mentioned in the Introduction, the temperature

difference between Tg and Tm has been proposed to be one of the main factors

inhibiting crystallization of poly(ethersulfones). DSC can further determine the effect

of thermal history on crystallinity.

Several heating and cooling scans were performed, at a constant speed of 10 °C min-1.

Heating, cooling and reheating scans of one of the polymers, PA-4EES, are reported

in Figure 2.3a. During the first heating scan, two endotherm peaks appear,

corresponding to a double melting behaviour, consistent with the presence of a

crystalline phase. It was difficult to detect the glass transition during this first scan,

indicating a high crystallinity. During the cooling scan, a glass transition is clearly

observed, but no crystallization peak is observed. In the second heating scan, the

59

glass transition still appears, and no melting peaks are observed. This is in agreement

with the reported behaviour of poly(ethersulfones), which do not crystallize readily

after melting.

a)

b)

Figure 2.3: Differential scanning calorimetry: (a) heating and cooling scans for PA-

4EES and (b) first heating scan for representative polymers

60

Figure 2.3b reports the first heating scan of polymers synthesized in this work. The

same general behaviour was observed for all trans-containing polymers (PA-4EES,

PTA-4EES, PTA-8EES), in the presence of a single or double melting peak in the

first scan and only a glass transition in subsequent scans, to which is often

superimposed a relaxation peak. NMR analysis of the PTA-4EES copolymer post-

melting shows that the allyl group is still in its trans form, thus eliminating the

possibility that the incapacity to recrystallize after melting is related to heat induced

isomerization of the allyl group. (NMR spectra are reported Figure A.2.11). In some

cases, a peak may be observed, but as on the second scan, this is replaced at the same

position by a glass transition, it is interpreted as a relaxation peak superimposed to

the glass transition and not as a melt endotherm (PAH-4EES and PCA-4EES). Only

PA-4EES shows a double endothermic peak, which will be discussed separately.

In order to induce crystallization for initially amorphous polymers, or to restore them

after melting for initially crystalline polymers, various annealing treatments between

Tg and Tm (at temperatures varying from 110 to 125 °C) were performed for up to 24

hours. Cooling down to 1° min-1 was also tested from the melt. In all cases, polymers

remained completely amorphous, in keeping with the usual PES and PEES thermal

behaviour. This clearly indicates that the incorporation of an allyl group does not

increase crystallization speed enough to allow annealing-induced crystallization.

The exact position of the glass transition and melt endotherms are reported in Table

2.3. The glass transition temperature varies slightly with the content of cis isomer (Tg

decreases from PC4-EES to PTA-4EES to PA-EES, which contains the least

percentage of cis groups), which is attributed to a higher steric hindrance in the cis

isomer. PTA-8EES stands out as being the lowest molecular weight polymer

synthesized, which explains the observed Tg lower by approximately 20 °C. Upon

hydrogenation of the allyl group, the glass transition endotherms shift to a lower

temperature, in agreement with a higher chain mobility. Upon chlorination and

bromination of the allyl group, hindered mobility due to the size of the substituents

results in a return of the Tg to the value observed for the allyl copolymer. In other

61

synthesized copolymers, no notable effect of molecular weight was observed on

either Tg or melting point. In the 4EES series, the highest Tg was observed for the

ester-linked PAE-4EES. The value is higher by 5 to 10 degrees only, and this increase

could be attributed to the combined effects of chain rigidification by the ester linkage

and to the higher molecular weight of this copolymer. Tg also varies with relative

proportion of EES, this segment being more rigid than the ally spacer. The observed

glass transition temperatures are smaller by approximately 70° to 100 °C than those

of PES (for which values of 205 (ref. 22) to 230 °C (ref. 23) have been reported) or of

PEES (210 °C value reported by Kitipichai et al.).24

The melting points of the synthesized copolymers are also notably different from that

of PEES for which Johnson et al. indicate a value of 310 °C for PEES.21 The highest

value obtained in this work was 179 °C for ester-linked PAE-4EES, again attributed

to the higher chain rigidity and molecular weight of this polymer. For the ether linked

copolymers, the highest melting point observed is the second melting point of PA-

4EES. More importantly, the difference between Tg and Tm remains well below the

usual 100 degrees value observed for most polymers, with values of 32 to 36 °C for

the 4-ring ether-linked block copolymers, 57 °C for the ester-linked 4-ring copolymer

and 72 °C for the ether-linked 8-ring block copolymer. It is therefore a lower

temperature difference than that of PES, which is between 80 to 100 °C, in agreement

with their inability to crystallize upon annealing. Therefore, this factor can be

invoked to explain the lack of crystallization upon annealing, although other factors

must be at play to explain the observed differences from one polymer to another as

synthesized.

Unfortunately, since little is known about the crystal structure of PES or PEES, no

melt enthalpy of the pure crystal form has been reported. It is therefore not possible to

determine accurate crystallinity using DSC-measured melt enthalpy. Nevertheless, if

supposing a value equal to that of poly-(etheretherketone), which are chemically

similar but for which the crystal structure is different,25 crystallinity was estimated

62

and is reported in Table 2.3. Values obtained vary between 0 to 28% for the polymers

as synthesized.

Table 2.3 : Thermal properties and degree of crystallinity χ of copolymers

Mw x 103

g/mol

Tg

°C

Tm1

°C

Tm2

°C

∆Hm

J/g χDSC

%

χX-ray (%)

In.a Rec.a

PA-4EES 6.8 98 133 159 39.5 30 25 37

PA-4EES 8.7 94 130 152 36.2 28 25 37

PTA-4EES 4.1 108 140 - 28.2 22 23 28

PCA-4EES 7.5 115 - - - 0 0 0

PAH-4EES 7.5 105 137 - 10.1 8 18 25

PCA-8EES 4.1 136 - - - 0 0 0

PTA-8EES 1.9 84 156 - 36.0 28 37 42

PAH-8EES 4.1 115 - - - 0 0 50

a In. : Initial, as synthesized Rec.: Recrystallized in a mixture of CH2Cl2 and benzylic alcohol.

2.2.9 X-ray diffraction

X-ray diffraction was performed to investigate the crystallinity of the synthesized

copolymers and to compare their crystalline form. In order to have accurate

information on the peak position, and to eliminate changes associated with the use of

different solvents or temperatures, samples were recrystallized. Annealing was not

useful in this case, as demonstrated by DSC experiments. Only one method has been

published for recrystallizing PES polymers, by slow evaporation of methylene

chloride solutions at low temperatures.26 In the present work, various solvent systems

were tested for PA-4EES. For CH2Cl2 and THF, crystallization was conducted at cold

temperature in order to obtain slow evaporation, following the work of Blackadder et

al.26 For solvents which naturally evaporate slowly, this was not found necessary. X-

ray diffraction diagrams of samples which yielded high crystallinities are reported in

Figure 2.4.

63

Whereas for the PA-4EES copolymer only a slight crystallinity was observed in

CH2Cl2, marked crystallinity could be obtained by using THF, DMAc or NMP.

Polymorphism may be present, as the diffraction diagrams obtained in NMP present

an additional medium-intensity reflection near 47 °C. The best crystallinity was

obtained for a mixture of methylene chloride containing 10% benzyl alcohol with 7

reflections clearly observed in the 20 to 30 °C range, and several lower intensity

reflections observable at higher angles. This solvent system was subsequently used

for all polymers synthesized in this work.

Figure 2.4: X-ray diffraction diagrams of PA-4EES as recrystallized by evaporation

from various solvents

In Figure 2.5a are reported the X-ray diffraction diagrams of the as-synthesized

polymers, along with that of a low molecular weight PES (Mw = 1600 g mol-1, Đ =

1.15) previously synthesized in our group.25 The PES homopolymer is amorphous,

but has a relatively narrow peak width, which may indicate partial organization in the

amorphous phase. Diagrams corresponding to completely amorphous polymers with

64

larger peak width are obtained for the cis-allyl polymers, PCA-4EES and PCA-8EES

as well as one of the two hydrogenated polymers, PAH-8EES.

a) b)

Figure 2.5: X-ray diffraction diagrams of EES-containing copolymers: (a) as

synthesized and (b) after recrystallization by evaporation from dichloromethane–

benzyl alcohol solutions

All other polymers show a superposition of discrete diffraction peaks over the

amorphous halo. Trans-allyl polycondensation PTA-4EES and ADMET PA-4EES

copolymers share the same diffraction peak positions, and similar relative intensities

of the diffraction peaks as compared to the amorphous halo, indicating similar

crystallinities and confirming the DSC results. This similarity also confirms the NMR

results showing that PA-4EES comprises almost exclusively trans-allyl groups.

Crystallinity can be sensitive to the solvent used, which is not the same in both

synthesis methods, but no marked effects were found in this case. Upon

hydrogenation (PAH-4EES), the diffraction diagram changes in terms of peak

65

positions and relative intensities, indicating that a new crystalline form is observed.

This new form is closer to that of PTA-8EES, as the most intense peaks are at the

same position and relative intensities are similar, which may indicate that a similar

conformation and packing is adopted. Upon chlorination, no discrete diffraction

peaks appear, but the ‘amorphous’ peak is very narrow, much narrower than that of

PES, a sign that a mesophase with partial pre-ordering is probably present. Upon

bromination, on the other hand, a few discrete diffraction peaks are observed, but the

crystallinity as-synthesized is low, in agreement with DSC results. Various factors are

most probably at play and affect crystallization, which may include rigidity, steric

hindrance, and electrostatic interactions, and which affect crystallization in an

unpredictable way, the bulkier group (Br) not resulting in the lowest crystallinity.

Finally, the 8-ring hydrogenated polymer is completely amorphous as synthesized.

From these observations, a tendency emerges: cis groups incorporation along the

main chain suppress crystallization of the as-synthesized polymer, whereas trans-

groups promote it. Changes in the dispersity do not affect crystallinity as observed by

X-ray diffraction, as demonstrated by the comparison of PA-4EES and PTA-4EES

diffraction diagrams.

Once the polymers are recrystallized in a slowly evaporating solvent, higher

crystallinities are obtained, and these allow better measurements of peak position and

relative intensities, which are reported in Table A.2.1 of the Annexes. Only two

polymers remain amorphous, the two cis-containing polymers, as seen in Figure 2.5b,

which indicates that the cis group is more effective at suppressing crystallinity than

the 4-carbon aliphatic chain. In this figure is not reported PES, as this polymer does

not have the same crystal form and peak positions as the PEES-based copolymers of

the present work (see Table A.2.1 of the Annexes for a detailed list of peak positions),

and this diagram, which has been previously reported in the literature, would add

little to the discussion here. All other polymers are crystalline to various degrees. The

degree of crystallinity χx−ray was calculated from the relative intensities of the

66

amorphous and crystalline peaks in X-ray diffraction and is reported in Table 2.3. In

all cases, the benzyl alcohol/CH2Cl2 solvent increases crystallinity.

The most impressive increase in crystallinity is noted for PAH-8EES, which did not

crystallize upon synthesis, but becomes the most crystalline polymer (50%

crystallinity) after solvent treatment.

In all cases, peak positions before and after recrystallization remain the same, and so

do relative intensities, although changes occur related to the presence of an important

amorphous halo in poorly crystallized samples. More significantly, peak widths

decrease due to the improvement in crystal phase perfection and in crystallite size,

allowing for a better peak resolution.

As before recrystallization, ADMET PA-4EES and polycondensation trans

copolymer PTA-4EES have almost superimposable diffraction diagrams, indicating

that the decrease in dispersity does not affect noticeably crystallization for this

molecular weight range.

In terms of crystal form, various distinct diagrams are observed. PTA-4EES and

PTA-8EES have a completely different diffraction diagram. Neither corresponds to a

known form of PES, but unfortunately comparison to PEES could not be made, no X-

ray diffraction diagram ever having been obtained to the best of our knowledge for

this polymer.

Observation of a different crystalline form for the 4-ring polymer can be due to

incorporation of the trans-allyl group into the crystallographic repeat unit, the

polymer thus behaving as a different homopolymer, due to the length of the regular

block EES which is very short. This is confirmed by comparing with the diffraction

diagrams of the hydrogenated, chlorinated and brominated copolymers, which are

markedly different, reflecting different crystallographic repeat units and/or packings.

On the other hand, the PTA-8EES and its hydrogenated counterpart have the same

structure, peak positions and relative intensities matching, indicating in this case that

67

the allyl group and the aliphatic chain are excluded from the crystallographic repeat

unit and are therefore segregated in the interlamellar region.

The 4-carbon segment of hydrogenated polymers increases the flexibility of the chain

and entropy of the system, and becomes a better position for chain folds and

reorganization to occur, thus favoring crystallization. On the other hand, trans-allyl

also favors crystallization. Chlorination and bromination result in intermediate

crystallization, thus indicating that packing may be disrupted by steric hindrance.

Molecular models were built to verify whether cis and trans-allyl groups could both

lead to chain folding, and representative examples are shown in Figure 2.6. Models

built show that both the cis and trans groups can lead to chain folding. In both cases,

the number of conformations leading to such chain folds is limited, and a very narrow

window of torsion angles must be adopted, limiting the probability for folding to

occur in such a close packed way. Energies of the trans and cis isomer folds are

similar (6.8 kcal mol-1 for the lowest energy fold built for the cis isomer, and 6.4 for

the trans isomer), but result in small interplanar ring distances (from 3.7 to 5.3 Å

approximately), restricting these chain folds to crystal structures that allow such close

packing. As various pieces of evidence point to the existence of a helical

conformation for PES25 and PEES, such folds may not at the required geometry for

the adopted crystal structures. On the other hand, cis and trans-allyl groups also affect

relative chain alignment, as depicted in Figure 2.6b: due to their geometry and to

unfavorable H/H contacts, cis conformers do not allow a coplanar segment to form,

and chain bifurcation ensues, which may be a reason why this group inhibits

crystallization. On the other hand, trans segments can form extended conformations,

thus favoring chain alignment, leading to the occurrence of pre-crystalline aggregates

which may be precursors to the crystalline phase, in agreement with the theories

proposed by Allegra and Meille27 and by Strobl.28 Finally, the more rigid PAE-4EES

copolymer shows a good crystallinity, thereby indicating that the addition of a rigid

segment next to the EES block favors crystallization

68

a) b)

Figure 2.6: Molecular models of chain folding due to allyl groups: (a) chain fold

models and (b) extended chain conformation, showing deviation from linearity

2.2.10 Double melting behaviour

PA-4EES is the only polymer in this study to exhibit a double melting behaviour,

which is in itself surprising, as PTA-4EES is structurally very similar, with however a

higher dispersity and approximately 4% more cis content. Changes in relative

endotherm intensity of the two peaks have been noted from one synthesis to another,

as shown in Figure 2.7a. These could not be associated with any specific synthesis

conditions or measured properties, and are attributed to random variations during

precipitation conditions.

The double melting behaviour is common to many semicrystalline polymers, and may

be caused by the melting of a secondary structure within the spherulite,29 or to

phenomena such as metastable crystals, secondary crystallization, occurrence of

crystal populations with different crystal forms, shapes, sizes or perfection.30–35 In

order to determine what this double melting endotherm corresponded to in the present

case, samples were heated between Tm1 and Tm2 and then quenched, and the resulting

samples were analyzed by X-ray diffraction, as illustrated in Figure 2.7b. Under these

conditions, the amorphous halo has grown considerably in intensity, denoting partial

melting of the samples. Diffraction peaks remain, as first glance, at the same position

69

as the initial sample. However, the relative intensities of the peaks vary in the 15 to

22° region. Further, the shoulder at 21.5° shifts to 21.0° and becomes a clearly

distinct peak and a new, weak intensity peak appears at 37.5°. These changes indicate

that a slightly different crystal form is present. Further work will be necessary to

ascertain whether this crystal form was present before partial melting but went

undetected due to the similarity in peak positions, or whether a change in the crystal

form occurs during partial melting.

a)

b)

Figure 2.7: Investigation of the double melting behaviour of PA-4EES

a) Representative DSC scans of PA-4EES and b) X-ray diffraction diagrams as

synthesized and after Annealing between Tm1 and Tm2 and rapid quenching

70

2.3 Conclusion

In this work, the objective was to synthesize PEES with an allyl group regularly

inserted in its backbone, and to obtain copolymers which could crystallize and which

could be subjected to post-functionalization reactions, allowing a rapid and

straightforward change in properties. Two synthetic pathways were used: ADMET

polymerization using a Grubbs second generation catalyst or a Hoveyda–Grubbs

catalyst, and traditional step-growth polycondensation.

Regular trans-allyl containing semi-crystalline PEES-based copolymers of moderate

molecular weight and low dispersity were synthesized by ADMET. Polycondensation

was used to obtain cis-allyl and trans-allyl copolymers of relatively low molecular

weights, but higher polydispersities. Even higher molecular weights but also

polydispersity were obtained by replacing the ether linkage between the EES and

allyl groups by an ester linkage. Post-modification was demonstrated by using

hydrogenation, chlorination and bromination reactions, which occurred with more

than 99% yield.

Modulation of crystallization upon design of the chain sequence by regularly

inserting allyl groups was demonstrated. Crystallinity could be totally suppressed by

using cis-allyl groups, whereas incorporation of trans-allyl groups regularly inserted

along the main chain favors crystallization. The 4-ring EES allyl block was too short

for the crystal structure of PEES to be adopted, and instead insertion of the trans-allyl

group in the crystallographic repeat unit occurs, as demonstrated by the change in

diffraction diagram upon hydrogenating this polymer. This is in agreement with a

non-trans conformation of ethersulfone polymers, as proposed previously,25 which

may require more than a single repeat unit for a helix conformation to be adopted.

Changes in the allylic spacer therefore allow partial control of crystallization of this

polymer, and further modulations will be attempted in future work by attaching

various groups at the allyl position, thus investigating the effect of steric hindrance or

of specific interactions.

71

2.4 Acknowledgements

The authors wish to acknowledge the financial support of NSERC (Natural Sciences

and Engineering Research Council of Canada). Help from Pierre Audet (NMR

spectroscopy) and Rodica Plesu (SEC, DSC) of the Département de chimie,

Université Laval is also gratefully acknowledged.

72

2.5 References

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2. Yang Y. S., Shi Z. Q., Holdcroft S., Eur. Polym. J. 2004, 40, 531.

3. Yi Z., Shu L., Cheng L., Zhu B., Xu Y., Polymer 2012, 53, 350.

4. Huang B., Zhu M., Cai M., J. Appl. Polym. Sci. 2011, 119, 647.

5. Hayakawa T., Goseki R., Kakimoto M.-A., Tokita M., Watanabe J., Liao Y.,

Horiuchi S., Org. Lett. 2006, 8, 5453.

6. Colquhoun H. M., Williams D. J., Acc. Chem. Res. 2000, 33, 189.

7. Manet S., Tibirna C., Boivin J., Delabroye C., Brisson J., Macromolecules 2006,

39, 1093.

8. Benoit J.-M., Furtos A., Hudon F., Provencher S., Brisson J., J. Macromol. Sci.,

Part A: Pure Appl. Chem. 2012, 50, 615.

9. Chen Y., Baker G. L., Ding Y., Rabolt J. F., J. Am. Chem. Soc. 1999, 121, 6962.

10. Blundell D. J., Osborn B. N., Polymer 1983, 24, 953.

11. Khatyr A., Maas H., Calzaferri G., J. Org. Chem., 2002, 67, 6705.

12. Plietker B., Niggemann M., Pollrich A., Org. Biomol. Chem. 2004, 2, 1116.

13. Paquette L. A., Fabris F., Tae J.,. Gallucci J. C., Hofferberth J. E., J. Am. Chem.

Soc. 2000, 122, 3391.

14. Tindall D., Pawlow J. H., Wagener K. B., in Alkene Metathesis in Organic

Synthesis, ed. A. F¨urstner, Springer Berlin Heidelberg 1999, vol. 1, pp. 183–

198.

15. Wagener K. B., Brzezinska K., Anderson J. D., Younkin T. R., Steppe K.,

DeBoer W., Macromolecules 1997, 30, 7363.

16. Yang J., Tyberg C. S., Gibson H. W., Macromolecules 1999, 32, 8259.

17. Chum S. P., Knight G. W., Ruiz J. M., Phillips P. F., Macromolecules 1994, 27,

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18. Napolitano R., Pirozzi B., Macromolecules 1998, 31, 3626.

19. Jones N. A, Sikorski P., Atkins E. D. T., Hill M. J., Macromolecules 2000, 33,

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20. Ungar G., Xian-bing Z., Chem. Rev. 2001, 101, 4157.

21. Johnson R. N., Farnham A. G., Clendinning R. A., Hale W. F., Merriam C. N., J.

Polym. Sci., Part A: Polym. Chem., 1967, 5, 2375.

22. Mamo A., Aurelinano A., Battioto S., Cicala G., Samperi F., Scamporrino A.,

Recca A., Polymer 2010, 51, 2972.

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23. Rose J. B., Polymer, 1974, 15, 458.

24. Kitipichai P., Peruta R. L., Korenowski G. M., Wnek G. E., J. Polym. Sci., Part

A: Polym. Chem. 1993, 31, 1365.

25. Benhalima A., Hudon F., Koulibaly F., Tessier C., Brisson J., Can. J. Chem.,

2012, 90, 880.

26. Blackadder D. A., Ghavamikia H., Windle A. H., Polymer 1979, 20, 781.

27. Allegra G., Meille S. V., Adv. Polym. Sci. 2005, 191, 8.

28. Strobl G., Prog. Polym. Sci. 2006, 31, 398.

29. Gardner K. H., Hsiao B. S., Matheson Jr R. R., Wood B. A., Polymer 1992, 33,

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30. Righetti M. C., Di Lorenzo M. L., J. Polym. Sci., Part B: Polym. Phys. 2004, 42,

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31. Yasuniwa M., Tsubakihara S., Ohoshita K., Tokudome S. I., J. Polym. Sci., Part

B: Polym. Phys. 2001, 39, 2005.

32. Yasuniwa M., Tsubakihara S., Murakami T., J. Polym. Sci., Part B: Polym. Phys.

1999, 38, 262.

33. Tan S., Su A., Li W., Zhou E., J. Polym. Sci., Part B: Polym. Phys., 1999, 38, 53.

34. Yasuniwa M., Tsubakihara S., Sugimoto Y., Nakafuku C., J. Polym. Sci., Part B:

Polym. Phys., 2003, 42, 25.

35. Marand H., Alizadeh A., Farmer R., Desai R., Velikov V., Macromolecules,

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74

Chapitre 3: Synthesis of High Molecular Weight

Polyetherethersulfone - Allyl Copolymers of

Controlled glass transition

Adrien Faye, Alexandra Furtos and Josée Brisson

Article à soumettre

75

Résumé

Des polyétheréthersulfones (PEES) ayant des doubles liaisons insérées le long de la

chaîne principale du polymère ont été synthétisés par polycondensation. Les

températures de transition vitreuse ont été modulées par l'augmentation de la

longueur du bloc rigide (étheréthersulfone) et la diminution de celle du segment

flexible qui contient la double liaison. Les copolymères résultants ont des masses

molaires allant jusqu'à 60.000 g.mol-1 et des indices de polydispersité (Ip) peu élevés

(1,70 à 2,11). La distribution aléatoire des monomères dans ces copolymères a été

démontrée par spectrométrie de masse MALDI-TOF et par calorimétrique

différentielle à balayage (DSC), où l’on note une seule température de transition

vitreuse quel que soit le ratio bloc rigide/segment flexible. La résistance thermique

des copolymères augmente lorsqu’on diminue le pourcentage du segment flexible et

qu’on augmente celui du bloc rigide. La chromatographie d'exclusion stérique (SEC)

et les mesures de DSC montrent que la transition vitreuse augmente plus rapidement

avec l'augmentation de la rigidité de la chaîne du polymère qu’avec l'augmentation de

la masse moléculaire. Des films de copolymère ont été fabriqués et leur vieillissement

chimique a été étudié par immersion dans de l'eau de Javel, qui est couramment

utilisée pour nettoyer les membranes. Les films montrent une grande résistance à

l'eau de Javel, rendant ainsi ces copolymères utilisables pour la fabrication de

membranes.

76

Abstract

Polyetherethersulfones (PEES) with double bonds inserted along the main polymer

chain were synthesized by polycondensation. The glass transition was modulated by

extending the aromatic etherethersulfone rigid block and decreasing the length of the

flexible segment which contains the double bond. The resulting copolymers have a

Mn of up to 60,000 g/mol and moderate polydispersity index (Đ or Ip) of 1.70 to

2.11, and are shown by MALDI-TOF mass spectrometry and by the presence of a

single glass transition temperature in differential scanning calorimetry (DSC) to be

random in nature. The thermal resistance of copolymers increases when decreasing

the amount of the flexible segment and increasing the length of the rigid block. Size

exclusion chromatography (SEC) and DSC measurements indicate that the glass

transition increases faster with increasing polymer chain rigidity than with increasing

molecular weight. Copolymer films were manufactured and chemical aging was

investigated by immersion in bleach, which is commonly used to clean membranes.

They show high resistance to bleach, therefore making this approach relevant to

membrane fabrication.

77

3.1 Introduction

Polyethersulfone polymers (PES) and poly(etherethersulfones) (PEES) are widely

used in high-technology applications, such as membrane fabrication for syringe filters

or hollow fiber membranes for microfiltration, ultrafiltration or nanofiltration.1

Membranes made of polyethersulfones usually exhibit high selectivity (high rejection

rate) and a narrow distribution of pore size. They are very resistant to oxidation by

disinfectants such as peroxides or hypochlorites often used for cleaning membranes

after use,2 and can be operated over a wide pH range. They exhibit an excellent

thermal behavior, resisting up to 400 °C, and have glass transition temperatures

which can reach 200 °C.3 They also show interesting mechanical properties and can

easily withstand pressure gradients during filtration operations.

However, polyethersulfone homopolymers offer limited ranges in glass transition

temperatures (Tg), which can be detrimental to some applications. Controlling the

glass transition temperature can be determinant for improving the properties for

existing applications, but also helps to meet additional needs, including the

modulation of the membrane’s separating properties. It is therefore of interest to find

ways to modulate glass transition temperature of PES-based polymers.

PES was synthesized independently, and almost simultaneously by three laboratories:

Union Carbide Corporation4, 5 and 3M Corporation6 in the USA and by the Plastics

Division of ICI7 in the U.K. by two main routes8 using dipolar aprotic solvents such

as dimethylsulfoxyde (DMSO), 1-methyl-2-pyrrolidone (NMP) or dimethylacetamide

(DMAc). 3M Corporation synthesized PES by the polysulfonylation process, a

classical electrophilic aromatic substitution in which arylethers are coupled through

sulfone linkages by a Friedel-Crafts reaction. Union Carbide Corporation and the

Plastics Division of ICI prepared PES by polyetherification, which is a nucleophilic

substitution of activated aromatic dihalides in which sulfone groups are present in the

intermediates, and the ether linkages are formed by displacement reactions.9

https://en.wikipedia.org/wiki/Aprotic

78

Nowadays, the main method used for the synthesis of these polymers is

polycondensation by aromatic nucleophilic substitution at high temperature (180 °C)

generally using dimethylacetamide (DMAc).10 The synthetic route involving a

Friedel-Crafts polycondensation suffers from low reactivity and poor selectivity

compared to nucleophilic aromatic substitution.11

A PEES copolymer in which double bonds were regularly inserted along the

backbone was recently developed by our group, and can be synthesized either by

using acyclic diene metathesis polymerization (ADMET) or regular polycondensation

reaction.12

In the present work, the nucleophilic substitution polycondensation reaction was used

to obtain high molecular weight polyetherethersulfone (PEES) with double bonds

inserted in the polymer chain. Random copolymers were prepared with the aim of

controlling the glass transition temperature. Copolymer films were also prepared, and

their chemical aging was investigated by immersion in bleach.





temperature.


515 HPLC pump, two Agilent PL-Gel Mixed B-LS columns and a RI detector

Optilab 903 model coupled to a LASER Dawn DSP photometer. Monodisperse

polystyrene standards were used for calibration and N-methyl-2-pyrrolidone (NMP)

as eluent at a flow rate of 1.0 mL.min-1. Sample concentration was 5 mg mL-1 and

injection volume was 50 µL. Chromatograms were analyzed with the ASTRA

software version 4.70.07. (Wyatt Technology Corp.) Thermogravimetric analysis

79

(TGA) was performed on a Mettler TGA/SDTA851e/SF/1100 °C equipped with an

MT1 balance under nitrogen atmosphere. Glass transition (Tg) was determined as the

midpoint of the transition using a differential scanning calorimeter (DSC) DSC823e

apparatus from Mettler under nitrogen atmosphere. Indium was used to calibrate the

apparatus prior to use. Scan rate was 10 °C.min-1 and liquid nitrogen was used for

cooling purposes. The STARe software version 9.30 (Mettler Toledo) was used for

data acquisition and processing.

FTIR spectroscopy was carried out on a Thermo Nicolet Magna 850 Fourier

transform spectrometer (Thermo Scientific) equipped with a MCT (mercury cadmium

telluride) detector cooled with liquid nitrogen and a potassium bromide coated

germanium beam splitter i. A Golden-GateTM attenuated total reflection (ATR)

module from Specac Ltd. was used to record attenuated total reflection spectra on a

diamond crystal. The spectral region used covers the mid-infrared, from 750 to 4000

cm-1. All spectra were recorded with 128 interferograms at a resolution of 4 cm-1.

MALDI-TOF mass spectrometry was performed on an Ultraflextreme TOF/TOF

instrument from Bruker Daltonics, equipped with a smart beam laser (355 nm) and

operated in positive reflectron mode at a repetition rate of 1 kHz. The instrument was

calibrated using the monoisotopic mass of the following protonated peptide species:

Bradykinin (1-7) 757.39, Angiotensin II 1046.54, [Glu]-fibrinopeptide-B 1570.67,

ACTH (clip 1-17) 2093.08, ACTH (clip 18-39) 2465.19 and Insulin Chain B oxidized

3495.65. Copolymer samples and dithranol (the MALDI matrix) were dissolved in

dichlorometane at 1 mg/mL and 30 mg/mL respectively. The cationization agent was

a NaI 10 mg/mL solution in THF. A 40 μL aliquot of copolymer solution was mixed

with 20 μL matrix. A drop of this mixed solution was then spotted onto the MALDI

target plate which had been pre-spotted with the cationization agent solution. The

spots were air-dried at room temperature and mass spectra were collected between

m/z 700-10000. The instrument was controlled by FlexControl 3.4 software and data

was processed with FlexAnalysis 3.4, both from Bruker Daltonics.

80

3.2.2 Materials

Bis(4-fluorophenyl) sulfone (99%), 4-methoxyphenol (99%), boron tribromide

(BBr3, 99.9%), N-methyl pyrrolidone (NMP), Dithranol (98%) matrix substance for

MALDI-MS, were all supplied by Sigma Aldrich and used without further

purification. Methylene chloride (CH2Cl2, 99.9%), sodium bicarbonate (NaHCO3,

99.7%), hydroquinone (99%), were purchased from Fisher Scientific and used

without further purification. N,N-dimethylacetamide (DMAc, 99+%) was supplied

by ACP chemical Inc. and dried over magnesium sulfate (MgSO4) or sodium sulfate

(Na2SO4) prior to use. Anhydrous potassium carbonate (K2CO3, 99%) was supplied

by EMD.

3.2.3 Synthesis of the monomer: 4,4’-bis(4-hydroxyphenoxy)

diphenyl sulfone (HPDS)

The monomer was synthesized as reported in reference 12.

3.2.4 Polymers synthesis

3.2.4.1 PEES synthesis10


(17.60 mmol) of anhydrous K2CO3, 2.034g (8.000 mmol) of bis(4-fluorophenyl)

sulfone (FPS) and (0.881 g, 8.00 mmol) of hydroquinone. To this mixture was added

10 mL of DMAc dried over MgSO4 or Na2SO4 and the resulting solution was heated

at 150 °C for 10 hours using an oil bath. Initial monomer concentration was fixed

between 1 and 1.6 mol L-1. After the reaction, the reaction mixture was allowed to

cool to room temperature and precipitated into water, filtered, washed with hot

aqueous sodium bicarbonate (NaHCO3) and NaCl solutions to remove the remaining

DMAc, and dried in vacuo for 24 hours at 80 °C.

http://www.sigmaaldrich.com/catalog/product/fluka/10608?lang=fr&region=CA

http://www.sigmaaldrich.com/catalog/product/fluka/10608?lang=fr&region=CA

81

3.2.4.2 Synthesis of poly(4EES-alt-cb) and poly(4EES-alt-tb)

A round bottom flask (50mL) containing a magnetic stirrer was charged with 1.402g

(10.142mmol) of anhydrous K2CO3, 2.003g (4.610mmol) of 4,4’-bis(4-

hydroxyphenoxy) diphenyl sulfone (HPDS)12 and 0.576 g (4.610mmol) of either (Z)-

1,4-dichlorobut-2-ene (Z-DCB) or (E)-1,4-dichlorobut-2-ene (E-DCB). To this

mixture was added 9.2mL of DMAc dried over MgSO4 or Na2SO4 and the resulting

solution was heated at 75 °C for 24 hours and for 120 °C for another 24 hours using

an oil bath. The initial monomer concentration was set at 1 to 1.6 mol L-1. After the

reaction, the polymers were washed and isolated as described for PEES. Resulting

polymers are named poly(4-etherethersulfone-alternate-cis but-2-ene), abbreviated

poly(4EES-alt-cb), when synthesized using Z-DCB and poly(4-etherethersulfone-

alternate-trans but-2-ene), abbreviated poly(4EES-alt-tb), when using E-DCB, as

shown in Scheme 3.1a.

82

a)

b)

Scheme 3.1: Synthesis of random and alternate copolymers: a) Poly(4EES-alt-cb)

and poly(4EES-alt-tb) alternate copolymers and b) Poly(6EES-ran-4EEScb) random

copolymer (one pot polycondensation reaction)

83

3.2.4.3 Synthesis of poly(6EES-ran-4EEScb)

A round bottom flask (50mL) containing a magnetic stirrer was charged with 0.608g

(4.400mmol) of anhydrous K2CO3, 0.869g (2.000mmol) of 4,4’-bis(4-

hydroxyphenoxy) diphenyl sulfone (HPDS),12 X% mol of bis(4-fluorophenyl) sulfone

(FPS) and Y% mol of (Z)-1,4-dichlorobut-2-ene (Z-DCB) (X and Y quantities used

are reported in Table 3.1). To this mixture was added 4mL of DMAc dried over

MgSO4 or Na2SO4 and the resulting solution was heated in an oil bath at 75 °C for 24

hours, and temperature was raised to 150 °C for an additional 24 hours. The product

was recovered as described for PEES. The resulting polymer is named poly(6-

etherethersulfone-random-4-etherethersulfone-cis but-2-ene) and abbreviated

poly(6EES-ran-4EEScb), as shown in Scheme 3.1b.

Table 3.1: Monomer ratios used in the synthesis of poly(6EES-ran-4EEScb)

mol% FPS mol% HPDS mol% Z-DCB

0 100 100

50 100 50

60 100 40

70 100 30

80 100 20

90 100 10

3.2.5 Copolymer film preparation

0.2 g of a copolymer was dissolved in 5mL of DMAc or NMP, the solution was

filtered, poured into a Petri dish and heated at 100 °C under a hood. After solvent

evaporation, water was added to help lifting the film off from the Petri dish.

3.2.6 Chemical aging studies

Copolymer films having around 5cm in diameter and 75µm thickness were immersed

for one week at room temperature in a commercial bleach solution with a pH adjusted

84

between 10 to 11 using NaOH and HCl. Commercial bleach was supplied by LAVO

PRO 6 company and contained about 26 000 ppm of chlorine.

3.3 Results and discussion

3.3.1 Optimization of the synthesis of poly(4EES-alt-cb) and

poly(4EES-alt-tb)

In this work, the main aim was to prepare copolymers for membrane formation with

varying glass transition temperature. For this purpose, a variation of a previously

developed approach in our group was used: incorporation of allyl groups along the

PES main chain, as shown in Scheme 3.1a.12 However, in the previous work and in

spite of having optimized the reaction temperature, relatively low molecular weights

(Mn = 8400 g/mol) had been obtained, and resulting polymers showed poor film-

forming properties. As the aim was to study the crystal form obtained, such low

molecular weight allowed a better crystallization and this did not cause problems. In

the present work, however, the aim being to prepare films, this was not acceptable.

The reaction was therefore reinvestigated and re-optimized. As reported previously12,

a simple increase in temperature did not raise the molecular weight. Changes in

heating ramp were therefore performed, along with an optimization of reaction time

and monomer concentration. It was found that a combination of higher monomer

concentrations and gradually increasing the temperature in two steps yielded higher

molecular weights, as seen in Table 3.2. Reactions performed at high temperature

resulted in thermal degradation of the monomer, evidenced by the presence of some

brownish to black color in the reaction medium, whereas reactions at low

temperatures resulted in low molecular weights. It was therefore decided to attempt

starting the reaction at a low temperature, where no degradation of the 1,4-but-2-ene

dichloride occurred, and raising to a higher temperature once the polymer chains

started to grow.

85

In the present work, the temperature was maintained at 75 °C for 24 hours and then

raised at 120 °C for additional 24 hours. As reported in Table 3.2, this allowed

obtaining high molecular weights (37,000 g mol-1 for the trans-but-2-ene containing

copolymer and of 64, 800 g mol-1 for the cis-but-2-ene containing copolymer. As in

our previous study12, higher molecular weights are obtained with the cis-containing

copolymer, which is attributed to the high solubility of this copolymer, allowing it to

react longer without precipitating in the solution. These alternated copolymers now

show good film-forming properties. Due to this ease in obtaining higher molecular

weights, and its resistance to thermal and solvent-induced crystallization, the cis-

moiety was selected for further synthesis studies. The related homopolymer

poly(etherethersulfone) (PEES), was also synthesized for comparison purposes.

Table 3.2: Number molecular weight (Mn), degree of polymerization (DP) and

polydispersity index (Ip) of Poly(4EES-alt-tb), Poly(4EES-alt-cb) and PEES

Tg (ºC) Mn (g/mol) DP Ip Yield

Poly(4EES-alt-tb) 118 37,000 66 1.70 77%

Poly(4EES-alt-cb) 113 64,800 113 1.99 93%

PEES 205 36,300 112 1.80 86%

As reported in Table 3.2, resulting copolymers have relatively low glass transition

temperatures (Tg), 113 °C for poly(4EES-alt-cb) and 118 °C for poly(4EES-alt-tb) as

compared that of PEES homopolymer which is 205 °C. These can be major

drawbacks when designing polymers for applications which necessitate high

operating temperatures. A method to modulate the glass transition temperature was

therefore sought.

86

3.3.2 One-pot synthesis of copolymers with longer rigid segments,

poly(6EES-ran-4EEScb)

In order to decrease the effect of the double bonds, polymers with longer rigid

segments were sought. However, as mentioned in our previous work12, although it is

possible to synthesize longer rigid monomers by protection/deprotection means, this

is time-consuming and costly.12 A more simple technique was therefore sought. The

one-pot polycondensation reaction reported in Scheme 3.1b was therefore tested. In

this approach, each HPDS block can react with either a bis(4-fluorophenyl) sulfone

(FPS) or a Z-DCB molecule. By keeping the percentage of HPDS equal to the sum of

FPS and Z-DCB, copolymers with high molecular masses and variable contents of

flexible allylic groups were prepared. However, this simple approach has a price:

polymers obtained are not alternate but can be either block or random. This would be

a problem if optimal crystallization was sought, as any deviation from regularity

decreases the ability of the polymer to assemble in crystal platelets. However, in this

case, this will be an added advantage, further reducing the probability for long-term

solvent or thermal induced crystallization.

Copolymers having ratios of 50/50 to 90/10 FPS and Z-DCB were synthesized. A

100/0 ratio corresponds to pure PEES, 0/100 to the poly(4EES-alt-cb) copolymer.

Values below 50% FPS were not used due to the resulting low glass transition

temperatures. The resulting copolymers have a distribution of rigid aromatic

ethersulfone blocks, which increases chain rigidity of the copolymer. Table 3.3

reports the 6EES/4EEScb ratios used, along with the glass transition temperature and

number average molecular weight. As expected, the glass transition temperatures

increase with EES (etherethersulfone) ratio, since this ratio is that of the most rigid

group. As molecular weight is very sensitive to stoichiometry in polycondensation

reactions, some random fluctuations in molecular weights are observed.

87

Table 3.3: DSC and SEC data of copolymers synthesized with varying 6EES/4EEScb

ratios

6EES/4EEScb ratios Tg (°C) Mn (g/mol) Ip Yield %

0/100 113 64,800 1.99 93

50/50 144 13,800 2.11 97

60/40 154 47,900 1.88 90

70/30 166 52,300 1.95 93

80/20 169 31,700 1.83 96

90/10 175 50,300 1.80 96

100/0* 205 36,300 1.80 86

* corresponding to the polyetherethersulfone homopolymer (PEES)

NMR spectra of the resulting random copolymers are reported in Figure 3.1. The f

and e peaks attributed to the allylic group and peak d corresponding to the aromatic

ring next to the allylic group clearly decrease in intensity when the percentage of the

allylic group (Z-DCB) decreases, thus confirming that the desired copolymers have

been obtained. It is however not possible, using NMR, to determine with certainty

whether the copolymers obtained are random or block in nature.

88

Figure 3.1: 1H-NMR spectra of poly(6EES-ran-4EEScb) random copolymers

3.3.3 MALDI-TOF investigation of the copolymers

MALDI-TOF mass spectrometry was used to investigate the randomness of the

reaction used in the one-pot synthesis. MALDI-TOF of oligomers has previously

been reported and similar conditions were used for the present copolymers.13, 14

89

Unfortunately, only the lower molecular weight species are observed, as seen in

Figure 3.2. This may be caused by preferential ionization or desorption of short

chains, in agreement with previously observed MALDI-TOF results which show, for

some polymers such as PES and PEK, a tendency to favor the ionization of lower

molecular weight species.14, 15 Spectra were also registered using N-methyl-2-

pyrrolidone solutions, with additions of various cationization agents (silver, sodium,

and lithium), but peaks showed even lower intensities and spectra were similar in

nature, but poorer in quality. Therefore, MALDI-TOF results were not used to

determine molecular weights or polydispersities. Nevertheless, they can provide

insights on whether the reaction is truly random at its onset, when the sort chains are

formed, or whether randomization occurs at a later stage.

Figure 3.2 shows representative MALDI-TOF spectra for the PEES homopolymer,

for the alternate copolymers and for the proposed random copolymers, whereas

additional random copolymer spectra are available as Supplementary material. In

both, the homopolymer and in the random copolymer in cases, a Gaussian shaped

distribution of fragments is observed, although this Gaussian is displaced toward low

molecular weights and therefore only half is present for the random copolymer. A

regular spacing is observed in both cases, and it corresponds to 324 m/z units for

PEES and 486 for the alternate copolymer. On the other hand, for the alternate

copolymer, no Gaussian distribution is ever observed. This could be due to poor

ionization or the species, resulting in a poor sampling of the molecular weights.

However, the fact that this is systematic, and that changes in relative intensities of the

fragments are observed with monomer ratio indicates that this may be related to the

nature of the copolymers themselves.

90

a)

b)

c)

Figure 3.2: Representative MALDI-TOF mass spectrum of synthesized copolymers: a)

PEES homopolymer b) Poly(4EES-alt-cb) and c) Poly(6EES-ran-4EEScb), ratio 70/30

91

Table 3.4: Proposed assignment for the main MALDI-TOF fragments of the

PEES homopolymer

Peaks Adducts m/z obs. m/z calc.

J3 [(EES)3-cyclic + Na]+ 995.00 995.12

J4 [(EES)4-cyclic + Na]+ 1319.00 1319.17

J5 [(EES)5-cyclic + Na]+ 1643.00 1643.21

J6 [(EES)6-cyclic + Na]+ 1967.10 1967.26

J7 [(EES)7-cyclic + Na]+ 2291.10 2291.30

J8 [(EES)8-cyclic + Na]+ 2615.20 2615.35

J9 [(EES)9-cyclic + Na]+ 2939.20 2939.40

J10 [(EES)10-cyclic + Na]+ 3263.20 3263.44

J11 [(EES)11-cyclic + Na]+ 3587.30 3587.49

J12 [(EES)12-cyclic + Na]+ 3911.30 3911.53

J13 [(EES)13-cyclic + Na]+ 4235.30 4235.58

J14 [(EES)14-cyclic + Na]+ 4559.30 4559.62

J15 [(EES)15-cyclic + Na]+ 4883.30 4883.67

J16 [(EES)16-cyclic + Na]+ 5207.40 5207.71

J17 [(EES)17-cyclic + Na]+ 5531.50 5531.76

J18 [(EES)18-cyclic + Na]+ 5855.70 5855.81

92


poly(4EES-alt-cb) in the 1000 - 5000 g mol−1 range (only the most intense peaks are

reported in this Table)


K2 [(AB)2-cyclic + Na]+ 995.00 995.21

K3 [(AB)3-cyclic + Na]+ 1481.00 1481.33

K4 [(AB)4-cyclic + Na]+ 1967.10 1967.44

K5 [(AB)5-cyclic + Na]+ 2453.20 2453.55

K6 [(AB)6-cyclic + Na]+ 2939.30 2939.67

K7 [(AB)7-cyclic + Na]+ 3425.30 3425.78

K8 [(AB)8-cyclic + Na]+ 3911.30 3911.89

K9 [(AB)9-cyclic + Na]+ 4397.70 4398.01

K10 [(AB)10-cyclic + Na]+ 4883.30 4884.12

For all the copolymers, masses were used to assign peaks to specific fragments, and

this assignment is reported in Tables 3.4 to 3.7. In these tables, for PEES, Jn peaks

are assigned to cyclic sodium adducts containing n repeat units (EES or

etherethersulfone), as shown in Scheme 3.2. The most intense peaks therefore

correspond to cyclic molecules, which may be due to their higher solubility of to their

easier cationization. The 324 m/z spacing therefore corresponds to the mass of the

EES repeat unit. The observed peak positions are all in good agreement with the

calculated adduct masses, as reported in Table 3.4.

93

Table 3.6: Proposed assignment for the main MALDI-TOF fragments for the poly(6EES-ran-

4EEScb) in the 1000 - 3500 g.mol−1 range (only the most intense peaks are reported in this

Table)


N1 [(AB)2-cyclic + Na]+ 995.00 995.21

N2 [(ABAC)-cyclic + Na]+ 1157.00 1157.19

N3 [(AC)2-cyclic + Na]+ 1319.00 1319.17

N4 [(AB)3-cyclic + Na]+ 1481.10 1481.33

N5 [(ABABAC)d-cyclic + Na]+ 1643.09 1643.30

N6 [(ABACAC)d-cyclic + Na]+ 1805.10 1805.28

N7 [(AC)3-cyclic or (AB)4-cyclic + Na]+ 1967.10 1967.44

N8 [(ABABABAC)d-cyclic + Na]+ 2129.20 2129.42

N9 [(ABABACAC)d-cyclic + Na]+ 2291.20 2291.39

N10 [(AB)5-cyclic or (ABACACAC)d-cyclic + Na]+ 2453.20 2453.37

N11 [(AC)4-cyclic or (ABABABABAC)d-cyclic + Na]+ 2615.30 2615.53

N12 [(ABABABACAC)d-cyclic + Na]+ 2777.29 2777.51

N13 [(AB)6-cyclic or (ABABACACAC)d-cyclic + Na]+ 2939.29 2939.49

N14 [(ABACACACAC)d-cyclic

or (ABABABABABAC)d-cyclic + Na]+ 3101.20 3101.46

N15 [(AC)5-cyclic or (ABABABABACAC)d-cyclic + Na]+ 3263.19 3263.62

N16 [(AB)7-cyclic or (ABABABACACAC)d-cyclic + Na]+ 3425.30 3425.60

dThe position of B and C is random

94

a) Repeat unit of the PEES homopolymer and example of a cyclic adduct

b) Repeat unit of the poly(4EES-alt-cb) alternate copolymer and example of a cyclic

adduct

c) Repeat unit fragments of the random copolymers

(Note: A may react with B and /or C but B cannot react with C)

Scheme 3.2: Repeat units and molar masses of various copolymers reported in the

MALDI-TOF study

95

In the case of the alternate copolymer (Figure 3.2b), the main peak series observed

(peaks Kn) also correspond to cyclic sodium adducts. The observed spacing unit of

486 m/z units also corresponds to the repeat unit of the alternate copolymer (this

repeat being composed of a EES segment combined to the B but-2-ene segment, as

shown in Scheme 3.2b), which is larger in this case due to the addition of the flexible

but-2-ene segment, as illustrated in Scheme 3.2b. Again, the notation used is such that

n corresponds to number of repeat units in the ring or polymer. Smaller intensity

peaks are also observed, and these correspond to polymeric species with different

end-groups and cationization agent. For these, attributions are reported in Table 3.7.

The L peaks correspond to linear poly(4EES-alt-cb) species with H and Cl as end-

groups and H+ as the cationization agent, whereas M peaks correspond to a

poly(4EES-alt-cb) cyclic ions with Li+ as the cationization agent.

Random copolymer spectra are much more complex in nature than can be noticed at

first glance, and many different peak series are observed. The spacing observed of

162 m/z units does not correspond to that of any of the fragments making of the

repeat units, as shown in Scheme 3.2c. It however corresponds to the difference

between the B and C fragments, which is 162 m/z units, indicating that these two

segments occur randomly along the fragments, and therefore in agreement with a

random copolymer.

Detailed peak assignments appear below. It must first be noted that, in this case, the n

number does not correspond to the number of repeat units, contrary to the previous

two cases, but only to the sequence of appearance in the spectra. Attribution of the

most intense N peaks appears in Table 3.6. A first series of peaks, peaks N1, N4, N7,

N10, N13 and N16, correspond again to a cyclic sodium adduct of the (AB)n type

with a spacing of 486, and match those observed for the alternate poly(4EES-alt-cb)

copolymers. A second series is composed of peaks N3, N7, N11 and N15 and

corresponds to all-rigid (AC)n cyclic sodium adducts, with spacing of 648 m/z units,

and therefore some segments but not all also match those of the PEES spectrum. The

third series, peaks N2, N5, N6, N8, N9, N12 and N14, corresponds to sodium adducts

96

of cycles composed of random ABAC segments, with molar masses depending on the

actual number of B and C segments in the adduct. The three peak series will not have

the same relative intensities depending on the B/C ratio, which explains the relative

changes in intensity with B/C ratio, but also the absence of a simple gaussian

distribution. Additional peaks are assigned in Table 3.7, and correspond to lithium

adducts or to linear copolymers, as in the case of the alternate copolymer spectra.

Although MALDI spectra reveal only for small molecular weights fragments, the fact

that these small fragments are random in nature insures that, even at the

polymerization onset, at low temperatures, random chains were obtained. The

temperature was therefore high enough for B and C fragment to react with

approximately equal probability to the A fragments. As the subsequent increase in

temperature occurs when all monomer or almost have reacted, randomization at such

an early stage should insure that the higher molecular weight chain distributions also

exhibit randomization. It is concluded that the two temperature stage one-pot

polycondensation process described here effectively leads to random copolymers.

97

Table 3.7: Proposed assignment for additional MALDI-TOF fragments for the poly(4EES-alt-cb) and poly(6EES-ran-

4EEScb) in the 1000 - 4000 g mol−1 range

Peaks m/Z Obs.

m/Z calc. Adducts

Poly(4EES-alt-cb) Ratio

50/50

Ratio

60/40

Ratio

70/30

Ratio

80/20

Ratio

90/10

L2 1009.00

1009.21 [H-(AB)2-Cl + H]+

Y1

1116.90 1116.90 1116.90 1116.90 1116.21 [Cl-4A-4B-1C-Cl + 2H]+

P1 1141.00 1141.00 1141.00 1141.22 [(ABAC)-cyclic + Li]+

X1

1388.90 1388.90 1388.90 1388.90 1388.27 [H-5A-3B-2C-F + 2H]+

R1 1441.10 1441.10 1441.10 1440.70 1440.26 [Cl-5A-4B-2C-Cl + 2H]+

M3 1465.12

1465.35 [(AB)3-cyclic + Li]+

L3 1495.00

1495.32 [H-(AB)3-Cl + H]+

X2

1550.90 1550.90 1550.90 1550.90 1550.34 [H-6A-5B-1C-F + 2H]+

R2 1603.09 1602.90 1602.90 1602.90 1602.90 1602.33 [Cl-6A-6B-1C-Cl + 2H]+

P2 1627.10 1627.10 1627.33 [(ABABAC)-cyclic + Li]+

X3

1712.99 1712.99 1712.99 1712.31 [H-6A-3B-3C-F + 2H]+

R3 1765.00 1765.00 1765.00 1765.00 1765.00 1764.30 [Cl-B6A-4B-3C-Cl + 2H]+

S1 1838.10 1838.36 [H-7A-4B-2C-H + 2H]+

98

X4

1875.00 1875.00 1875.00 1875.00 1875.34 [F-3A-2B-2C-F + H]+

T1 1897.10 1897.32 [Cl-3A-2B-2C-F + Li]+

R4

1927.20 1926.28 [Cl-6A-2B-5C-Cl + 2H]+

M4 1951.20

1951.47 [(AB)4-cyclic + Li]+

L4 1981.30

1981.43 [H-(AB)4-Cl + H]+

X5

2037.10 2037.10 2037.10 2037.10 2037.32 [F-3A-1B-3C-F + H]+

R5 2088.90 2088.90 2088.90 2088.90 2088.90 2088.44 [Cl-7A-4B-4C-Cl + 2H]

X6

2199.00 2199.00 2199.00 2199.00 2198.34 [H-7A-1B-6C-F + 2H]+

T2 2221.0 2221.46 [Cl-4A-4B-1C-F + Li]+

R6 2250.90 2250.90 2250.90 2250.90 2250.90 2250.42 [Cl-7A-2B-6C-Cl + 2H]+

X7

2361.10 2361.10 2361.10 2361.10 2361.46 [F-4A-3B-2C-F + H]+

R7

2413.10 2413.10 2413.10 2413.10 2412.39 [Cl-8A-4B-5C-Cl + 2H]+

M5 2437.30

2437.58 [(AB)5-cyclic + Li]+

L5 2467.20

2467.55 [H-(AB)5-Cl + H]+

X8

2523.10 2523.10 2523.10 2523.10 2523.43 [F-4A-2B-3C-F + H]+

T3 2545.10 2545.41 [Cl-4A-2B-3C-F + Li]+

R8 2575.20 2574.37 [Cl-8A-2B-7C-Cl + 2H]+

X9

2685.10 2685.10 2685.10 2685.10 2685.41 [F-4A-1B-4C-F + H]+

R9

2737.20 2737.20 2736.44 [Cl-9A-4B-6C-Cl + 2H]+

99

Note: The number preceding A, B, and C corresponds to the number of each A, B and C segment, but does not indicate that

these are linked sequentially. In each case, it is impossible to distinguish between the fragments with the same overall

composition but with different segment alternation.

X10

2847.10 2847.10 2847.10 2847.10 2847.57 [F-5A-4B-2C-F + H]+

R10

2899.20 2899.20 2899.20 2899.20 2898.42 [Cl-9A-2B-8C-Cl + 2H]+

M6 2923.30

2923.69 [(AB)6-cyclic Li]+

L6 2953.30

2953.66 [H-(AB)6-Cl + H]+

R11

3060.20 3060.20 3060.49 [Cl-10A-4B-7C-Cl + 2H]+

X11

3171.20 3171.20 3171.53 [F-5A-2B-4C-F + H]+

M7 3409.50

3409.81 [(AB)7- Li]+

L7 3439.20

3439.78 [H-(AB)7-Cl + H]+

X12

3495.10 3495.10 3495.66 [F-6A-4B-3C-F + H]+

100

3.3.4 Thermal properties of copolymers

3.3.4.1 Thermogravimetric analyses

By decreasing the proportion of allyl groups, it was expected that thermal stability

would increase, as the aromatic moiety is much more heat-resistant than the flexible

allyl segment. Thermogravimetric analyses were performed under a nitrogen flow and

the results are reported in Figure 3.3. For the PEES homopolymer, the degradation

proceeds in one step and starts around 500 °C, while for the copolymers it proceeds in

two steps. For regular alternating copolymers (0/100 ratio), the flexible segments

which are less resistant to heat degrade first from 370 to 425 °C, whereas the rigid

aromatic part degrades at higher temperature, from 500 to 600 °C. By reducing the

proportion of flexible groups (Z-DCB) and increasing the rigid group ratio,

degradation temperatures increase from 370 °C for a Z-DCB (0/100 ratio) to 400 °C

for the 90/10 ratio. Upon decreasing the percentage of flexible segments, the weight

loss during the first degradation decreases, confirming that this first degradation

corresponds to that of flexible but-2-ene segments.

Figure 3.3: Thermogravimetric degradation curves of poly(4EES-alt-cb) (0/100),

PEES homopolymer (100/0) and random copolymers with varying 6EES/4EEScb

ratios

101

3.3.4.2 DSC measurements

Figure 3.4 shows the second heating curve recorded by differential scanning

calorimetry (DSC) on the random copolymers with a scan rate of 10 °C/min. In all

cases, no melt point was observed, in agreement with the previous observation that

the inclusion of cis double bonds inhibits crystallization12 and with the expected

effect of increasing block size randomness along the chain. The glass transition can

clearly be seen, in some cases exhibiting a relaxation peak related to the fast cooling

performed before registering the reported second temperature scan. Whereas the glass

transition temperature of the regular copolymer was considerably smaller than that of

the PEES homopolymer (113 °C vs 205 °C), random copolymers systematically have

a higher glass transition temperature, which is attributed to their lower allylic group

content.

In addition, for all the curves, only one glass transition temperature is observed, and

only limited peak enlargement can be noted, which is compatible with a random

copolymer: block copolymerization should have resulted in blocks with very

different glass transition temperatures (Tgs), and therefore either the appearance of

two Tgs for each copolymer, or a significant enlargement of the Tg of copolymers.

This should be especially visible for the poly(6EES-ran-4EEScb) 90/10 ratio, which

shows a glass temperature difference of more than 60 °C as compared to poly(4EES-

alt-cb).

As shown in Figure 3.5, upon decreasing the proportion of flexible segment (Z-

DCB), glass transition temperatures increase steadily, indicating that copolymers with

high rigidity and small flexibility were obtained. This change cannot be attributed to

variations in molecular weight from one synthesis to another, although such changes

may explain the observed variations in linearity. This variation in Tg is calculated

with eq(3.1) and approximately follows the Gordon-Taylor equation for a copolymer

as reported by Brostow16 :

102

eq(3.1) 𝑇𝑔 = 𝑥1𝑇𝑔1+ 𝐾𝐺𝑇(1− 𝑥1)𝑇𝑔2

𝑥1 + 𝐾𝐺𝑇(1−𝑥1)

where Tg is the glass transition of poly(6EES-ran-4EEScb), Tg1 and Tg2 are

respectively for poly(4EES-alt-cb) and PEES, x1 and x2 are respectively the mass

(weight) fraction of poly(4EES-alt-cb) and PEES in poly(6EES-ran-4EEScb)

copolymer, and a value of kGT = 0.35 was evaluated from a fit between experimental

data and this equation.

Changing the ratio of flexible spacers, as expected, allows modulating glass transition

temperatures. In this range of FPS ratios, glass transition temperatures are all above

100 °C, and this should provide ample thermal resistance for typical polyethersulfone

applications. As observed copolymers obey the Gordon-Taylor equation, it will be

possible to use this equation to adjust the ratio of monomers prior to synthesis to the

desired final Tg of the copolymer.

103

Figure 3.4: DSC curves of poly(4EES-alt-cb) (0/100), PEES homopolymer (100/0)

and random copolymers with varying 6EES/4EEScb ratios

104

Figure 3.5: Changes in glass transition temperatures with varying 6EES weight % in

poly(6EES-ran-4EEScb) copolymers

3.3.5 Chemical aging studies

The most frequent procedure for cleaning the membranes is a back flush with

detergents or bleach to remove particles and fouling. Unfortunately, the sodium

hypochlorite present in bleach, which is efficient to kill micro-organisms, can also

cause membrane degradation. Therefore, polymers which are used to make

membrane must be resistant to bleach. To simulate conditions used in the membrane

industry, chemical aging of copolymer films was performed. Prulho and coworkers2

have shown that the low oxidizability of PES in sodium hypochlorite solution can be

explained in great part by its chemical structure, as it bears no aliphatic groups and

therefore no labile hydrogen to allow chain radical oxidation processes. In the present

case, the but-2-ene segment has an aliphatic group, and the copolymer may be more

susceptible to degradation. Degradation studies are therefore reported for poly(4EES-

alt-cb), which contains a fraction of allylic and aliphatic bonds more susceptible to

degradation. SEC and FTIR spectra were performed on copolymer films after one

105

week immersion in bleach. SEC will inform us if there is cleavage or not of the

polymer chains and FTIR allowed us to have information on the presence or not of

new groups such as carbonyl.

Table 3.8: Number molecular weight (Mn) and polydispersity index (Ip) of

poly(4EES-alt-cb) and poly(6EES-ran-4EEScb) copolymers before and after

immersed in bleach

Copolymers Before immersed After immersed

Mn (g/mol) Ip Mn (g/mol) Ip

Poly(4EES-alt-cb) 64,800 1.99 65,300 1.84

Poly(6EES-ran-4EEScb) 80/20

ratio 31,700 1.83 34,100 1.91

Table 3.8 shows molecular weights and polydispersity indices of copolymers before

and after immersion in bleach. No significant change in molecular weight is observed

or polydispersity, indicating that there is no observable chain cleavage.

Infrared spectra are reported in Figure 3.6. These were scaled using the C-C aromatic

ring valence band at 1580 cm-1 which was considered not to change in intensity even

if degradation occurred. Upon oxidation, carbonyl or hydroxyl groups may be

generated, the most intense bands associated with this modification would appear in

the spectrum in the 1690 - 1750 cm−1 region (C=O valence vibration) and 3400 –

3600 cm-1 (O-H valence vibration). As seen in Figure 3.6, no significant changes are

observed in these spectral regions, thus confirming that oxidation has not taken place.

It is therefore concluded, on the basis of FTIR and SEC results, that no significant

oxidation occurs when exposing the random copolymers to bleach.

106

Figure 3.6: FTIR spectra of poly(6EES-ran-4EEScb) copolymer before and after

immersion in bleach: a) from 500 to 1900 cm-1 and b) from 2600 to 4000 cm-1

107

3.4 Conclusion

High molecular weight ethersulfone–allyl copolymers with double bonds inserted

randomly along the polymer chain have been synthesized by a one-pot

polycondensation process. The random nature of the polymers was demonstrated by

using MALDI-TOF mass spectrometry, although only lower masses appear to be

expressed using this technique. Randomness was confirmed by the observation of a

single, narrow glass transition temperature. The glass transition temperature was

modulated by changes in the allyl/aromatic ether sulfone ratio, which allows

widening their application range. Copolymers show resistance to oxidation by bleach,

used as a disinfectant for industrial membrane applications, making their use in

membrane filtration possible. As demonstrated in an earlier paper, the double bonds

present along the main chain can be used for further polymer modification.



and Engineering Research Council of Canada). Help from Alexandra Furtos of

Université de Montréal (MALDI-TOF), Pierre Audet (NMR spectroscopy) and

Rodica Plesu (SEC, DSC) of the Département de chimie, Université Laval is also

gratefully acknowledged.

108

3.6 References

1. Amirilargani M., Sadrzadeh M., T. Mohammadi, J. Polym. Res. 2010, 17, 363.

2. Prulho R., Therias S., Rivaton A., Gardette J.-L., Polym. Degrad. Stabil. 2013,

98, 1164.

3. Yadav K., Morison K. R., Food Bioprod. Process. 2010, 88, 419-424.

4. Farnham A. G., Johnson R. N., British Pat. 1,078,234, 1963.


Polym. Sci. Part A : Polym. Chem. 1967, 5, 2375.

6. Vogel H. A., British Pat. 1,060,546, 1963.

7. Jones M. E. B., British Pat. 1016245, 1962.

8. Ciobanu M., Marin L., Cozan V., Bruma M., Rev. Adv. Mater. Sci. 2009, 22, 89.

9. Maiti S., Mandal B. K., Prog. Polym. Sci. 1986, 12, 111.

10. Hayakawa T., Goseki R., Kakimoto M.-A., Takita M., Watanabe J., Liao U.,

Horiuchi S. Org. Lett., 2006, 8, 5453.

11. Yonezawa N., Okamoto A., Polym. J, 2009, 41, 899.

12. Faye A., Leduc M., Brisson J., Polym. Chem. 2014, 5, 2548.


Part A : Pure Appl. Chem. 2012, 50, 615.

14. Behrendt J. M., Benstead M., Chaplin A., Wilson B., Turner M. L.,


15. Schriemer D. C., Li L., Anal. Chem. 1997, 69, 4176.

16. Brostow W., Chiu R., Kalogeras I. M., Vassilikou-Dova A., Mater. Lett. 2008,

62, 3152.

109

Chapitre 4: Postfunctionalization by thiol-ene

click reactions of polyetherethersulfone-allyl

copolymers for applications in membrane

filtration

Adrien Faye, Jean-François Morin, Maria Cornelia Iliuta and Josée

Brisson

Article à soumettre

110

Résumé

Des copolyétheréthersulfones, comportant des groupements allyliques comme

espaceurs, ont été fonctionnalisés par greffage de molécules hydrophiles ou

hydrophobes sur des doubles liaisons en passant par les réactions thiol-ène clic. Cette

approche permet, d’une manière simple, de modifier les propriétés du copolymère

pour les adapter à des applications spécifiques, en particulier pour favoriser leur

utilisation dans la fabrication des membranes. Des polyéthylènes glycols (PEG) et des

chaînes aliphatiques en C8 ont été ainsi greffés. Il a été possible de faire réagir une

partie ou toutes les doubles liaisons. Il est également possible de réticuler les films

après fabrication à travers les doubles liaisons non réagies, ce qui permet de diminuer

la solubilité du copolymère, qui augmente après fonctionnalisation. Des mesures

d'angle de contact ont été effectuées sur les films résultants. Les résultats obtenus

indiquent que cette approche permet de moduler l’hydrophilicité des copolymères ou

de les rendre encore plus hydrophobes, selon la nature chimique de la molécule qui y

a été greffée. Les films obtenus sont également relativement résistants à des

températures élevées, ce rend cette approche pertinente pour la fabrication de

membranes.

111

Abstract

Polyetherethersulfone-Allyl copolymers were functionalized by thiol-ene click

reactions to graft hydrophilic or hydrophobic molecules onto the polymer chain,

thereby providing a flexible means of modifying the copolymer properties for use in

membrane fabrication or other applications. Polyethylene glycol (PEG) and aliphatic

C8 chains were thus added. Substitution of all double bonds was achieved, and

modulation of this percentage from 50 to 100% was also performed. Upon

incomplete double bond reaction, the remaining double bonds were used to crosslink

the film post-fabrication and therefore decrease its solubility, which is often a

problem with PEES-based polymers. The hydrophilicity of the resulting films was

investigated by contact angle measurements. This approach permits the modulation of

the hydrophilicity and can lead to solvent-resistant hydrophilic or hydrophobic films.

The resulting films are also relatively resistant to high temperatures, therefore making

this approach relevant to membrane fabrication.

112

4.1 Introduction

Polyethersulfone polymers (PES) are widely used in high-technology applications,

such as membrane fabrication for syringe filters or hollow fiber membranes for

microfiltration, ultrafiltration or nanofiltration.1 Membranes made of

polyethersulfones usually exhibit high selectivity (high rejection rate) and a narrow

distribution of pore size. They are very resistant to oxidation by disinfectants such as

peroxides or hypochlorites often used for cleaning membranes after use,2 and can be

used over a wide pH range. They exhibit an excellent thermal behavior, resisting up

to 400 °C, and have glass transition temperatures (Tg) which can reach 200 °C.3 They

have also interesting mechanical properties and easily withstand pressure gradients

during filtration operations.

In the dairy industry, cheese whey was long considered a waste by-product, but the

use of membranes such as polyethersulfone based membranes now allows to recover

it by separation into individual constituents of high nutritional quality (protein

concentrates for standardization of milk proteins, protein isolates, etc.).3 PES

membranes are also used for industrial production of drinking water, providing a safe,

effective and rapid method for removal of particles, turbidity and micro-organisms.4

However, the use of PES membranes is often limited by their hydrophobic nature,

which leads to membrane fouling by adsorption of proteins and natural organic matter

and by biofilm formation. These eventually block membrane pores and reduce their

flux performance.5-7 Scanning electron microscopy (SEM) observations made by

Wang and coworkers7 show the presence of particle aggregates in the form of a

biofilm on the membrane surface. The extent of adsorption depends on the types of

solute macromolecule/membrane interactions such as hydrogen bonding, dipole

interactions, van der Waals interactions, and electrostatic effects,8 but hydrophobic

interactions have been proposed to be the main factor enhancing protein adsorption

onto the membrane surface.9 When a protein molecule approaches and is in contact

with the surface of hydrophobic polymeric membranes, water molecules between the

113

protein and the membrane surface will be displaced. This causes the protein molecule

to lose its bound water and thus induces conformational changes in its structure,

which result in an irreversible adsorption of the protein onto the membrane surface.10-

11 To maintain membrane permeability and the selectivity, regular chemical cleaning

is required every 18-24 hours.12 This induces oxidative degradation of the membrane

which results in performance decay in many separation applications, significant

reduction in system productivity and increase in system operational cost.4, 11

To reduce this effect, increasing the hydrophilicity of the membranes has been

suggested in the literature.11, 13, 14 Modifying the hydrophilicity of the membranes can

reduce protein adsorption onto the membranes, which will then require less cleaning

up, therefore saving time and money. Further, hydrophilic membranes are easier to

clean since the adsorbed protein molecules are more easily removed from a

hydrophilic surface than from a hydrophobic one.3

One of the strategies used to improve polyethersulfone hydrophilicity is to blend it

with hydrophilic polymers such as polyethylene glycol (PEG). Blending is by far the

simplest method but has limited applicability due to limited miscibility of

hydrophobic and hydrophilic polymers,15 leading to phase separation during the

membrane manufacture. Further, such membranes have poorer mechanical properties.

Mohammadi's group16 showed that by mixing PES with polyacrilonitrile (PAN) in a

weight ratio of 70/30, two layers were observed by SEM, which changes greatly the

membrane structure and performance as compared to neat PES.

In the present paper will be explored the possibility of grafting different molecules

onto polyethethersulfone-allyl copolymer chains. A polyethethersulfone polymer in

which double bonds were regularly inserted along the backbone was recently

developed by our group using acyclic diene metathesis polymerization (ADMET) and

regular polycondensation.17 It was also shown that this double bond can be readily

functionalized to adapt the copolymer properties for specific applications.17 Thiol-

ene click reactions18, 19 are used to graft hydrophilic molecules such as PEG segments

114

and more hydrophobic chains such as C8 alkanes to tailor hydrophilicity of

synthesized copolymers.





temperature.


515 HPLC pump, two Agilent PL-Gel Mixed B-LS columns and a RI detector

Optilab 903 model coupled to a LASER Dawn DSP photometer. Monodisperse

polystyrene standards were used for calibration and N-methyl-2-pyrrolidone (NMP)

as eluent at a flow rate of 1.0 mL min-1. Sample concentration was 5 mg mL-1 and

injection volume was 50 µL. Chromatograms were analyzed with the ASTRA

software version 4.70.07.

Thermogravimetric analysis (TGA) was performed on a Mettler

TGA/SDTA851e/SF/1100 °C equipped with an MT1 balance under nitrogen

atmosphere. Glass transition temperature (Tg) was determined as the midpoint of the

transition using a differential scanning calorimeter (DSC) Mettler DSC823e apparatus

under nitrogen atmosphere. Indium was used to calibrate the apparatus prior to use.

Scan rate was 10 °C min-1 and liquid nitrogen was used for cooling purposes. The

STARe software version 9.30 was used for data acquisition and processing.

An optical contact angle analyzer (OCA 15 Plus, Future Digital Scientific Corp,

USA) was used to measure the contact angles of prepared films with water at 298.2 K

based on the sessile drop method. A small water droplet was deposited on the film

surface and the contact angle was determined from images acquired by a high

resolution camera. A thermostated chamber controlled the temperature using a

115

refrigerated/heating circulator with high precision external temperature control

(Julabo F25-ME). At least three droplets were dispensed on each tested film and a

mean value was reported. Data were measured with an average uncertainty of ±1°.

4.2.2 Materials

Bis(4-fluorophenyl) sulfone (99%), 4-methoxyphenol (99%), boron tribromide

(BBr3, 99.9%), N-methyl pyrrolidone (NMP), 2,2-dimethoxy-2-phenylacetophenone

(DMPA, 99%), 2-(2-(2-chloroethoxy)ethoxy)ethanol (96%), potassium thioacetate

(98%) were all supplied by Sigma Aldrich and used without further purification.

Methanol (99.9%), N,N-dimethylformamide (DMF, 98%), dimethylsulfoxide

(DMSO, 99.9%), methylene chloride (CH2Cl2, 99.9%), sodium bicarbonate

(NaHCO3, 99.7%), hydroquinone (99%), were purchased from Fisher Scientific and

used directly. N,N-dimethylacetamide (DMAc, 99+%) was supplied by ACP

chemical Inc. and dried over magnesium sulfate (MgSO4) or sodium sulfate (Na2SO4)

prior to use. Anhydrous potassium carbonate (K2CO3, 99%) was supplied by EMD.

Thiourea (CH4N2S, 99%) was supply by Riedel-de Haën.

http://en.wikipedia.org/wiki/2,2-Dimethoxy-2-phenylacetophenone

116

Scheme 4.1: Synthesis of 2-(2-(2-hydroxyethoxy)ethoxy)ethanethiol (PEG2-thiol)

4.2.3 Synthesis of S-2-(2-(2-hydroxyethoxy)ethoxy)ethyl thioacetate

(scheme 4.1)20

A round bottom flask (100 mL) containing a magnetic stirrer was charged with 2-(2-

(2-chloroethoxy)ethoxy)ethanol (7.166g, 42.500 mmol, 1eq) and potassium

thioacetate (8.259g, 72.250 mmol, 1.7eq). To this mixture was added 30mL of DMF

dried over MgSO4 or Na2SO4 and the resulting solution was stirred at room

temperature for 5 hours. 50mL of water were then added and the solution was

extracted with methylene chloride. The organic phase was then washed with an

aqueous solution of NaHCO3 and finally with saturated NaCl to remove DMF. This

organic phase was then evaporated off leaving oil which was dried in vacuo for 8

hours at 60 °C to get a pale-yellow oil (6.09g, 29.24 mmol, 69% yield). 1H-NMR 400

MHz ((CDCl3), r.t.): δ 3.73 (t, 2H, 3J = 7.24 Hz), 3.61 (t, 8H, 3J = 7.24 Hz), 3.093 (t,

2H, 3J = 7.24 Hz), 2.95 (s, 1H), 2.34 (s, 3H) ppm;

13C-NMR 400 MHz (CDCl3), r.t.): δ 195.51, 72.46, 70.24, 70.21, 69.67, 61.61, 30.51,

28.67 ppm.

4.2.4 Synthesis of 2-(2-(2-hydroxyethoxy)ethoxy)ethanethiol (PEG2-

thiol) (scheme 4.1)21

S-2-(2-(2-hydroxyethoxy)ethoxy)ethyl thioacetate (5.730 g, 28.800 mmol) was

dissolved in methanol (30 mL). KOH (12 mL, 57.600 mmol, 2eq, 7.200 mol L-1) was

added and the mixture was then heated at 70 °C for 2 hours using an oil bath. The

solution was allowed to cool at room temperature, neutralized with HCl 2M and

extracted with methylene chloride (3 x 20 mL). The organic layer was then dried over

anhydrous magnesium sulfate, filtered, and evaporated off leaving pale-yellow oil

which was dried in vacuo for 8 hours at 40 °C to afford 2-(2-(2-

hydroxyethoxy)ethoxy)ethanethiol (3.45 g, 20.753 mmol, 76%).

117

1H-NMR 400 MHz ((CDCl3), r.t.): δ 3.73 (t, 2H, 3J = 7.099 Hz), 3.65 (t, 8H, 3J =

7.099 Hz), 3.08 (s, 1Hz), 2.71 (t, 3H, 3J = 7.099 Hz), 1.62 (s, 1H) ppm; 13C-NMR 400

MHz (CDCl3), r.t.): δ 72.81, 72.51, 70.25, 70.16, 61.60, 24.14 ppm.

4.2.5 Synthesis of the monomer: 4,4’-bis(4-hydroxyphenoxy)

diphenyl sulfone (HPDS)

The monomer was synthesized as reported by Faye and coworkers17

4.2.6 Polymers and copolymers used in this work

Polymer and copolymer synthesis have been described in Chapter 2 and 3. (Ref

article 2 non encore publié)

Scheme 4.2 : Polymers and copolymers used in this work

118

4.2.7 Post-functionalization of copolymers by thiol-ene click

reactions19

The copolymer was dissolved in methylene chloride or dimethyl sulfoxide (DMSO),

depending on its solubility, using a round bottom glass flask (100 mL) containing a

magnetic stirrer. One equivalent per double bond of thiol-terminated molecule and

0.3% mol of the radical initiator (2,2-dimethoxy-2-phenylacetophenone (DMPA)) per

mol of double bond was then added. The mixture was degassed under vacuum for 5

minutes and bubbled with nitrogen for 10 minutes. The reaction occurred readily at

room temperature by irradiation at λmax 365 nm27, 28 with a 40W UV lamp.

http://en.wikipedia.org/wiki/2,2-Dimethoxy-2-phenylacetophenone

119

Table 4.1: Grafted and cross-linked molecules and their abbreviations

Grafted molecules Abbreviations Functionnalized copolymer

2-(2-(2-hydroxyethoxy)ethoxy) éthanethiol PEG2-thiol Poly(4EES-alt-cb)-graft-PEG2

2,2′-(ethylenedioxy) diethanethiol PEG2-dithiol Poly(4EES-alt-cb)-crosslink-PEG2

1,3-propanedithiol Pr-dithiol Poly(4EES-alt-cb)-crosslink-Pr

1-octanethiol C8-thiol Poly(6EES-ran-4EEScb)-graft-C8

Benzyl mercaptan Benzyl-thiol Poly(6EES-ran-4EEScb)-graft-Benzyl

Poly(ethylene glycol) methyl ether thiol, Mn = 800g/mol PEG16-thiol Poly(6EES-ran-4EEScb)-graft-PEG16

2,2′-(Ethylenedioxy) diethanethiol PEG2-dithiol Poly(6EES-ran-4EEScb)-crosslink-PEG2

120

a)

b)

Scheme 4.3: Thiol-ene click reactions onto poly(4EES-alt-cb) copolymer : a) PEG2-

thiol chain grafting and b) Pr-dithiol and PEG2-dithiol chains cross-linking

121

a)

b)

Scheme 4.4 : Thiol-ene click reactions onto Poly(6EES-ran-4EEScb) copolymer : a)

C8-thiol, Benzyl-thiol and PEG16-thiol chains grafting and b) PEG2-dithiol chain

cross-linking

122

For the poly(4EES-alt-cb) copolymer, the glass transition temperature is already low,

so long flexible (C8-thiol) chains were not grafted, as this would result in lower Tgs

and would affect the mechanical properties.

4.2.8 Solubility test of the cross-linked copolymer

A cross-linked copolymer film with a weight M1 was immersed during 24 hours in

NMP, in which the uncross-linked copolymer is completely soluble. The copolymer

film was then removed from the solvent and dried completely. The mass (M2) of the

dry film was measured. The percentage of solubility was calculated following

Equation (1).

% 𝑜𝑓 𝑠𝑜𝑙𝑢𝑏𝑖𝑙𝑖𝑡𝑦 = 𝑀1 − 𝑀2

𝑀1 × 100 𝑒𝑞(1)

4.2.9 CHNS Elementary Analysis

CHNS elementary analysis was performed on an organic elemental analyzer (Flash

2000, Thermo Scientific). Cystine, used as a standard sample, was put in a universal

soft tin container (100pc, outside diameter = 5 mm, height = 8 mm, volume = 157

μL), which also served as a blank sample. Around 0.5 mg of each sample was

encapsulated in the same type of container. In each case, three samples were

measured, and the reported error was calculated by using the Student’s test with a

95% probability.

The theoretical percentage of carbon element in the expected cross-link copolymer

was calculated as described in the following section, by supposing that there is either

a maximum of one graft or of two grafts attached per double bond, so the molecular

weight of the grated molecule is divided by two or one, respectively.

123

4.2.9.1 Cross-linking with 2,2′-(ethylenedioxy) diethanethiol (PEG2-dithiol)


copolymer after cross-linking (poly(4EES-alt-cb)-crosslink-PEG2), considering

one chain grafted per double bond

The molecular weight of the PEG2-dithiol graft is: M (C6H14O2S2) = 182 g mol-1.

When PEG2-dithiol is grafted, it loses two hydrogen atoms and its molecular weight

becomes 180 g mol-1. The molecular weight of the uncross-linked copolymer unit is:

M (C28H22O6S) = 486 g mol-1.

The molecular weight of the cross-linked copolymer unit is equal to the sum of the

molecular weight of the uncross-linked copolymer unit (486) and the molecular

weight of PEG2-dithiol graft, divided by two (180/2) and a hydrogen atom is added:

M (C31H29O7S2) = 577 g mol-1.

If 𝑥 is the molar mass fraction of the cross-linked copolymer, and 𝑦 the molar mass

fraction, of the uncross-linked copolymer, the sum of the molar mass fractions 𝑥 and

𝑦 is given by, 𝑦 + 𝑥 = 1, and the molecular weight of the cross-linked copolymer is

given by 𝑛(577𝑥 + 486𝑦), where 𝑛 is the number of the cross-linked copolymer

repeat units.

The mass of carbon atoms in the cross-linked copolymer is then equal to 𝑛 (31 ×

12𝑥 + 28 × 12𝑦). The theoretical percentage (𝑎) of carbon atoms contained in the

copolymer after cross-linking is: 𝑎 =31×12𝑥 + 28×12𝑦

577𝑥 + 486𝑦× 100 and therefore:

𝑎 = 372𝑥 + 336𝑦

577𝑥 + 486𝑦× 100

If there are no cross-links, 𝑥 = 0, 𝑦 = 1 and 𝑎 = 69.1%

If all double bonds are cross-linked, 𝑥 = 1, 𝑦 = 0 and 𝑎 = 64.4%

The values obtained from the elemental analysis should therefore be between 64.4

and 69.1% if the approximation that a single chain grafted per double bond is valid.

124


copolymer after cross-linking (poly(4EES-alt-cb)-crosslink-PEG2) considering

two chains grafted per double bond

Similarly, if two grafts are added per double bond, one must change the mass of the

grafted molecule from(180/2) to 180, and the molecular weight of the cross-linked

copolymer unit with the two grafts becomes M (C34H34O8S3) = 666 g mol-1 instead of

M (C31H29O7S2) = 577 g mol-1. The theoretical percentage (𝑎) of carbon atoms

contained in the copolymer after cross-linking in this case is: 𝑎 =34×12𝑥 + 28×12𝑦

666𝑥 + 486𝑦×

100 and therefore:

𝑎 = 408𝑥 + 336𝑦

666𝑥 + 486𝑦× 100



4.2.9.2 Cross-linking with 1,3-propanedithiol (Pr-dithiol)


copolymer after cross-linking (poly(4EES-alt-cb)-crosslink-Pr)

Using the molar mass of the Pr-dithiol graft (M(C3H8S2) = 108 g mol-1), similarly,

one obtains:

If a single graft exists per double bond: 𝑎 =29.5×12𝑥 + 28×12𝑦

540𝑥 + 486𝑦× 100 and therefore:

𝑎 = 354𝑥 + 336𝑦

540𝑥 + 486𝑦× 100



125

And, if two chains are grafted per double bond: 𝑎 =31×12𝑥 + 28×12𝑦

592𝑥 + 486𝑦× 100 and

therefore:

𝑎 = 372𝑥 + 336𝑦

592𝑥 + 486𝑦× 100

If there is no cross-link, 𝑥 = 0, 𝑦 = 1 and 𝑎 = 69.1%


4.2.10 Cross-link density measurements

Cross-link density measurements of the cross-linked copolymer were performed

using a swelling method described in a previous paper by Liang and coworkers.22 A

copolymer film was cut in a small piece, weighted and submerged in toluene.

Samples were allowed to swell for 72 hours at room temperature in a Petri dish which

was covered and protected from light to reach equilibrium. After 72 hours, excess

solvent was removed using a pipet without touching the swollen film pieces. Each

film piece was then lightly dabbed with absorbent paper and immediately weighted

accurately.

The cross-link density, which corresponds to the number of moles of cross-links per

gram of insoluble network, and the number average molecular weight between cross-

links (𝑀𝑐) were calculated using the following equations23, 24:

𝑀𝑐 = 𝜌𝑉𝑠(𝑉𝑝

13 −

𝑉𝑝𝑟

2)

−𝐿𝑛[(1 − 𝑉𝑝) + 𝑉𝑝 + 𝜒𝑉𝑝2]

where 𝜌 is the density of polymer (g cm-3) and 𝑉𝑠 is the molar volume of solvent (cm3

mol-1), given by: 𝑉𝑠 = 𝑀𝑠

𝑑𝑠, Ms is the molar mass of the solvent (g mol-1) and 𝑑𝑠 is

the density of solvent (g cm-3).

𝑉𝑝 is the volume fraction of the copolymer in the swollen gel at equilibrium, given by

126

𝑉𝑝 = 𝑚𝑝 × 𝑑𝑠

𝑚𝑝(𝑑𝑠 − 𝑑𝑝) + 𝑚𝑡 × 𝑑𝑝]

𝑚𝑝 is the weight of the copolymer before swelling

𝑚𝑡 is the weight of the copolymer after swelling (polymer + solvent) at equilibrium

𝑑𝑝 is the density of the copolymer (g cm-3)

𝑉𝑝𝑟 is the volume fraction of the copolymer in the relaxed network state i.e., when

cross-linking is introduced, and is related to 𝑉𝑝 by the following equation:

𝑉𝑝 + 𝑉𝑝𝑟 = 1

is the copolymer - solvent interaction parameter, given by:

𝜒 = 𝛽 +𝑉𝑠

𝑅𝑇(𝛿𝑠 − 𝛿𝑝)

where 𝛽 is the lattice constant, usually about 0.3423

𝑅 is the universal gas constant

𝑇 is the absolute temperature

𝛿 is the solubility parameter and the subscripts 𝑠 and 𝑝 refer to the solvent and

copolymer, respectively.

Finally, the molecular weight between chain entanglements is related to the cross-link

density by the following equation:

𝐶𝑟𝑜𝑠𝑠𝑙𝑖𝑛𝑘 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 = 1

2 × 𝑀𝑐

where 𝑀𝑐 is the number average molecular weight between cross-links.

A value of 8.94 MPa1/2 was used for the solubility parameter of the toluene solvent.25

PES has a chemical structure similar to that of the copolymer studied here, and as a

first approximation, the values for PES reported by Rizwan and coworkers26 have

been used in this work: the density of PES (1.37 g cm-3), and the overall solubility

parameter of PES (24.19 MPa1/2).

127

4.2.11 Copolymer film preparation

0.2 g of a grafted copolymer was dissolved in around 5mL of DMAc or NMP, the

solution was filtered, poured into a Petri dish 5cm in diameter and heated at 100 °C

under the hood. After solvent evaporation, water was added to help peeling off the

film from the Petri dish. The films have around 5cm in diameter and 75µm in

thickness.

4.2.12 Cross-linked copolymer film preparation

After reaction, the solution was filtered and poured into a Petri dish to evaporate the

solvent. After evaporation, an insoluble film was obtained. It was immersed in water

and then methanol to remove impurities, and finally dried under vacuum at 60 ºC for

24 hours.

4.3 Results and discussion

4.3.1 PES and PEES

In this work, PES and PEES were synthesized to compare their hydrophilicity and

thermal properties with the synthesized copolymers.

Table 4.2: Number molecular weights (Mn), degree of polymerization (DP) and

polydispersity index (Ip) of synthesized polyethersulfone (PES) and

polyetherethersulfone (PEES)

Mn (g/mol) DP Ip Yield

PES 25,100 108 1.70 93%

PEES 36,300 112 1.80 86%

128

4.3.2 Alternate and random copolymer synthesis

Alternate and random copolymers were synthesized as described in Chapter 3 and

directly functionalized by thiol-ene click reactions. Their molecular weight,

polydispersity index, glass transition temperature and contact angles are reported in

Table 4.3.

4.3.3 Post-functionalization of copolymers by thiol-ene click reactions

Thiol-ene click reactions were performed to functionalize the copolymers synthesized

in this work using DMPA (2,2-dimethoxy-2-phenylacetophenone) as a photoinitiator,

as shown in Schemes 4.3 and 4.4. In this work, the goal of functionalization was to

make films with controlled hydrophilicity. The allyl double bond was therefore

functionalized using different molecules such as PEG2-thiol, PEG2-dithiol,

octanethiol, benzyl mercaptan, propanedithiol (Table 4.1), and hydrophilicity of

resulting copolymers was evaluated by contact angle measurements (Table 4.3).

After grafting PEG2-thiol onto poly(4EES-alt-cb) copolymer, FTIR spectra were

recorded to verify if the reaction had proceeded. FTIR spectra (Figure 4.1) were

normalized according to the intensity of the peak at 1586 cm-1, attributed to the

phenyl groups, which are expected to change in intensity after the reaction (Figure

4.1a). The FTIR spectrum of the functionalized copolymer (poly(4EES-alt-cb)-graft-

PEG2), represented by a full line (Figure 4.1b), shows an increase in the peak

intensity of the (C-H) stretching of aliphatic groups around 2900 cm-1, attributed to

the grafting of PEG2-thiol. The presence of a (OH) vibration around 3400 cm-1 is

further proof that the reaction has proceeded.

129

Table 4.3: Number molecular weight, polydispersity index, glass transition temperature and

contact angles of copolymers and functionalized copolymers

Copolymers Mn (g/mol) Ip Tg

(°C)

Contact

angle (°)

PES 25,100 1.70 236 88

PEES 36,300 1.80 205 82

Poly(4EES-alt-cb) 64,800 1.99 104 95

Poly(4EES-alt-cb)-graft-PEG2 9,000 2.10 83 69

Poly(4EES-alt-cb)-crosslink-PEG2 Insoluble insoluble 101 72

Poly(6EES-ran-4EEScb) 21,900 2.03 176 87

Poly(6EES-ran-4EEScb)-graft-C8 15,800 2.09 109 98

Poly(6EES-ran-4EEScb)-graft-Benzyl 22,100 2.21 127 94

Poly(6EES-ran-4EEScb)-graft-PEG16 12,800 2.09 95 60

Poly(6EES-ran-4EEScb)-crosslink-PEG2 partially

insoluble

partially

insoluble 92 78

For the Pr-dithiol, the resulting cross-linked polymer is partially soluble and degrades

at 130 °C before the glass transition temperature can be observed.

130

a)

b)

Figure 4.1: FTIR spectra of poly(4EES-alt-cb) and poly(4EES-alt-cb)-graft-PEG2: a) from 700

to 1900 cm-1 and b) from 2500 to 4000 cm-1

The reaction is also confirmed by NMR spectrometry (Figure 4.2) where a decrease

in intensity of peaks related to the double bond (e and f) is observed for the

poly(4EES-alt-cb)-graft-PEG2 copolymer as compared to that of the original

131

copolymer (poly(4EES-alt-cb)). The appearance of a peak around 3.4 ppm attributed

to the ethylene group of the grafted molecule confirms that PEG2-thiol is grafted onto

the copolymer through the double bond. From the integration of the NMR peaks of

both functionalized and original copolymers, it is found that 65% of double bonds

have reacted in the example reported in Figure 4.2.

Figure 4.2: 1H-NMR spectra of Poly(4EES-alt-cb) and Poly(4EES-alt-cb)-graft-

PEG2

It is possible to functionalize all double bonds by adjusting the amount of the

molecule to be grafted, as was demonstrated in Chapter 2. In the present work, this

was not the objective: some double bonds were needed to perform cross-linking

reactions after film fabrication, in order to increase their resistance to solvents, that is

to say decrease their solubility.

132

Using the same reasoning, it can be demonstrated that the PEG16 was grafted onto the

double bond of polymer chains by considering FTIR and NMR spectra of the original

and grafted copolymer (Figures 4.3 and 4.4).

All molecules represented in Table 4.1 were used for grafting or cross-linking.

Additional FTIR and NMR spectra confirming that grafting and cross-linking

procedures have been successful are reported in the supporting information.

a)

b)

133

Figure 4.3: FTIR spectra of Poly(6EES-ran-4EEScb) and Poly(6EES-ran-4EEScb)-

graft-PEG16 a) from 700 to 1900 cm-1 and b) from 2500 to 4000 cm-1

Figure 4.4: 1H-NMR spectra of Poly(6EES-ran-4EEScb) and Poly(6EES-ran-

4EEScb)-graft-PEG16

FTIR confirms that the cross-linking reactions were successful. Attempts at

quantification of the cross-linking were done using three methods:

1) Solubility decreased from 100% for the copolymer used for the cross-linking

reactions to 10% and 26% (Table 4.4) when, respectively, the PEG2-dithiol or the Pr-

dithiol was used to cross-link the polymer, which confirms that cross-linking has

occurred, but also indicates that part of the chains remain uncross-linked.

2) Swelling in toluene was used to estimate the molecular weight between

entanglements (Table 4.4). The difficulty in this case resides in determining the

correct values for the polymer solubility parameter and for the polymer density.

Values reported for PES26 were used in this case but this is an approximation, which

134

further varies in magnitude depending on the chemical nature of the cross-linking

agent used. Nevertheless, values obtained are in the order of 2000 g mol-1 for the

PEG2-dithiol and 3000 g mol-1 for the Pr-dithiol, which fits with the observation of a

higher solubility and therefore lower crosslink density achieved for the latter

polymer.

3) A final attempt to quantify the crosslink density was to use elementary analysis to

estimate compositional changes and correlate these to the addition of cross-links. The

theoretical percentage of carbon was calculated for a perfect, uncross-linked polymer

and for the same perfect polymer when 100% cross-links were added, both for the

PEG2-dithiol and Pr-dithiol cross-links. Two cases were considered: one cross-linking

per double bond, an hydrogen being attached also to the double bond upon reaction,

or two cross-links per double bond, which could correspond either to the chains being

attached by only one end, and therefore not consisting in a crosslink, or to chains

attached by both ends, but with two grafts attached by double bond, both possibilities

giving comparable carbon percentages.

Results shown in Table 4.4 indicate that a reasonable but not perfect fit between

observed and calculated values for the non cross-linked copolymer, the observed

quantity of carbon being lower than expected. This may be attributed to the presence

of imperfections in the copolymer or to inorganic impurities which would lower the

observed carbon content, therefore indicating that these measurements are semi-

quantitative.

Upon cross-linking, if only one cross-link is created per double bond, the percentage

of the carbon is expected to decrease for the both PEG2-dithiol and Pr-dithiol. If two

chains are attached by double bond, both carbon contents are expected to decrease.

Experimental values are lower for both cross-linked copolymers than for the original

uncross-linked copolymer, consistent with a reaction having occurred. Values are

lower than those calculated for the 100% cross-linked copolymer having one cross-

link per double bond, and show a better fit with values calculated for two double

cross-links per double bonds. Nevertheless, as in the case of the uncross-linked

135

copolymer, values are still lower than the expected minimum values that the

calculated values represent.

Although semi-quantitative, these values are consistent with a large proportion of

cross-links having been added to the copolymer.

Table 4.4: Carbon elementary analysis and solubility of copolymers cross-linked with

PEG2-dithiol and Pr-dithiol.

% carbon

obs.

% carbon calc.

(1 graft/double

bond)

% carbon calc.

(2 grafts/double

bond)

Solubility Mc

(swelling)

(g mol-1)

Alternating

copolymer 68.0 ± 0.5 69.1 69.1 100% -

Alternating

copolymer

cross-

linked with

PEG2-

dithiol

59.1 ± 0.5 64.4 61.2 10% 2000

Alternating

copolymer

cross-

linked with

Pr-dithiol

60.4 ± 0.5 65.5 62.8 26% 3000

4.3.4 Hydrophilicity and hydrophobicity studies

In order to evaluate the effect of the different modifications on copolymer

hydrophilicity, contact angles of PEES and of the original and functionalized

copolymers were measured. Static water contact angles of all samples are reported in

Table 4.3.

Figure 4.5 shows that the contact angle of PEES is smaller than that of PES,

indicating that PEES is more hydrophilic than PES. This result was expected as there

are more ethers (hydrophilic nature) in the PEES than in PES. This partly explains the

136

fact that PEES was chosen, the objective of this work being to increase the

hydrophilic nature of PES-based membranes to reduce clogging of the membranes.

It is noted in Figure 4.5 that, by grafting hydrophobic molecules such as alkyls onto

the poly(4EES-alt-cb) chain, contact angles of the resulting copolymers increase as

compared to that of PEES, indicating that hydrophilicity decreases. By grafting PEG

molecules which are hydrophilic, contact angles of resulting copolymers decrease as

compared to that of the original copolymer, and hydrophilicity increases. It is

therefore possible to decrease or increase the hydrophilicity of copolymers either by

grafting a hydrophobic or hydrophilic molecule, i.e. hydrophilicity can be modulated.

This result is very important because it indicates that it is possible to tailor the

properties of PEES copolymers for well-defined applications.

Figure 4.5: Contact angles of PES, PEES, alternate copolymer (Poly(4EES-alt-cb)),

and alternate copolymer after cross-linking or grafting

The same trend was also noted for random copolymers (Figure 4.6), but much longer

chains are then required to obtain the same effect since the number of double bonds,

137

and therefore of possible grafts, is smaller in the random copolymer than alternating

copolymer.

Figure 4.6: Contact angles of the random copolymer (Poly(6EES-ran-4EEScb))

before and after grafting or cross-linking

4.3.5 Film cross-linking

Cross-linking of already prepared films of Poly(6EES-ran-4EEcb) was performed to

compare their hydrophilicity and their solvent resistance with other copolymers

functionalized after complete dissolution (solution reaction). Due to the solid nature

of the film, it is supposed that cross-linking is mainly performed at the film surface,

although solvent penetration and therefore reactions are also possible in the whole

film thickness.

FTIR spectra presented in Figure 4.7 show that the reaction has taken place, as the

relative intensity of the (C-H) aliphatic vibration band has increased. It is also

noticed that, after reaction, the glass transition temperature increases from 148 °C to

138

153 °C at a scan rate of 20 °C/min, which also confirms that cross-linking has

occurred, as a cross-linked polymer will need more energy before the chains can

show long-range movement , hence a higher Tg is observed. The film also becomes

more hydrophilic after cross-linking, as the contact angle decreases from 87° (before

cross-linking) to 54° (after cross-linking). Finally, it becomes highly solvent resistant,

being insoluble even in NMP.

As compared to initial poly(6EES-ran-4EEScb)-crosslink-PEG2 (see Table 4.3)

functionalized with the same hydrophilic molecule (PEG2-dithiol), the cross-linked

copolymer film has a higher glass transition temperature (153 °C vs 92 °C) and a

lower contact angle (54° vs 78°), and is therefore also more hydrophilic.

Table 4.5: Glass transition temperatures and contact angles of Poly(6EES-ran-

4EEScb) before and after surface cross-linking

Poly(6EES-ran-4EEScb)

before surface cross-

linking

Poly(6EES-ran-4EEScb) after

surface cross-linking

Tg (°C) 148 153

Contact angle (°) 87 54

139

a)

b)

Figure 4.7: FTIR spectra of Poly(6EES-ran-4EEScb) before and after surface-

cross-linking

140

4.4 Conclusion

In this work, the aim was to functionalize poly(4EES-alt-cb) and poly(6EES-ran-

4EEScb) with hydrophilic or hydrophobic molecules to modulate their properties and

eventually those of PES-based membranes. Post-functionalization reactions were

carried out using the thiol-ene click reaction, allowing rapid and straightforward

changes in properties. Various chains were grafted, including hydrophobic 1-

octanethiol, 1,3-propanedithiol and benzyl mercaptan chains, as well as hydrophilic

PEG2-thiol, PEG2-dithiol and PEG16-thiol chains.

Cross-linking was investigated by FTIR, DSC, solubility and swelling measurements,

and finally CHNS analysis.

Contact angle measurements were performed on films prepared using these modified

copolymers, and show that hydrophilicity of these copolymers can be easily

modulated by this approach. This will allow to make hydrophilic membranes based

on polyethersulfones polymers, to prevent clogging during filtration of protein-

containing substances, and thus increasing the lifetime of resulting membranes.

Unfortunately, hydrophilic grafts also decrease Tg and increase polymer solubility,

which is detrimental to membrane properties. Cross-linking of film surface using

hydrophilic molecules was therefore performed to circumvent these problems. Films

were first prepared from solution evaporation, and then dipped into the reaction

mixture using methanol as solvent, after which they were submitted to thiol-ene click

reactions with a PEG2-dithiol. Resulting films shows a combination of increased

hydrophilicity, Tg and solvent resistance.

141



and Engineering Research Council of Canada). Help from Maria-Cornélia Iliuta of

Génie chimique (contact angles measurements), Pierre Audet (NMR spectroscopy)

and Rodica Plesu (SEC, DSC) of the Département de chimie, Université Laval is also

gratefully acknowledged.

142

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3. Yadav K., Morison K. R., Food Bioprod. Process. 2010, 88, 419.

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5. Zhao W., He C., Wang H., Su B., Sun S., Zhao C., Ind. Eng. Chem. Res. 2011,

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6. Van der Bruggen B., Braeken L., Vandecasteele C., Sep. Purif. Technol. 2002,

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7. Wang S., Liu C., Li Q., Water Res. 2011, 45, 357.

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11. Zhao Y.-H., Zhu X.-Y., Wee K.-H., Bai R., J. Phys. Chem. B 2010, 114, 2422.

12. Tang X., Flint S. H., Bennett R. J., Brooks J. D., J. Membr. Sci. 2010, 352, 71.

13. Liu S. X., Kim J.-T., J. Adhes. Sci. Technol. 2011, 25, 193.

14. Reddy A. V. R., Mohan D. J., Bhattacharya A., Shah V. J., Ghosh P. K., J.

Membr. Sci. 2003, 214, 211.

15. Van der Bruggen B., J. Appl. Polym. Sci. 2009, 114, 630.

16. Amirilargani M., Sabetghadam A., Mohammadi T., Polym. Advan. Technol.,

2012, 23, 398.


18. Bantchev G. B.,. Kenar J. A, Biresaw G., Han M. G., J. Agric. Food. Chem.

2009, 57, 1282.

19. Lluch C., Ronda J. C., Galià M., Lligadas G., Cadiz V., Biomacromolecules

2010, 11, 1646.

20. Wu S., Huang X., Du X., Angew. Chem., 2013, 125, 5690.

21. Sigma-Aldrich., Technical Bulletin AL-267, Thioacetate Deprotection

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22. Liang H., Hardy J.-M., Rodrigue D., Brisson J., Rubber Chem. Technol. , 2014,

87, 538.

143

23. BarlkanI M., Hepburn C., Iran. J. Polym. Sci. Technol. , 1992, 1, 1.

24. Isabel E. P., Jesus M. M., Rosa G.-A. M., Inés F. P., J. Appl. Polym. Sci., 2007,

103, 263.

25. Belmares M., Blanco M., Goddard W. A., III, Ross R. B., Caldwell G., Chou S.-

H., Pham J., Olofson P. M., Cristina T., J. Comput. Chem. 2004, 25, 1814.

26. Rizwan N., Hilmi M., Zakaria M., Int. J. Sci. Eng. Technol. 2014, 3, 450.

27. Dondoni A. Marra A., Chem. Soc. Rev. 2012, 41, 573.

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144

Chapitre 5 : Conclusion et Recommandations

Ce travail avait pour objectif de synthétiser les PES avec incorporation d’un

groupement post-fonctionnalisable pour contrôler la cristallinité, les températures de

transition vitreuse et l’hydrophilicité des copolymères résultants. Deux méthodes de

synthèse ont été utilisées : la polymérisation par métathèse des diènes acycliques

(ADMET) et la polycondensation classique. Au début du projet, nous comptions sur

l’ADMET pour synthétiser les copolymères mais plusieurs raisons ont fait que nous

avions ensuite utilisé la polycondensation. Une première raison est le coût du

catalyseur : Les catalyseurs de Grubbs nécessaires pour ce type de réaction sont assez

dispendieux, ce qui rend cette méthode de synthèse coûteuse. Cependant, la raison

principale est reliée aux limites de l’ADMET pour ce type de synthèse. D’une part, le

choix du solvant posait problème, d’autre part, certains groupements présents dans le

monomère pouvaient interagir avec le catalyseur et le désactiver. Les polymères ne

sont complètement solubles que dans les solvants polaires comme le NMP, le DMF,

le DMAc ou le DMSO, mais ces solvants interagissent tous avec les catalyseurs de

Grubbs, donc nous ne pouvions pas les utiliser. Nous avons alors utilisé le

dichlorométhane qui est un solvant approprié pour l’ADMET d’après Schulz et al.1

mais, à des taux de conversion élevés, le polymère devient partiellement soluble dans

ce solvant. Le flux d’azote imposé pour faire évaporer l’éthylène formé lors de la

réaction et éviter une réaction réversible cause également un problème car le

dichlorométhane s’évapore en même temps, laissant le milieu réactionnel dépourvu

de solvant.

Finalement, un autre facteur limitant concerne la liaison de coordination

intramoléculaire qui peut se créer entre les doublets libres de l’atome d’oxygène

proche de la double liaison et le métal central du catalyseur, ayant pour conséquence

la désactivation complète du catalyseur. Wagener et al.2 ont étudié la possibilité de la

formation de cette liaison intramoléculaire et ont conclu qu’il faudrait trois (3)

groupements méthylène entre l’oxygène et la double liaison pour éviter la formation

145

de ce complexe intramoléculaire. Dans le cas du polymère étudié ici, il y a un seul

groupement méthylène entre l’oxygène et la double liaison. Ceci explique les faibles

masses molaires obtenues, valeurs qui variaient peu avec la quantité de catalyseur

utilisée. Les taux de conversion sont également très faibles. En raison de ces faibles

masses molaires, nous étions incapables de fabriquer des films résistants avec ces

copolymères. Or, la principale application visée dans ce projet est la fabrication de

membranes, ce qui nécessite des polymères de masses molaires élevés. Nous n’avons

pas voulu augmenter la longueur du segment flexible pour ne pas compromettre les

propriétés mécaniques du copolymère résultant, et avons donc abandonné cette

méthode de synthèse dans les travaux subséquents.

Schéma 5.1 : Illustration de la possibilité d’une liaison intramoléculaire entre

l’oxygène proche de la double liaison et le métal central du catalyseur2

C’est ainsi que nous avons eu recours à la polycondensation classique en faisant

réagir un bloc rigide avec un monomère de configuration cis ou trans pour obtenir,

respectivement, un copolymère de configuration cis ou trans. Les monomères

flexibles utilisés pour la polycondensation sont accessibles et très économiques. Le

bloc rigide est facile à synthétiser avec des rendements de plus 90%. Son architecture

très simple permet de sauver une étape dans la synthèse en comparaison au

monomère utilisé pour l’ADMET. La synthèse par polycondensation nous a permis

d’obtenir des copolymères de hautes masses molaires (jusqu’à des Mn de plus 60 000

g.mol-1) avec des taux de conversion élevés.

146

Avec le monomère de configuration trans, le copolymère résultant est semi-cristallin

et la cristallinité peut être améliorée en recristallisant dans le dichlorométhane

contenant 10% d’alcool benzylique. Par contre, avec un monomère flexible de

configuration cis, la cristallisation est complètement inhibée même en recristallisant

par solvant. Les copolymères cis seraient très utiles pour la fabrication de membranes

pour la filtration où l’on note souvent un vieillissement des membranes par

cristallisation, matérialisé par des craquelures ou des fissures au niveau de la surface.

Les copolymères obtenus par polycondensation ont permis de confirmer la

configuration trans des copolymères obtenus par ADMET par comparaison des

spectres RMN. La cristallisation a été confirmé par diffraction des rayons X et

analyse enthalpique différentielle.

Avec la polycondensation, il est possible, non seulement d’introduire les doubles

liaisons dans les chaînes du polymère de façon parfaitement alternée comme dans le

cas de l’ADMET mais, également de façon aléatoire et à des ratios bloc

rigide/segment flexible modulables, ce qui est impossible de pouvoir se faire avec

l’ADMET. L’insertion du segment flexible de façon alternée dans les chaînes du

polymère a entraîné une baisse des températures de transition vitreuse (Tg) du

copolymère résultant. Ces Tg ont pu être améliorées par modulation du ratio bloc

rigide/segment flexible en utilisant une polycondensation en un seul pot.

Le fait de pouvoir moduler le rapport bloc rigide/segment flexible dans les chaînes du

polymère est un aspect intéressant car il nous donne la possibilité de pouvoir

contrôler les propriétés thermiques, notamment les températures de transition vitreuse

de ces matériaux. Nous avons ainsi montré qu’il est possible d’adapter les propriétés

thermiques de ces matériaux à des applications bien définies.

La spectrométrie de masse MALDI-TOF a permis de montrer que les copolymères

obtenus par variation du ratio bloc rigide/segment flexible sont de nature aléatoire et

non des copolymères blocs, ceci a été confirmé par DSC.

Nous avons également montré qu’il est facile de fonctionnaliser les copolymères par

des réactions thiol-ène clic pour orienter les propriétés vers des applications

147

spécifiques. Des chaînes hydrophiles sont greffées sur les doubles liaisons et les

mesures d’angles de contact ont montré qu’il est possible de contrôler l’hydrophilicité

de ces copolymères. Ce résultat est très important pour l'avenir des membranes à base

de PES, l’enjeu principal consistant à les rendre plus hydrophiles pour réduire le

colmatage lors des processus de filtration de certaines substances telles que les

protéines et, ainsi augmenter leur durée de vie.

Nous aimerions donner quelques recommandations sous forme de pistes

d’exploration pour la poursuite de ces travaux.

- Nous avons synthétisé des copolymères de hautes masses molaires capables de

former des membranes par inversion de phase mais nous n’avons pas pu faire des

essais de filtration, il serait souhaitable d’effectuer des tests de filtration avec ces

copolymères et de voir leur comportement.

- Les résultats de nos travaux ouvrent des perspectives intéressantes pour

l’utilisation des PES comme membrane échangeuse d’ion pour les piles à

combustible. Les PES dont des groupements sulfones sont rajoutés sur les cycles

aromatiques ont été proposés comme membranes échangeuses d’ions dans certaines

piles à combustible.3,4 Cependant, la sulfonation doit se faire localement et avec un

taux élevé d’unités sulfonées pour avoir une bonne séparation de phase, ce qui n’est

pas facile à obtenir. La séparation de phase permet d’avoir une bonne conductivité

protonique et de faibles coefficients de diffusion de la membrane.3,5 Dans le cas des

PES sulfonés, la séparation de phase provient de la différence de polarité entre les

unités hautement sulfonées et les parties hydrophobes du polymère (noyaux

aromatiques).4 Cependant, il est rapporté dans la littérature que des polymères avec

des groupements acides sulfoniques pendants (chaînes latérales) sont plus stables à

l'hydrolyse que ceux avec des fonctions acides sulfoniques directement connectées

sur le squelette des polymères.4

Il serait donc intéressant de greffer, sous forme de chaînes latérales, des chaînes

alkyles terminées par des groupements acides sulfoniques ou des chaînes alkyles

terminées par des fonctions ammonium. Ceci serait possible par les réactions thiol-

148

ène clic si l’autre extrémité de la molécule à greffer est terminée par une fonction

thiol. Les groupements acides sulfoniques et ammoniums serviront à la conductivité

protonique. Les chaînes alkyles devront être assez longues pour permettre une bonne

séparation de phase, et une optimisation sera à prévoir afin que la transition vitreuse

reste acceptable pour l’application visée.

149

5.1 Références


2. Wagener, K. B.; Brzezinska, K.; Anderson, J. D.; Younkin, T. R.; Steppe, K.;

DeBoer, W. Macromolecules 1997, 30, 7363.



5. Guo, Q.; N. Pintauro, P.; Tang, H.; O'Connor, S. J. Membr. Sci. 1999, 154, 175.

150

Annexes

Chapitre 2: Crystallization control of etherethersulfone copolymers by

regular insertion of an allyl functionality

Table A.2.1: Comparison of diffraction peak position for PES and polymers

synthesized in the present work

2θ

(º)

d

(Å)

PES

Form I *

PES

Form II*

PA-4EES

PTA-4AEES

Form I

PA-4EES

After

partial

melting

PAH-4EES PTA-8EES PAH-8EES

9.15 9.67 - - - - - w w

10.6 8.31 - - - - w - -

11.9 7.44 - - w - - w w

12.2 7.28 - - - - w - -

14.0 6.33 - w - - - - -

14.9 5.96 - - - - - w w

15.3 5.81 - - - - m - -

15.6 5.68 - - - - - - -

16.5 5.37 - sh m sh m - -

17.4 5.10 - - m s - vs vs

18.0 4.92 w m - - - - -

18.4 4.82 - - - - -

18.7 4.76 - - - - s - -

151

19.2 4.63 - - m s - vs vs

19.8 4.49 s - - - M - -

20.7 4.29 - s - - - sh sh

21.1 4.20 - - sh m - - -

21.9 3.96 - - s m - - -

22.5 3.96 - - - - M - -

22.8 3.90 m - - - - - -

23.4 3.80 - - - - - s s

23.7 3.76 - - - - m - -

24.5 3.63 m w m m - - -

25.8 3.45 - - - - m - -

26.5 3.36 s w - - - - -

27.8 3.21 - - m - m - -

28.8 3.10 - vw - - - w w

29.0 3.08 - - w w - - -

29.5 3.03 w - - - - - -

31.3 2.86 - - w - - - -

32.0 2.80 - - - - - - w

33.8 2.65 - - - - - - w

34.3 2.62 - - w - - - -

152

35.6 2.52 - - - - w - -

36.5 2.46 - - w - - - -

37.6 2.39 - - - - - w w

39.7 2.27 - - - - w - -

42.8 2.11 - - - - - w w

44.3 2.10 - - w w - - -

44.1 2.05 - - - - w - -

vs = very strong, s = strong, m = medium, w = weak, vw = very weak, sh = shoulder.

*Form I and Form II as reported by Blackadder and coworkers (Blackadder, D. A.;

Ghavamikia, H.; Windle, A. H. Polymer 1979, 20, 781)

153

Figure A.2.1: NMR spectra of 4,4’-bis(4-methoxyphenoxy) diphenyl sulfone

(MPDS) in CDCl3

154

Figure A.2.2: NMR spectra of 4,4’-bis(4-hydroxyphenoxy) diphenyl sulfone (HPDS)

in DMSO

155

Figure A.2.3: NMR spectra of 4,4’-bis(4-allyloxyphenoxy) diphenyl sulfone (APDS)

in CDCl3

156

a)

b)

Figure A.2.4: 1H-NMR spectrum of a) (Z)-1,4-dichlorobut-2-ene in CDCl3 and b)

(E)-1,4-dichlorobut-2-ene in CDCl3

157

Figure A.2.5: NMR spectra of 4-fluoro-4’-hydroxy diphenyl sulfone (FHDS)

158

Figure A.2.6: NMR spectra of 4-fluoro-4’-methoxy diphenyl sulfone (FMDS)

159


methoxyphenylsulfonyl)phenoxy)phenoxy) diphenyl sulfone (MPSPPDS) in CDCl3

160


hydroxyphenylsulfonyl)phenoxy)phenoxy) diphenyl sulfone (HPSPPDS) in DMSO

161

Figure A.2.9: 1H-NMR spectrum of poly(allyl-co-ether ether sulfone ether) (PA-

4EES) in CDCl3

a) Mn = 3300 g/mol

b) Mn = 6200 g/mol

162

163

164

165

Figure A.2.10: 1H-NMR of the 4-ring polymers obtained by polycondensation

a) Poly(trans-allyl-co-ether ether sulfone ether) (PCA-4EES)

b) Poly(cis-allyl-co-ether ether sulfone ether) (PTA-4EES)

c) Poly(hydrogenated allyl-co-ether ether sulfone ether) (PAH-4EES)

d) Poly(chlorinated allyl-co-ether ether sulfone ether) (PACl-4EES)

e) Poly(brominated allyl-co-ether ether sulfone ether) (PABr-4EES)

f) Poly(trans-allyl-co-ether ether sulfone ester) (PAE-4EES)

166

Figure A.2.11: Comparison of PTA-4EES NMR spectra before and after heating,

showing the persistence of the trans signals

a) Before heating

b) After heating

b)

167

M1 = 41 g/mol

M2 = 432 g/mol

M3 = 54 g/mol

If n is the number of M2 repeating units

Mn = 2*M1 + n*M2 + (n-1)*M3

Mn = 2*41 g/mol + n*432 g/mol + (n-1)*54 g/mol

Mn = n*486 g/mol + 28 g/mol

where n is determined by the intensity ratio of the 4.54 ppm polymer peak(e) to that

of the 4.58 ppm peak of the end-group (eEG) proton (e and eEG defined in Figure

A.2.9).

Schéma A.2.1: Mn calculation by NMR

168

Chapitre 3: Synthesis of High Molecular Weight Polyetherethersulfone

- Allyl Copolymers of Controlled glass transition


4EEScb), ratio 50/50



169





170

Chapitre 4: Postfunctionalization by thiol-ene click reactions of

polyetherethersulfone-allyl copolymers for applications in membrane

filtration

Figure A.4.1: NMR spectra of S-2-(2-(2-hydroxyethoxy)ethoxy)ethyl thioacetate in

CDCl3

171

Figure A.4.2: NMR spectra of 2-(2-(2-hydroxyethoxy)ethoxy)ethanethiol in CDCl3

172

a)

b)

Figure A.4.3: FTIR spectra of Poly(6EES-ran-4EEScb) and Poly(6EES-ran-

4EEScb)-graft-C8 a) from 700 to 1900 cm-1 and b) from 2500 to 4000 cm-1

173

Figure A.4.4: 1H-NMR spectra of Poly(6EES-ran-4EEScb) and Poly(6EES-ran-

4EEScb)-graft-C8

174

a)

b)

Figure A.4.5: FTIR spectra of Poly(4EES-alt-cb) and Poly(4EES-alt-cb)-crosslink-Pr

a) from 700 to 1900 cm-1 and b) from 2500 to 4000 cm-1

175

a)

b)


PEG2 a) from 700 to 1900 cm-1 and b) from 2500 to 4000 cm-1

176

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Copolyéthersulfones rigides-flexibles : Modulation des propriétés … · 2018-04-25 · vi 2.2.3.4 Synthesis of 4-fluoro-4-hydroxy diphenyl sulfone (FHDS) (Scheme 2.1b) . 442.2.3.5