Ps

MI

a

ARRAA

KOPDSN

1

acr[aopmds

dhb

0h

Progress in Organic Coatings 77 (2014) 880–891

Contents lists available at ScienceDirect

Progress in Organic Coatings

j o ur nal ho me pag e: www.elsev ier .com/ locate /porgcoat

olymerization of hybrid organic–inorganic materials from severalilicon compounds followed by TGA/DTA, FTIR and NMR techniques

. Criado ∗, I. Sobrados, J. Sanznstituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Inés de la Cruz 3, Cantoblanco, 28049 Madrid, Spain

r t i c l e i n f o

rticle history:eceived 20 February 2013eceived in revised form 17 January 2014ccepted 20 January 2014vailable online 12 February 2014

eywords:rganic–inorganic hybridsolymerizationimensionalityol–gel synthesis

a b s t r a c t

Hybrid organic–inorganic films have been prepared by hydrolysis and condensation of several sili-con compounds: 3-methacryloxypropyltrimethoxysilane (MPTS) or methyltriethoxysilane (MTES) andtetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS) precursors using four [TEOS] or[TMOS]/[MPTS] or [MTES] molar ratios: 0, 0.5, 1 and 2.

The progress on the organic and inorganic polymerizations was followed employing thermogravimetricanalysis (TGA), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), 13Cand 29Si nuclear magnetic resonance (NMR). These techniques have provided information about thehybrid network formation inside films. The formation of the hybrids prepared from [TEOS]/[MPTS] and[TMOS]/[MPTS] mixtures was accomplished through the reaction of Si OR groups, via condensation ofsilanols (inorganic condensation), and opening of the C C double bond in MPTS (organic polymerization).

MR The formation of the hybrids prepared from [TEOS]/[MTES] and [TMOS]/[MTES] mixtures was mainlyaccomplished through the reaction of Si OR groups.

The increment of TEOS or TMOS in MPTS mixtures favored the inorganic (Q3 and Q4 units) condensation.Total degrees of condensation for hybrids synthetized with [TEOS] or [TMOS]/[MTES] were higher thanthose obtained with [TEOS] or [TMOS]/[MPTS], so MTES favored the formation of hybrids with branchedorganic structures.

© 2014 Elsevier B.V. All rights reserved.

. Introduction

The study of hybrid organic–inorganic Si polymers is a veryctive field of the sol–gel process [1]. The importance of theseompounds derives from the possibility of obtaining novel mate-ials in optics, electronics, mechanics and electrochemistry fields2]. One of the most diffused commercial application is their uses coating films [3–6]. These hybrid films combine properties ofrganic polymers and ceramics materials [7]. The inorganic com-onents improve durability, scratch resistance, and adhesion to theetal substrates, while the organic components increase flexibility,

ensity, and functional compatibility with organic polymer paintystems [8].

The sol–gel process is mainly based on hydrolysis and con-

ensation reactions of metal alkoxides (M(OR)n). During theydrolysis (first stage), the replacement of alkoxide groups ( OR)y hydroxyl groups ( OH) occurs during interaction of alkoxide

∗ Corresponding author. Tel.: +34 91 334 9000; fax: +34 91 372 0623.E-mail addresses: mcriado@icmm.csic.es, mcriado@cenim.csic.es (M. Criado).

300-9440/$ – see front matter © 2014 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.porgcoat.2014.01.019

molecules with water. The second stage consists on the conden-sation of two OH groups or of a OH with a OR group, whichproduces M O M bonds [9]. The resulting oxide materials varyfrom nanoparticulate sols to continuous polymer gels depending onthe rate of reactions and drying and processing steps. The hybridorganic–inorganic sol–gel materials can be constituted by stableorganic and inorganic groups linked by stable chemical bonds or byorganic components embedded into an inorganic material, or viceversa [9].

Following the classification of Sanchez et al. [1], hybrids of classII are those exhibiting covalent bonding between organic and inor-ganic components. The organic groups can be directly connectedto the inorganic network and their role can behave as networkmodifiers. A peculiar group of class II hybrids is characterized bythe presence of polymerizable vinyl, acrylate, or epoxy groups.They can be partially or completely polymerized directly in the soldepending on synthesis conditions and photo or thermal curing[10].

The polymerization of organic and inorganic precursors maybe carried out sequentially or simultaneously [11,12]. When theorganic polymerization is performed first, linear polymers orcopolymers are formed, which are functionalized with inorganic

rganic

pasigo

ict

hctrc

2

tSMTSE

mo5taw(p[

fd

Q11

tafiK

rwTmdecmewtsan

M. Criado et al. / Progress in O

olymer precursors, present either in the polymer backbone ort chain ends [13,14]. When the inorganic polymerization is firsttarted in the sol stage, the coating is formed and both organic andnorganic polymerizations are produced in the coated material. Ineneral, it is difficult to achieve high conversion degrees in bothrganic and inorganic networks.

The final physicochemical properties of the hybrid organic–norganic materials depend on the extent of the hydrolysis–ondensation reactions, the branching degree of the polymers andhe gel homogeneity [15].

The aim of this study was to investigate the local structure ofybrid polysiloxane materials prepared from polymerization of Siompounds containing different alkoxide groups. This will permithe future design of new metal coatings that enhance stability ofeinforced concrete structures (RCS) against corrosion caused byhloride ions or carbon dioxide.

. Experimental

The reagents used in this work 3-methacryloxypropyl-rimethoxysilane (CH2 = C(CH3)COO(CH2)3Si(OCH3)3, MPTS,igma–Aldrich), methyltriethoxysilane ((CH3)Si(OCH2CH3)3,TES, Sigma–Aldrich), tetraethyl orthosilicate (Si(OCH2CH3)4,

EOS, Sigma–Aldrich), tetramethyl orthosilicate (Si(OCH3)4, TMOS,igma–Aldrich) and benzoyl peroxide (BPO, VWR Internationalurolab) were laboratory grade.

Sol–gel coatings were prepared from condensation and poly-erization of TEOS and MPTS, TEOS and MTES, TMOS and MPTS

r TMOS and MTES. Sol–gel reactions were achieved by mixing g of MPTS or MTES with the TEOS or TMOS amounts requiredo obtain the four molar ratios: 0, 0.5, 1 and 2. Afterwards, HNO3-cidified water (pH = 1 and [H2O]/[Si] = 3.5) was added. All reagentsere stirred (700 rpm) for 1 h at 60 ◦C, using ethanol as solvent

[ethanol]/[H2O] = 1). At the same time, the thermal initiator ofolymerization (BPO) was added to the mixtures ([BPO]/[MPTS] orMTES] = 0.01).

The films were prepared by drying sols in a Petri dish at 65 ◦Cor 24 h. After curing at 160 ◦C for 3 h, films were detached from theish and analyzed by TGA/DTA, FTIR and MAS-NMR techniques.

The TGA/DTA curves of hybrid films were recorded using a SDT600 TA Instruments, with nitrogen as purge gas at a flow rate of00 ml min−1. Samples were heated from 25 to 600 ◦C at a rate of0 ◦C min−1.

FTIR spectra (4000–250 cm−1) were recorded in two spec-rophotometers: a Nicolet 20 SXC for liquid samples (pure reagents)nd a Bruker IFS 66V/S was used for solid samples (synthetizedlms). In both apparatus the spectral resolution was 2 cm−1. TheBr pellet method was used to prepare solid samples.

Solid-state 29Si MAS and 13C CPMAS-NMR spectra wereecorded using a Bruker Avance-400 pulse spectrometer. Spectraere recorded after irradiation of samples with a �/2 (5-�s) pulse.

he resonance frequencies used were 79.5 and 100.63 MHz (9.4 Tagnetic field). In order to avoid saturation effects, the recycle

elay time used was 10 s. The spinning rate used in MAS-NMRxperiments was 10 kHz. A contact time of 2 ms and a recy-le delay of 5 s were used in 13C CPMAS-NMR experiments. Alleasurements were taken at room temperature with TMS (tetram-

thylsilane) as external standard. The error in chemical shift valuesas estimated to be lower than 0.5 ppm. NMR spectra deconvolu-

ions were performed by using the DMFIT software [16]. Chemicalhift (position of the line), intensity (integrated area), width (widtht half height) and line shape (Lorentzian or Gaussian) of compo-ents were deduced.

Coatings 77 (2014) 880–891 881

3. Results and discussion

3.1. TGA/DTA analysis of the films

In order to understand the thermal behavior of the hybridorganic–inorganic materials, thermogravimetric (TGA) and differ-ential thermal analysis (DTA) were carried out.

The TGA curves of Fig. 1a indicate the existence of three differ-ent weight losses. The first loss, visible in the temperature range25–125 ◦C (was comprised between 1.3 and 1.9%), was associ-ated with evaporation of solvent, specifically ethanol and/or water[17]. The sample mass remained essentially invariable until 300 ◦C.Above this temperature, a second degradation was detected withweight losses of 40.5, 31.5, 27.7 and 20.0% for R0, R0.5, R1 and R2ratios, respectively. This second step can be attributed to randomscissions within the polymer chains [6,18]. The last loss took placefrom 470 ◦C to 600 ◦C, displaying 16.8, 14.7, 13.8 and 12.0% weightlosses for R0, R0.5, R1 and R2 ratios, respectively. This loss wasattributed to the dehydration of silanol groups present in the SiO2network [18].

The DTA curves of Fig. 1b show three minima at about 47–63 ◦C,386–402 ◦C and 479–550 ◦C, attributed to three detected stages.The three weight losses presented an endothermic character.Finally, two other minima were observed in R0, R1 samples at about340–350 ◦C, that were ascribed to scissions of chains produced atthe terminal vinylidene groups [6,18].

The TGA curves of Fig. 1c show a small weight loss (0.13–4.46%)below 160 ◦C, assigned to the evaporation of residual smallmolecules, such as water, alcohol, and ethanol [17]. The amount ofwater and ethanol lost in this series of hybrids is higher than thatadded in the synthesis hybrids formed from TEOS and MPTS. In thetemperature range 160–440 ◦C (minimum peak around 340 ◦C inabsence of TEOS and around 240 ◦C in presence of TEOS), a newdegradation was observed, see Fig. 1c. This could be assigned tovolatile compounds produced in condensation of Si OH and Si ORgroups [19]. The weight loss was between 3.2 and 5.1%. The last lossshould result from the oxidation and degradation of methyl groupsof MTES, that probably cause the formation of Si C Si bonds at536 ◦C [20,21]. The associated weight loss was between 2.6 and5.6%.

DTA curves of Fig. 1d shows three minima between 38–62 ◦C(first stage), 229–339 ◦C (second stage) and 527–548 ◦C (thirdstage). The three peaks display an endothermic character. As the[TEOS]/[MTES] ratios and temperatures increases, suggesting ahigher thermal stability of formed hybrids.

Thermograms of the hybrid polysiloxanes synthetized fromTMOS and MPTS (see Fig. 2a) are very similar to those obtainedfor hybrid polysiloxanes prepared by mixing TEOS and MPTS (seeFig. 1a). In these thermograms, three degradation stages weredetected; the first visible below 110 ◦C, due to the evaporation ofethanol and water [17], with weight losses between 1.3 and 1.5%.The second stage, produced between 110 ◦C and 470 ◦C, attributedto scission within the polymer chains [6,18], with weight losses of40.5, 31.5, 26.4 and 19.5% for R0, R0.5, R1 and R2. Finally, the thirdstage produced between 470 and 600 ◦C, ascribed to the dehydra-tion of silanol groups present in SiO2 networks [18], with weightlosses between 13.1 and 16.8%. The DTA curves of this family ofhybrids (see Fig. 2b) are also similar to those obtained for the hybridpolysiloxanes synthetized from TEOS and MPTS (see Fig. 1b), whichpresented three minima at 47–50 ◦C, 390–402 ◦C and 479–527 ◦Cfor three weight losses. Finally it should be highlighted the pres-ence of an additional endothermic peak between 197 and 209 ◦C

for R1 and R2 ratios, associated to the scissions of head-to-headlinkages in the polymethylmethacrylate homopolymer [18].

The temperatures corresponding to each degradation stagewere similar for the hybrid polysiloxanes synthetized from TEOS

882 M. Criado et al. / Progress in Organic Coatings 77 (2014) 880–891

600500400300200100-1,5

-1,0

-0,5

0,0

0,5

1,0

1,5

Tem

pera

ture

Diff

eren

ce (0 C

)

Temperatur e (0C)

R0R0.5R1R2

(b)

600500400300200100070

80

90

100

R0R0.5R1R2

Wei

ght l

oss

(%)

Temperature (0C)

(c)

600500400300200100020

40

60

80

100

R0R0.5R1R2

Wei

ght l

oss

(%)

Temperature (0C)

(a)

600500400300200100

-1,6

-1,2

-0,8

-0,4

0,0

0,4

0,8

1,2

Tem

pera

ture

Diff

eren

ce/ 0 C

Temperature (0C)

R0R0.5R1R2

(d)

F PTS](

at[FS1

Mpdawdcwtda

fF4isdi

ig. 1. TGA and DTA curves of the hybrid polysiloxanes synthetized with [TEOS]/[MR1) and 2 (R2).

nd MPTS and TMOS and MPTS. However, it must be remarkedhat, the organic polymerization through C C bond was favored inTEOS]/[MPTS] system (minimum at 340–350 ◦C in the DTA curves,ig. 1b), while the organic polymerization took place through theiOR groups ( CH2Si(OR)3) in [TMOS]/[MPTS] system (peak at97–209 ◦C in the DTA curves, Fig. 2b).

The TGA curves of the hybrids synthetized from TMOS andTES (see Fig. 2c) are very similar to those obtained for hybrids

repared by mixing TEOS and MTES (see Fig. 1c). Three degra-ation stages were detected in these thermograms. The first wasssigned to the evaporation of water and ethanol again; witheight losses below 160 ◦C of the order 0.1–5.0%. The second degra-ation stage was attributed to volatile compounds produced inondensation of Si OH and Si OR groups [19], at 160–435 ◦C, witheight losses between 3.2 and 4.2%. The third stage associated to

he oxidation and degradation of methyl groups of MTES was pro-uced between 435 and 600 ◦C. This weigh loss was between 2.6nd 4.5%.

The DTA curves of Fig. 2d are also similar that those obtainedor the hybrid polysiloxanes synthetized from TEOS and MTES (seeig. 1d), which presented three minima at 38–69 ◦C, 248–329 ◦C and62–527 ◦C for three weight losses. As the [TMOS]/[MTES] ratios

ncreases, the temperature decreases, suggesting a lower thermaltability of formed hybrids. This behavior was opposite to thatepicted by polysiloxanes synthetized from TEOS and MTES. The

ncrease in the amount of TEOS and TMOS favored the inorganic

(a and b) and with [TEOS]/[MTES] (c and d) in molar ratios of: 0 (R0), 0.5 (R0.5), 1

condensation, but TEOS favored the formation of a more stablecross-linked structure.

The temperatures corresponding to second degradation step,attributed to the scissions within the polymer chains, were differ-ent. The temperatures for [TEOS]/[MTES] system were lower thanthose for [TMOS]/[MTES] system. This different behavior may bedue to the formation of a hybrid organic–inorganic network, whereorganic polymerization process is more favored than the formationof the silica backbone [6].

3.2. FTIR characterization of the films

Fig. 3 shows the FTIR spectra of four reagents used in reactions:(a) 3-methacryloxypropyltrimethoxysilane (MPTS), (b) methyltri-ethoxysilane (MTES), (c) tetraethyl orthosilicate (TEOS) and (d)tetramethyl orthosilicate (TMOS). The assignment of the differentvibration bands is given in four tables (supplementary data).

Fig. 3a shows the characteristic vibration bands of MPTS. Thoseat 1703 and 1323 cm−1 (signals 5 and 9) were assigned to theasymmetric stretching of the C O bond and vibrations of ester C( O) O groups [22,23]. The band around 1635 cm−1 (signal 6) wasassociated with vinyl groups [22,23]. The band at 1299 cm−1 (signal

10) was assigned to Si C bonds [22,23]. This spectrum also showsthree vibrations corresponding to Si O C bonds: 1174, 1099 and1029 cm−1 (signals 11, 12 and 13) [24]. Finally, two bands detectedat 3671 and 919 cm−1 (signals 1 and 14) were assigned to the

M. Criado et al. / Progress in Organic Coatings 77 (2014) 880–891 883

600500400300200100020

40

60

80

100

R0R0.5R1R2

Wei

ght l

oss

(%)

Temperature (0C)

(a)

600500400300200100-1,5

-1,0

-0,5

0,0

0,5

1,0

1,5

Tem

pera

ture

Diff

eren

ce (0 C

)

Temperature (0C)

R0R0.5R1R2

(b)

600500400300200100

-1,6

-1,2

-0,8

-0,4

0,0

0,4

0,8

1,2

Tem

pera

ture

Diff

eren

ce/ 0 C

Temperature (0C)

R0R0.5R1R2

(d)

600500400300200100070

80

90

100

R0R0.5R1R2

Wei

ght l

oss

(%)

Temperature (0C)

(c)

F PTS](

vo

saS(b

s1Fa

o6Sb

wf[

mio

ig. 2. TGA and DTA curves of the hybrid polysiloxanes synthetized with [TMOS]/[MR1) and 2 (R2).

ibrations of silanol (SiOH) [25], probably produced by hydrolysisf MPTS in contact with the atmosphere.

Infrared spectrum of methyltriethoxysilane (MTES) (see Fig. 3b)hows bending bands of Si C bonds at 1265 and 781 cm−1 (signals 5nd 11) [22,23]. There are also five characteristics vibration bands ofi O C bonds at 1158, 1107 and 1074 (doublet), 995 and 815 cm−1

signals 6, 7, 8, 9 and 10) [24,26], and the bending band of O Si Oonds at low wavenumbers (443 cm−1, signal 12) [26].

Infrared spectrum of tetraethyl orthosilicate (TEOS) (see Fig. 3c),hows five vibration bands of Si O C bonds at 1170, 1102 and079 (doublet), 961 and 787 cm−1 (signals 6, 7, 8, 9 and 10) [24].inally, the bending band of O C C bonds (signal 11) was detectedt 477 cm−1 [27].

Fig. 3d shows the characteristic vibration bands of tetramethylrthosilicate (TMOS) at 1198, 1092, 829 and 426 cm−1 (signals 5,, 7 and 8). The first three bands were associated with stretchingi O C bands and the latter corresponded to the bending O Si Oands [24,26].

After the characterization of the reagents, the FTIR studyas conducted in hybrid polysiloxanes synthetized via sol–gel

rom mixtures of various reagents: [TEOS]/[MPTS], [TEOS]/[MTES],TMOS]/[MPTS] and [TMOS]/[MTES] (Fig. 4).

In general, mixtures of [TEOS]/[MPTS] and [TMOS]/[MPTS] pro-ote thermal curing condensation of inorganic structures and also

nduced the formation of an organic polymer interconnected bypening double C C bond of MPTS.

(a and b) and with [TMOS]/[MTES] (c and d) in molar ratios of: 0 (R0), 0.5 (R0.5), 1

To follow the organic polymerization of the materials, the anal-ysis was focused on 1730 and 1635 cm−1 bands (signals 3 and 4)assigned to C O and C C vibration modes, see Fig. 4a and c. Adecrease in the intensity of the C C band (1635 cm−1) when addinga larger amount of TMOS or TEOS, indicated that the organic poly-merization have occurred. This reaction was accompanied by thedecrease and broadening of the C O band, produced by openingof C C bonds as the polymerization increased, independently of[TEOS]/[MPTS] and [TMOS]/[MPTS] ratios employed. The observedbroadening of the carbonyl group band should be associated withthe presence of two vibration modes at 1703 cm−1, assigned tothe stretching vibrations of C O conjugated with C C bonds, andanother mode at 1730 cm−1 assigned to the stretching vibrationsof C O, produced during the organic polymerization [12,28]. Thepresence of the 1730 cm−1 band confirmed the polymerizationreaction in films. In Fig. 4a and c, it was observed that the inten-sity of this band decreased with the increasing amount of TEOS andTMOS. This modification may be due to the competition betweenthe organic and inorganic polymerization in the formation of hybridmaterials. If the growth of the organic chains happens when theinorganic network is already formed, the mobility of the organicgroups is dramatically hindered and there is not enough free space

in the rigid framework to reach a larger degree of polymerization.

On the other hand, the formation of a connected silica back-bone was accomplished not only through the reaction of Si ORgroups but also via the condensation of silanols. The condensation

884 M. Criado et al. / Progress in Organic Coatings 77 (2014) 880–891

5001000150020002500300035004000

2

Wavenumber (cm-1)

(b)

1

12

3 114

105

96

87

5001000150020002500300035004000

11

10

8

Wavenumber (cm-1)

(c)

9

5

4

2

31

6

7

5001000150020002500300035004000

143

2

Wavenumber (cm-1)

(a)

1 64

5

13

7

11129108

5001000150020002500300035004000

8

7

6

5

4

32

Wavenumber (cm-1)

(d)

1

ed: (a

oa(iotw(rwou(

tasrocica1w

Fig. 3. FTIR spectra of four reagents studi

f silanols was confirmed by IR spectroscopy (Fig. 4a and c), where variation on the intensities and the wavenumber of SiOH bands3671 and 919 cm−1) was detected along the reaction. The stretch-ng Si OH band of pure MPTS was detected at 3671 cm−1 (silanolsn the gel surface [25]). When this reagent was subjected tohermal treatments (R0 molar ratio), this band shifted to loweravenumbers (3504 cm−1, signal 1) indicating that silanols reacted

Fig. 4a and c). In IR spectra of materials with R0.5, R1 and R2 molaratios, the band at 3495 cm−1 (signal 2) was ascribed to adsorbedater [25], see Fig. 4a and c. By increasing the amount of TMOS

r TEOS, the intensity of the 919 cm−1 band (signal 8) decreasedntil disappearing and a new band was detected around 940 cm−1

signal 9), associated with vibrations of the Si O Si bonds.Inorganic condensation reactions of polysiloxanes also occurred

hrough the reaction of Si OR groups, producing a series of bandsround 1167, 1122 and 1060 cm−1 (signals 5, 6 and 7) which corre-ponded to both Si O Si and Si O C bonds for R0 and R0.5 molaratios (see Fig. 4a and c). Increasing the amount of TMOS or TEOSnly two bands were detected at 1169 and 1054 cm−1 (asymmetri-al stretching of Si O Si bonds). The intensity of 1054 cm−1 bandncreased with the addition of TMOS or TEOS, confirming inorganic

ondensation reactions. These reactions were corroborated by theppearance of two new bands at 692 and 600 cm−1 (signals 10 and1) probably due to O Si O ring siloxanes vibrations [25], whichere not observed in pure reagents.

) MPTS, (b) MTES, (c) TEOS and (d) TMOS.

Fig. 4b and d shows the FTIR spectra of hybrid materialsobtained in TEOS/MTES and TMOS/MTES mixtures. In these cases,the inorganic condensation reactions occurred mainly throughSi OR groups. The spectra show Si O Si asymmetric stretchingvibrations (1130 and 1028 cm−1, signals 2 and 3), which wereshifted slightly to higher wavelength values while adding moreTMOS or TEOS to the mixture (1148 and 1059 cm−1). The intensityof the band at 1059 cm−1 increases confirming the strengtheningof the siloxane network. This fact was confirmed by the appear-ance of two new bands, different to those found in pure reagents(see Fig. 4b and d); the first detected at 947 cm−1 (signal 4), asso-ciated with the vibration modes of Si O Si bonds, and the secondat 579 cm−1 (signal 6), associated to vibration modes of O Si Obonds in cyclic siloxanes structures [25].

Fig. 4b and d shows a decrease in the intensity of the bandsat 1277 and 785–774 cm−1 (doublet) (signals 1 and 5), ascribedto vibrations of Si C bonds, indicative of a lower proportionof these groups in the polysiloxane structure. The condensa-tion reactions increased the number of Si O Si bonds in hybridmaterials.

3.3. NMR-MAS characterization of the films

29Si spectra show one signal for each of the reactants (seeFig. 5a). Chemical shift of MPTS and MTES signals, assigned to

M. Criado et al. / Progress in Organic Coatings 77 (2014) 880–891 885

5001000150020002500300035004000

R2

R1

R0.5

R0

6

4

532

Numero de on da (cm-1)

1

(b)

5001000150020002500300035004000

R2

R1

R0.5

R0

8

9

11

104 7

653

2

Wavenumber (cm-1)

1

(c)

5001000150020002500300035004000

R2

R1

R0.5

10

11

9

7

6

8

5

4

3

2

Wavenumber (cm-1)

1

(a)

R0

5001000150020002500300035004000

R2

R1

R0.5

R0

4

5

6

32

Wavenumber (cm-1)

1

(d)

Fig. 4. FTIR spectra of the hybrid polysiloxanes prepared with mixtures of the following reagents: (a) [TEOS]/[MPTS] (b) [TEOS]/[MTES] (c) [TMOS]/[MPTS] and (d)[TMOS]/[MTES] in molar ratios of 0 (R0), 0.5 (R0.5), 1 (R1) and 2 (R2).

-140-120-100-80-60-40-20

-82

-79

-44

TMOS

TEOS

MTES

MPTS

Chemical shift (ppm)

(a)

-43

-4004080120160200

10

24135678

911

13 12

TMOS

TEOS

MTES

MPTS

Chemical sh ift (pp m)

(b) 14

Fig. 5. (a) 29Si and (b) 13C MAS-NMR spectra of four pure reagents.

886 M. Criado et al. / Progress in Organic Coatings 77 (2014) 880–891

-4004080120160200

4

8` 7`

7`

6`

8`

12

135

3

R2

R1

R0.5

R0

8 76

2

Chemica l sh ift (ppm )

1

(b)

-4004080120160200

1213 10

9

R2

R1

R0.5

R0

Chemica l shif t ( ppm)

11

(d)

-140-120-100-80-60-40-20

Q2

R2

R1

R0.5

R0

T1

T2

T3Q3

Chemica l shift (ppm)

Q4(a)

-140-120-100-80-60-40-20

Q2

R2

R1

R0.5

R0

T1

T2

T3

Q3

Chemica l shift (ppm)

Q4

(c)

F rom [0

Rwe

Mtg2(v7M1Cs1T(

ig. 6. 29Si MAS and 13C CPMAS-NMR spectra of hybrid polysiloxanes synthetized f.5 (R0.5), 1 (R1) and 2 (R2).

CH2-Si(OR)3 environments, appeared about −43/−44 ppm,hereas the signal of TMOS and TEOS, assigned to Si-(OR)4

nvironments, were between −79 and −82 ppm.Fig. 5b shows 13C CPMAS-NMR spectra of the various reagents.

PTS spectrum consisted of 8 signals, where first carbon linked tohe silicon appear at 5 ppm (signal 1), carbon in the methyl terminalroup at 18 ppm (signal 2), second carbon close to the silicon at2 ppm (signal 3), carbon in the methyl close to oxygen at 50 ppmsignal 4), third carbon close to the silicon at 66 ppm (signal 5),inyl group carbons (CH2 = C) at 124 and 136 ppm (signals 6 and, respectively) and carbonyl group at 166 ppm (signal 8) [28]. InTES spectrum three signals detected at −8, 18, 57 ppm (signals 9,

0 and 11), correspond to CH3 groups directly bonded to silicon,H3 groups attached to CH2 and CH2 groups. The TEOS spectrum

howed two carbon signals: one of CH3 groups (18 ppm, signal2) and other of CH2 groups (58 ppm, signal 13). The spectrum ofMOS was constituted only by a signal of CH3 groups at 50 ppmsignal 14).

TEOS]/[MPTS] (a and b) and from [TEOS]/[MTES] (c and d) in molar ratios of 0 (R0),

29Si spectra corresponding to hybrid polysiloxanes synthetizedfrom [TEOS]/[MPTS] are given in Fig. 6a and b. The spectrum ofFig. 6a, shows three signals at 49, 58 and 67 ppm, assigned toT1 units ( CH2Si(OSi)(OR)2, R = H or CH3), T2 ( CH2Si(OSi)2(OR))and T3 ( CH2Si(OSi)3) [6,12,29], which were related to the con-densation of the organic material. In the absence or presence of asmall amount of TEOS (R0 and R0.5) T2 units predominated, indicat-ing that the hybrids formed were mainly linear siloxane structures.Increasing the amount of TEOS the percentage of T3 units andtherefore the degree of polycondensation increased giving morebranched siloxanes structures.

If attention is focused on the condensation reactions of the inor-ganic part of the hybrid, the 29Si spectra show, in presence of TEOS(R0.5), three additional signals at −91, −101 and −109 ppm, asso-

ciated with Q2 (Si(OSi)2(OR)2), Q3 (Si(OSi)3(OR)) and Q4 (Si(OSi)4)species [6,12,29]. For R1 and R2 ratios, the intensities of Q3 and Q4

units increased considerably, becoming the percentage of Q4 unitssimilar to that of Q3 units.

M. Criado et al. / Progress in Organic Coatings 77 (2014) 880–891 887

-4004080120160200

46`7`8`5 3

R2

R1

R0.5

R0

8 76

2

Chemical shift (ppm)

1

(b)

-4004080120160200

10

9

R2

R1

R0.5

R0

Chemical shift (ppm)

11

(d)

-140-120-100-80-60-40-20

Q2

R2

R1

R0.5

R0

T1T2

T3

Q3

Chemical shift (ppm)

Q4

(a)

-140-120-100-80-60-40-20

Q2

R2

R1

R0.5

R0

T1

T2

T3

Q3

Chemical shift (ppm)

Q4

(c)

F om [T0

Mpcwgfi7stMo

rothh

ig. 7. 29Si MAS and 13C CPMAS-NMR spectra of hybrid polysiloxanes synthetized fr.5 (R0.5), 1 (R1) and 2 (R2).

13C spectra provide information about the polymerization of thePTS methacryloxy groups (see Fig. 6b). These spectra showed the

resence of two signals at 126 and 136 ppm (signals 6 and 7), asso-iated with CH2 = C carbons, and one signal at 167 ppm associatedith carbonyl groups (signal 8) of unpolymerized methacryloxy

roups. The polymerization of the organic part of hybrids was con-rmed by the detection of the quaternary carbon at 45 ppm (signal′), the CH2-groups of polymerized hydrocarbon chains (56 ppm,ignal 6′) and the C O groups located near aliphatic carbons, afterhe C C opening (176 ppm, signal 8′) [28], not detected in pure

PTS. The increment of signals 12 and 13 suggested the presencef a large amount of TEOS in the medium.

Fig. 6c and d shows 29Si and 13C NMR spectra of hybrid mate-ials obtained by mixing MTES and TEOS. 29Si MAS-NMR spectra

f hybrids show three signals at −55, −59 and −66 ppm, assignedo T1, T2 and T3 units (see Fig. 6c). T3 units predominated even inybrids with low ratios, R0 and R0.5, suggesting the formation ofighly branched organic structures. The addition of TEOS promoted

MOS]/[MPTS] (a and b) and from [TMOS]/[MTES] (c and d) in molar ratios of 0 (R0),

the condensation reaction of the inorganic part as seen in the spec-tra of Fig. 6c. In this case, Q2, Q3 and Q4 species (−93, −101 and−109 ppm) were formed whose intensities increased with the TEOScontent.

Fig. 6d shows the 13C NMR spectra of hybrid polysiloxanes withdifferent R ratios. It could be observed in all cases the presence ofthree signals at −4, 18 and 58 ppm, assigned to the carbon bondeddirectly to Si (signal 9), CH3 group (signal 10) and CH2 groups (signal11) of MTES. In this system, the organic condensation could notoccur through the organic vinyl group, since none of the startingreagents presented this organic group. However, it can be seen thatthe intensity of the signals 10 and 11 increased with the additionof TEOS to the system, confirming that these signals correspond tothis reagent (signals 12 and 13, see Fig. 6d).

29Si spectra confirm that the condensation reactions occurredin hybrid materials (see Fig. 7a). If the analysis focused on theorganic polymerization, it could be observed that spectra are ini-tially dominated by T2 units, indicating that polysiloxanes had

8 rganic

lbo

Fdbcm

cMstwwtg

oe−ptr(np

ot1crt

3

r

TT

D

dd

88 M. Criado et al. / Progress in O

inear structures. When adding a larger amount of TMOS, the num-er of T3 units increased, suggesting that the structure of therganic part displays higher connectivity.

With respect to the inorganic condensation, NMR spectra ofig. 7a show that in the absence of TMOS, Qn units were notetected, but in the presence of this reagent, reaction occurredetween TMOS and MPTS, detecting Q2, Q3 and Q4 units. The per-entage of Q3 and Q4 units increased with the amount of TMOS,ainly Q3 units.Through 13C CPMAS-NMR spectra of Fig. 7b it is possible to

heck if the organic condensation reactions is produced throughPTS methacryloxy groups. In this case, signals at 176 ppm (C O,

ignal 8′), 55 ppm ( CH2-carbonyl, signal 6′) and 45 ppm (qua-ernary carbon, signal 7′) should be detected [28]. These signalsere observed in all NMR spectra, but their intensities decreasedith increasing TMOS (R2), indicating that under these condi-

ions organic condensation was not favored via methacryloxyroup.

Fig. 7c and d shows the 29Si MAS and 13C CPMAS-NMR spectraf hybrid materials obtained by mixing TMOS and MTES in differ-nt molar ratios. 29Si spectra show three signals at −55, −59 and66 ppm, assigned to T1, T2 and T3 units. In all cases, T3 units wereredominant and the hybrids formed displayed branched struc-ures. The addition of TMOS favored the inorganic condensationeactions as demonstrated by the presence of Q2, Q3 and Q4 units−92, −100 and −109 ppm), see Fig. 7c. The intensities of these sig-als increased with the addition of TMOS, mainly increasing theercentage of Q3 units.

Finally, Fig. 7d shows the 13C spectra of hybrid materialsbtained with different [TMOS]/[MTES] ratios. In these spectra onlyhree signals were observed corresponding to carbons of MTES (−6,6 and 59 ppm of signals 9, 10 and 11) but any signal associated witharbons of the OCH3 group of TMOS (50 ppm), indicating that thiseagent had reacted with MTES. In this system organic condensa-ion through the vinyl group was not possible.

.4. Organic–inorganic condensation

The local structure of hybrid organic–inorganic materialsesults from organic and inorganic polymerizations, which are not

able 1he degrees of condensation of the T and Q species of the hybrid organic–inorganic syste

Samples Ratios Proportionsa (%) Dc

T1 T2 T3 Q2 Q3 Q4

[TEOS]/[MPTS] 0 11.1 58.6 30.3 – – – 730.5 3.5 37.7 30.3 6.2 13.6 8.7 791 12.0 14.4 27.8 4.5 23.6 17.7 762 9.6 12.2 14.9 4.1 30.9 28.3 71

[TMOS]/[MPTS] 0 11.1 58.6 30.3 – – – 730.5 4.7 40.1 27.3 4.3 15.0 8.6 771 10.1 21.5 25.1 3.6 24.1 15.6 752 14.4 9.5 15.4 5.9 34.7 20.1 67

[TEOS]/[MTES] 0 9.9 14.1 76.0 – – – 880.5 8.8 7.6 50.0 2.2 16.0 15.4 871 7.3 7.4 34.5 4.2 27.2 19.4 852 5.6 5.2 22.8 9.0 37.6 19.8 83

[TMOS]/[MTES] 0 9.9 14.1 76.0 – – – 880.5 7.7 7.7 48.0 2.9 21.7 11.9 871 5.0 5.5 38.2 4.7 29.3 17.3 892 4.5 4.4 23.1 6.4 42.0 19.6 86

a Proportions (%) were calculated by the deconvolution technique. Errors are ±1%.b Ratio (%): Tn = [total T species/(T species + Q species)] × 100%, Qn = [total Q species/(T sc(T) and Dc(Q) are the degrees of condensation of the T and Q species respectively.c Total degree of condensation, TDc(%): (Dc(T) × Tn ratio (%) + Dc(Q) × Qn ratio (%))/100.

(T) = [(T1 + 2T2 + 3T3)/Tn] and d(Q) = [(Q1 + 2Q2 + 3Q3 + 4Q4)/Qn].total = (Tn × d(T) + Qn × d(Q))/(Tn + Qn).

Coatings 77 (2014) 880–891

independent in investigated hybrids. The proportions of Tn and Qn

species, strongly related to the formation of Si O C and Si O Sibonds, can be deduced from 29Si MAS-NMR spectra using a standardGaussian lineshape deconvolution. Qn/Tn ratios were found to bepractically equal to nominal 0, 0.5, 1 and 2 values used in the syn-thesis, confirming the NMR spectral fit goodness.

From deduced values, the degree of condensation of T and Qspecies was calculated from Tn and Qn values, according to expres-sions [30]:

Dc(T) =[

(T1 + 2T2 + 3T3)3

]× 100 (1)

Dc(Q) =[

(Q1 + 2Q2 + 3Q3 + 4Q4)4

]× 100 (2)

where Dc(T) is the degree of condensation of T species, Tn describingthe relative amount of T species; Dc(Q) is the degree of condensa-tion of Q species, Qn describing the relative amount of Q species.Values obtained in these calculations are given in Table 1.

Table 1 Degrees of condensation of T and Q species deduced from29Si MAS-NMR spectra of hybrid organic–inorganic materials.

Regarding the condensation of TEOS or TMOS with MPTS, theevolution of T and Q species, deduced from 29Si MAS-NMR spec-tra, was analyzed. The fits of 29Si spectra for all R2 ratios wererepresented in Figs. 6 and 7; similar fits were obtained for therest of spectra (not shown). T2 units were present in significantconcentrations at low molar ratios (R0 and R0.5) while T3 groupspredominated at R1 ratio (see Table 1). The addition of a higheramount of TEOS or TMOS (R2 ratio) favored the decrease of therelative concentration of T3 groups, making this percentage moresimilar to those of T1 and T2 groups. The presence of T1 groups indi-cated that only part of T species had participated in condensationreactions (see Table 1).

The 29Si MAS-NMR spectra show that hybrid materials aremainly cross-linked by Q3 and Q4 species independently of the

molar ratio employed. In general, the increment of TEOS or TMOSfavored the presence of Q4 groups, in [TEOS]/[MPTS] mixtures.Therefore, the degree of condensation of the Q species increasesas the molar ratio R increases (see Table 1).

ms from the 29Si MAS-NMR spectra.

(T) (%) Dc (Q) (%) Ratiob (%) TDcc (%) d(T) d(Q) dtotal

Tn Qn

.1 0.0 100.0 0.0 73.1 2.19 – 2.19

.2 77.2 71.5 28.5 78.6 2.37 3.09 2.58

.4 82.2 54.2 45.8 79.0 2.29 3.29 2.75

.5 84.5 36.7 63.3 79.7 2.14 3.38 2.93

.1 0.0 100.0 0.0 73.1 2.19 – 2.19

.1 78.9 72.1 27.9 77.6 2.31 3.15 2.55

.5 82.0 56.7 43.3 78.3 2.26 3.28 2.70

.5 80.9 39.3 60.7 75.6 2.02 3.23 2.76

.7 0.0 100.0 0.0 88.7 2.66 – 2.66

.4 84.8 66.4 33.6 86.5 2.62 3.39 2.88

.0 82.5 49.2 50.8 83.8 2.55 3.30 2.93

.7 79.0 33.6 66.4 80.6 2.51 3.16 2.94

.7 0.0 100.0 0.0 88.7 2.66 – 2.66

.9 81.2 63.4 36.6 85.4 2.64 3.25 2.86

.4 81.1 48.7 51.3 85.2 2.68 3.25 2.97

.1 79.8 32.0 68.0 81.8 2.58 3.19 2.99

pecies + Q species)] × 100%.

rganic

dtttpswt[70

tcthcspac

Tssotpa0dhm

dtsotoap8toi

t

TT

C

M. Criado et al. / Progress in O

In light of these results, the total degree of condensationepends on the amount of TEOS or TMOS. A higher amount ofhese reagents (ratio of 1) did not favor the organic polymeriza-ion through C C bonds, because steric hindrance generated byhe high number of side chains. The organic condensation tooklace through SiOR groups ( CH2Si(OR)3) and generated branchedtructures favors T3 species. For R2, the inorganic condensationas favored, the mobility of the organic groups is hindered and

he degree of polymerization decreases. The values obtained forTEOS]/[MPTS] hybrids prepared with ratios of 0.5, 1 and 2 are 79%,9% and 80%. For hybrids prepared with [TMOS]/[MPTS] ratios of.5, 1 and 2, these values were 78%, 78% and 76%.

On the other hand, the evolution of T bands with the condensa-ion of TEOS or TMOS with MTES was similar (see Table 1). In theseases, T3 groups were predominant and relative concentrations ofhese species decreased with the molar ratio. The incorporation of aigher amount of TEOS or TMOS produced a decrease of the organicondensation degree (see Table 1). However, the values of conden-ation degrees were higher than those obtained for hybrid materialsrepared with [TEOS]/[MPTS] or [TMOS]/[MPTS], so the percent-ge of T3 species was significant greater in former ones (degree ofondensation upper 84%).

Regarding the evolution of Q bands with the condensation ofEOS or TMOS with MTES, practically no differences were detected,ee Table 1. These materials were mainly constituted by Q3 and Q4

pecies, the amount of Q3 units increasing with the amount of TEOSr TMOS, while the amount of Q4 groups remains independent ofhe molar ratio. The degree of inorganic condensation of hybridsrepared with [TEOS]/[MTES] ratios 0.5, 1 and 2 was 85%, 82%nd 79% and that of hybrids prepared with [TMOS]/[MTES] ratios.5, 1 and 2 was 81%, 81% and 80% respectively (see Table 1). Theegree of inorganic condensation was similar to that obtained forybrid materials prepared with [TEOS]/[MPTS] or [TMOS]/[MPTS]ixtures (between 79 and 85%).In light of these results, the total degree of condensation is

ependent of the amount of TEOS or TMOS, the incorporation ofhese reagents leading to a decrease of the total degree of conden-ation. The relative amount of T3 species clearly decreased and thatf Q4 species remained practically constant. The heterocondensa-ion reactions are less favored between T and Q units. The valuesbtained for hybrids prepared with [TEOS]/[MTES] ratios of 0.5, 1nd 2 were 86%, 84% and 81% respectively and for hybrids pre-ared with [TMOS]/[MTES] ratios 0.5, 1 and 2 were 85%, 85% and2%. The values of total degree of condensation were higher thanhose obtained for hybrid materials prepared with [TEOS]/[MPTS]r [TMOS]/[MPTS], indicating that the condensation of the species

n former systems was more favored.

On the other hand, MTES had no double C C bonds andhe organic polymerization took place through SiOR groups

able 2he peak areas of the signals in the 13C MAS-NMR spectra of the mixtures [TEOS]/[MPTS]

Samples Ratios

1(9

ppm)

2(18

ppm)

3(22

ppm)

7`(45

ppm)[TE OS]/[MPTS] 0 13.7 12.2 19.0 16.1

0.5 17.3 12.2 17.8 14.1 1 14.6 9.5 22.7 14.4 2 14.2 16.3 18.3 12.5

[TMOS]/[MPTS] 0 13.7 12.2 19.0 16.1 0.5 11.4 8.3 22.7 15.51 13.5 11.7 18.6 13.7 2 12.7 21.7 13.8 4.3

olour emphasized the new signals that are formed when organic polymerization has be

Coatings 77 (2014) 880–891 889

( CH2Si(OR)3), favoring structures with a higher degree of Tpolymerization (T3 groups display important concentrations, seeTable 1).

As it has been previously mentioned, the hybrid network forma-tion is influenced by organic polymerization through methacryloxygroups, which can be monitored by using 13C CPMAS-NMR spec-troscopy. The presence or absence of TEOS and TMOS precursorshad a great influence on the extension of vinyl polymerizationand the utilization of TEOS or TMOS affects in different way thedevelopment of the reaction. Table 2 shows relative intensitiesof species detected in 13C CPMAS-NMR spectra of [TEOS]/[MPTS]and [TMOS]/[MPTS] mixtures. Estimated values should only beconsidered in a semiquantitative way, because cross polarizationefficiency in CPMAS experiments can differs considerably for dif-ferent environments.

In absence of TEOS or TMOS, the relative intensity of the qua-ternary carbons (signal 7′, at 45 ppm), carbons of polymerizedhydrocarbon chain CH2 (signal 6′, 58 ppm) and carbonyl groupsclose to aliphatic carbons, after C C opening (signal 8′, 177 ppm)are 16, 4 and 12% respectively, confirming that the organic poly-merization is produced by C C opening in MPTS. The presence ofTEOS or TMOS (R = 0.5) produced a decrement in the area of 7′ and8′ peaks, indicating the existence of some competition betweenthe vinyl polymerization and the SiOR polymerization through the(R = CH3) (signal 4, at 51 ppm). In the specific case of TEOS, a higheramount of this reagent (R = 1) increased slightly the intensity of7′ and 8′ peaks, supporting the vinyl polymerization. When R = 2,these signals decreased, indicating that the organic polymeriza-tion via methacryloxi groups was not favored, probably becausethe formation of voluminous side chains, which generated sterichindrance. These results agree with earlier works, where the pro-portions of Tn and Qn species were deduced from 29Si MAS-NMRspectra.

The 6′ signal seemed to have different behavior than 7′ and 8′

signals with composition. The presence of a higher amount of TMOS(R = 1 and 2) decreases the intensity of area of these three peaks(signals 6′, 7′ and 8′), being more visible for a ratio of 2. The vinylpolymerization was not favored and the organic condensation tookplace through SiOR groups (important decrease of the signal 4 andincrement of signals 6, 7 and 8, associated to CH2 = C groups andcarbonyl groups respectively). These results support those deducedfrom 29Si MAS-NMR spectra.

Therefore, based on these latter findings, it can be concludedthat the organic polymerization occurs via opening the C C dou-ble bond in films prepared with [TEOS]/[MPTS] and [TMOS]/[MPTS]mixtures. This is also confirmed by IR spectroscopy, where a strong

decrease of the intensity of 1630 cm−1 band associated with C Cbonds and the formation of a new band at 1730 cm−1, assigned tothe stretching vibration of C O not conjugated with C C bonds.

and [TMOS]/[MPTS].

Signals

4(51

ppm)

6`(58

ppm)

5(67

ppm)

6(126ppm)

7(136ppm)

8(168ppm)

8’(177ppm)

3.1 4.1 11.3 3.3 3.0 2.6 11.72.9 5.6 10.5 4.1 3.2 4.0 8.31.9 4.9 10.9 4.2 3.0 3.6 10.11.9 5.4 13.0 3.6 2.6 3.3 8.93.1 4.1 11.3 3.3 3.0 2.6 11.74.9 4.7 11.2 4.6 4.1 3.4 9.24.5 4.2 11.2 5.0 5.0 4.9 7.40.8 1.7 10.9 9.4 9.7 11.1 3.9

en produced through methacryloxy groups.

890 M. Criado et al. / Progress in Organic

210.502,1

2,2

2,3

2,4

2,5

2,6

2,7

2,8

2,9

3,0

3,1

"dto

tal"

valu

es

Molar ratios

[TEOS]/ [MPTS][TMOS]/ [MPTS ][TEOS]/ [MTES ][TMOS]/ [MTES]

Fs

wapidtiaaNFp[t[(rfip

tmpaidld

tacsp

4

s1os

[[[

[[[

[

[

[

[[

ig. 8. Evolution of the total dimensionality (dtotal) parameter of all hybrid materialsynthetized with the different molar ratios employed.

Finally, the dimensionality of the hybrid materials synthetizedas studied through “d” parameter, which provides information

bout the final structure achieved in films (see Table 1). The “d”arameter values are between 0 and 4, when d = 0 the structure

s formed by isolated tetrahedra; when d = 1, it is constituted byimeric units; when d = 2, linear chains are formed; when d = 3 or 4,he structure is bidimensional or tridimensional, respectively. Thenorganic dimensionality (d(T)), the organic dimensionality (d(Q))nd the total dimensionality (dtotal) parameters of hybrid materialsre depicted in Table 1. These parameters were obtained from 29SiMR-MAS spectra of the four hybrid organic–inorganic systems. Inig. 8 dtotal parameters of all studied mixtures are depicted. In sam-les with R = 0, hybrids with linear chains are formed in [TEOS] orTMOS]/[MPTS] mixtures (dtotal = 2.19) and more condensed struc-ures, between linear and planar structures, were developed inTEOS] or [TMOS]/[MTES] mixtures (dtotal = 2.66). The first reagentMPTS or MTES) provides the base structure of hybrids; the secondeagent (TEOS or TMOS) reacts with free Si O R bonds of T units,lling the holes and giving a final structure with lower porosity androbably greater thickness.

An increase of the amount of TEOS or TMOS in all studied mix-ures involved a higher dtotal value (see Fig. 8), indicating that a

ore complex and polymerized structure was formed. For exam-le, when a ratio R = 2 was used, dtotal values were between 2.76nd 2.99, that favors the formation of planar structures. In general,t is observed that hybrids synthetized from MTES present a highertotal parameter than those synthetized from MPTS. This tendency isogical taking account that mixtures with MTES presented a higheregree of condensation (see Table 1).

The organic–inorganic coatings prepared with the mix-ures [TEOS]/[MTES] and [TMOS]/[MTES] mixtures can be goodlternatives for metal protection against corrosion in reinforcedoncrete structures (ratio of 1), because higher degree of conden-ation and dimensionality, display a bigger thickness and lowerorosity.

. Conclusions

TG thermograms of prepared [TEOS] or [TMOS]/[MPTS] hybrid

howed three types of weight losses. The first one visible below60 ◦C was due to the evaporation of ethanol and water. The sec-nd one produced between 160 ◦C and 470 ◦C, was attributed tocissions within polymer chains or to volatile compounds produced

[[

[

Coatings 77 (2014) 880–891

during condensation reactions between Si OH and Si OR (R: CH3and C2H5) in [TEOS] or [TMOS]/[MTES] mixtures. The third loss wasassociated to the dehydration of silanol groups, or to the oxidationor degradation of MTES methyl groups.

FTIR spectra showed that the formation of hybrids materialsfrom [TEOS]/[MPTS] and [TMOS]/[MPTS] mixtures was producedthrough the reaction of Si OR groups, the condensation of silanols(inorganic condensation) and the formation of an interconnectedorganic polymer via C C opening of MPTS. FTIR spectra showedthat the formation of the hybrids prepared from [TEOS]/[MTES]and [TMOS]/[MTES] mixtures was mainly produced through thereaction of Si OR groups.

29Si MAS NMR spectra showed that a higher amount of TEOS orTMOS in the mixture with MPTS favored the inorganic condensa-tion; however, the organic polymerization (through methacryloxygroups), the mobility of the organic groups and the degree oforganic polymerization were less favored. The total condensationdegrees in [TEOS] or [TMOS]/[MTES] hybrids were higher thanthose obtained in [TEOS] or [TMOS]/[MPTS], so MTES favors theformation of branched organic structures.

Acknowledgment

M. Criado expresses her gratitude to the Spanish Ministry ofScience and Innovation for the Juan de la Cierva (Ref. JDC-2010)contract.

Appendix A. Supplementary data

Supplementary data associated with this article can be found,in the online version, at http://dx.doi.org/10.1016/j.porgcoat.2014.01.019.

References

[1] C. Sanchez, F. Ribot, New J. Chem. 18 (1994) 1007–1047.[2] C. Sanchez, B. Julián, P. Belleville, M. Popall, J. Mater. Chem. 15 (2005)

3559–3592.[3] R. Nass, E. Arpac, W. Glaubitt, H. Schmidt, J. Non-Cryst. Solids 121 (1990)

370–374.[4] A. Bordoli, N.T. Mathew, F. Lefebure, S.B. Halligudi, Microporous Mesoporous

Mater. 115 (2008) 345–355.[5] D. Wang, G.P. Bierwagen, Prog. Org. Coat. 64 (2009) 327–338.[6] V.H.V. Sarmento, M.G. Schiavetto, P. Hammer, A.V. Benedetti, C.S. Fugivara,

P.H. Suegama, S.H. Pulcinelli, C.V. Santilli, Surf. Coat. Technol. 204 (2010)2689–2701.

[7] M.L. Zheludkevich, R. Serra, M.F. Montemor, I.M. Miranda Salvado, M.G.S. Fer-reira, Surf. Coat. Technol. 200 (2006) 3084–3094.

[8] T.L. Metroke, R.L. Parkhill, E.T. Knobbe, Prog. Org. Coat. 41 (2001)233–238.

[9] M.L. Zheludkevich, I.M. Miranda Salvado, M.G.S. Ferreira, J. Mater. Chem. 15(2005) 5099–5111.

10] S.K. Medda, D. Kundu, G. De, J. Non-Cryst. Solids 318 (2003) 149–156.11] G. Kickelbick, Prog. Polym. Sci. 28 (2003) 83–114.12] S.A. Pellice, R.J.J. Williams, I. Sobrados, J. Sanz, Y. Castro, M. Aparicio, A. Durán,

J. Mater. Chem. 16 (2006) 3318–3325.13] Y. Wei, D. Yang, L. Tang, J. Mater. Res. 8 (1993) 1143–1152.14] Y. Abe, Y. Honda, T. Gunji, Adv. Organomet. Chem. 12 (1998) 749–753.15] J. Méndez-Vivar, A. Mendoza-Bandala., J. Non-Cryst. Solids 261 (2000)

127–136.16] D. Massiot, F. Fayon, M. Capron, I. King, S. Le Calvé, B. Alonso, J.-O. Durand, B.

Bujoli, Z. Gan, G. Hoatson, Magn. Reson. Chem. 40 (2002) 70–76.17] L. Jianguo, G. Gaoping, Y. Chuanwei, Surf. Coat. Technol. 200 (2006)

4967–4975.18] T.C. Chang, Y.T. Wang, Y.S. Hong, Y.S. Chiu, J. Polym. Sci. A: Pol. Chem. 38 (2000)

1972–1980.19] X. Chen, S. Zhou, B. You, L. Wu, Prog. Org. Coat. 74 (2012) 540–548.20] D.Y. Nadargi, A. Venkateswara Rao, J. Alloys Compd. 467 (2009)

397–404.

21] G. Li, M. Kanezashi, T. Tsuru, J. Membr. Sci. 379 (2011) 287–295.22] E.E. Pretsch, P. Bühlmann, C. Affolter, A. Herrera, R. Martínez, Determinación

estructural de compuestos orgánicos, Barcelona, Springer, 2001.23] R.M. Silverstein, F.X. Webster, Spectrometric Identification of Organic Com-

pounds, sixth ed., John Wiley and Sons, New York, 1998.

rganic

[

[[

[

[Chem. Mater. 15 (2003) 1797–4790.

M. Criado et al. / Progress in O

24] J. Habsuda, G.P. Simon, Y.B. Cheng, D.G. Hewitt, D.A. Lewis, H. Toh, Polymer 43(2002) 4123–4136.

25] J.R. Martínez, F. Ruiz, Rev. Mex Fís 48 (2002) 142–149.26] M. Lavorgna, L. Mascia, G. Mensitieri, M. Gilbert, G. Scherillo, B. Palomba, J.

Membr. Sci. 294 (2007) 159–168.27] M.C. Matos, L.M. Ilharco, R.M. Almeida, J. Non-Cryst. Solids 147–148 (1992)

232–237.

[

[

Coatings 77 (2014) 880–891 891

28] P. Innocenzi, G. Brusatin, S. Licoccia, M.L. Di Vona, F. Babonneau, B. Alonso,

29] S.-R. Zhai, Y. Song, B. Zhai, Q.-D. An, C.-S. Ha, Microporous Mesoporous Mater.163 (2012) 178–185.

30] Y.-H. Han, A. Taylor, M.D. Mantle, K.M. Knowles, J. Sol-Gel Sci. Technol. 43 (2007)111–123.