KINETIC MODELING OF ATOM TRANSFER RADICAL … Carolina... · A kinetic model has been developed for the ATRP of n-butyl acrylate allowing the simulation of the conversion, the number

KINETIC MODELING OF ATOM TRANSFER RADICAL POLYMERIZATION

OF n-BUTYL ACRYLATE

Methusalem Advisory Board Meeting, Gent, June 28, 2010

Laboratory for Chemical Technology, Ghent Universityhttp://www.lct.UGent.be

OF n-BUTYL ACRYLATE

Carolina Toloza Supervisors: Marie-Françoise Reyniers and Guy B. Marin

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Radical polymerizations: techniques (1)1. Free Radical Polymerization (FRP)

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Radical polymerizations: techniques (2)2. Controlled Radical Polymerization (CRP)

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Limit: no termination and transfer: living polymerization

Controlled radical polymerization: goals

homopolymer

block copolymer

Composition:Functionality: Topology:

end-functional polymers

side-functional polymers

XX

X

XXX

linearnetwork/

crosslinked

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graft copolymermultifunctional polymers

XXX

XXX

X

XXX

XX

YX

X

stardendritic/

hyperbranched

Chain length:

start half-way end

Outline

• Modeling radical polymerizations• Principle of ATRP• Reaction scheme of ATRP of n-butyl acrylate• Molecular diffusion• Importance of backbiting and deactivation


• Importance of backbiting and deactivation• Conclusions and future work

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Modeling radical polymerizationsMethusalem Advisory Board Meeting, Gent, June 28, 2010

moleculardiffusion

reactor configuration

reactor model

monomer(s)initiator, …

polymerizationconditions

intrinsic kinetics& thermo

reactionnetwork

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rate equations

moment equations

averages of MMD

polymer structure

conversion full MMD

kinetic lab scaletests

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Principle of ATRPMethusalem Advisory Board Meeting, Gent, June 28, 2010

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ATRP system

Cu(II)Br2

Transition metal saltCopper(II)Bromide

Monomern-butyl acrylate

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Cu(I)Br

LigandN,N,N’,N′′,N′′-Pentamethyl-

diethylenetriamine(PMDETA)

InitiatorMethyl-2-

Bromopropionate(MBP)

Transition metal saltCopper(I)Bromide


Reaction Scheme

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End and mid-chain radical

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kchemk+diff

k-diff

apparent reactivitykapp

A + B A B C A + B C

Molecular diffusion (1)

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ABAdiff DNk σπ4=+

Smoluchowski model:

k+diff : f(conversion, diffusion model(chain length))

σ: reaction distance; DAB: mutual diffusion coefficient

kchem : Arrhenius equation

−=

RT

EAk ABa

ABchem,exp

AB A BD D D= + Free volume theory


Molecular diffusion (2)

ATRP of n-BuAat 353K in bulk

Apparent reactivity important on deactivation at high monomer conversion

12wm: mass fraction of monomer i,j: chain length

Apparent reactivity most pronounced on termination

at higher chain length

wm=0.3

Molecular diffusion (3)Methusalem Advisory Board Meeting, Gent, June 28, 2010

Too low simulated

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rate of polymerization

Due to diffusional limitations on deactivation

Too low simulated level of branching

Kinetic parameters (model with diffusion)Methusalem Advisory Board Meeting, Gent, June 28, 2010

Reaction step (l)kl,chem

(L mol -1 s-1) or (s -1) Literature Model

Propagation (end) kpend 4.96E+04a 4.13E+04

Transfer to monomer ktrM 4.35a 4.35

Backbiting kbb 3.81E+02a 2.54E+02

Propagation (mid) kpmid 4.96E+02a 2.76E+02

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Activation (end) kaend 1.48b 7.39E-01

Deactivation (end) kdaend - 2.96E+09

Activation (mid) kamid 5.78b 5.78

Deactivation (mid) kdamid - 1.16E+10

Termination by recombination ktc 2.00E+08a 2.00E+09

ATRP equilibrium coefficient Keq - 5.00E-10

Very good agreement with available literature data of kinetic parameters

aWang et al. Macromol. Rapid Commun. 30, 2022 2009bSeeliger and Matyjaszewski Macromolecules 42, 6050 2009


Importance of backbiting

kbb = 3810 s-1

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Significant effect on conversion and branching levels

kbb = 254 s-1

kbb = 0 s-1


Importance of backbiting and deactivation

kbb = 381 s-1

kdaend=

7.39 e+8 L mol -1 s-1

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Backbiting decreases the ATRP rate and increases the branching level

The end- and mid-chain radical concentration and ATRP rate are significantly influenced by deactivation

kbb = 254 s-1

kbb = 0 s-1

kdaend =

2.96 e+9 L mol -1 s-1

Conclusions and future workMethusalem Advisory Board Meeting, Gent, June 28, 2010

1. A kinetic model has been developed for the ATRP of n-butyl acrylate allowing thesimulation of the conversion, the number average molar mass, the polydispersityindex, the polymer end group functionality and the branching level as a functionof polymerization time and conditions. A good description of experimentalpolymerization data from literature is obtained using kinetic parameters reportedin literature.

2. Diffusional limitations are found to be important both for termination anddeactivation and influencing the polymerization rate and the level of branching

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deactivation and influencing the polymerization rate and the level of branchingsignificantly.

3. The effect of backbiting on the number average chain length and thepolydispersity index is limited.

4. The importance of βC-scission and intermolecular chain transfer to polymerreactions on the ATRP will be evaluated in the near future.

5. Kinetic parameters based on experimental data will be determined in the nearfuture.

Acknowledgments Methusalem Advisory Board Meeting, Gent, June 28, 2010

This work is supported by the Long Term Structural Methusalem Funding by the Flemish Government – grant number BOF09/01M00409

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Thank you


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KINETIC MODELING OF ATOM TRANSFER RADICAL … Carolina... · A kinetic model has been developed for the ATRP of n-butyl acrylate allowing the simulation of the conversion, the number