KINETIC MODELING OF ATOM TRANSFER RADICAL POLYMERIZATION OF n -BUTYL - - PowerPoint PPT Presentation

KINETIC MODELING OF ATOM TRANSFER RADICAL POLYMERIZATION OF n-BUTYL ACRYLATE

Methusalem Advisory Board Meeting, Gent, June 28, 2010

Laboratory for Chemical Technology, Ghent University http://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

X X X X X X

linear network/ crosslinked

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graft copolymer multifunctional polymers

X X XX X X X X X X X X Y XX

star dendritic/ 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

Methusalem Advisory Board Meeting, Gent, June 28, 2010

• Importance of backbiting and deactivation
• Conclusions and future work

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Modeling radical polymerizations

Methusalem Advisory Board Meeting, Gent, June 28, 2010

molecular diffusion reactor configuration reactor model monomer(s) initiator, … polymerization conditions intrinsic kinetics & thermo reaction network

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rate equations moment equations averages of MMD polymer structure conversion full MMD kinetic lab scale tests

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Principle of ATRP

Methusalem Advisory Board Meeting, Gent, June 28, 2010

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Methusalem Advisory Board Meeting, Gent, June 28, 2010

ATRP system

Cu(II)Br2

Transition metal salt Copper(II)Bromide Monomer n-butyl acrylate

8 Cu(I)Br

Ligand N,N,N’,N′′,N′′- Pentamethyl- diethylenetriamine (PMDETA) Initiator Methyl-2- Bromopropionate (MBP) Transition metal salt Copper(I)Bromide

Methusalem Advisory Board Meeting, Gent, June 28, 2010

Reaction Scheme

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Methusalem Advisory Board Meeting, Gent, June 28, 2010

End and mid-chain radical

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Methusalem Advisory Board Meeting, Gent, June 28, 2010

kchem k+diff k-diff

apparent reactivity

kapp

A + B A B C A + B C

Molecular diffusion (1)

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AB A diff

D N k σ π 4 =

+

Smoluchowski model: k+diff : f(conversion, diffusion model(chain length)) σ: reaction distance; DAB: mutual diffusion coefficient kchem: Arrhenius equation

       − = RT E A k

AB a AB chem ,

exp

AB A B

D D D = +

Free volume theory

Methusalem Advisory Board Meeting, Gent, June 28, 2010

Molecular diffusion (2)

ATRP of n-BuA at 353K in bulk

Apparent reactivity important

• n deactivation at high

monomer conversion

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wm: 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) kp

end

4.96E+04a 4.13E+04 Transfer to monomer ktrM 4.35a 4.35 Backbiting kbb 3.81E+02a 2.54E+02 Propagation (mid) kp

mid

4.96E+02a 2.76E+02

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Activation (end) ka

end

1.48b 7.39E-01 Deactivation (end) kda

end

• 2.96E+09

Activation (mid) ka

mid

5.78b 5.78 Deactivation (mid) kda

mid

• 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 2009 bSeeliger and Matyjaszewski Macromolecules 42, 6050 2009

Methusalem Advisory Board Meeting, Gent, June 28, 2010

Importance of backbiting

kbb = 3810 s-1 15

Significant effect

• n conversion

and branching levels

kbb = 254 s-1 kbb = 0 s-1

Methusalem Advisory Board Meeting, Gent, June 28, 2010

Importance of backbiting and deactivation

kbb = 381 s-1

kda

end=

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

kda

end =

2.96 e+9 L mol-1 s-1

Conclusions and future work

Methusalem Advisory Board Meeting, Gent, June 28, 2010

• 1. A kinetic model has been developed for the ATRP of n-butyl acrylate allowing the

simulation of the conversion, the number average molar mass, the polydispersity index, the polymer end group functionality and the branching level as a function

• f polymerization time and conditions. A good description of experimental

polymerization data from literature is obtained using kinetic parameters reported in literature.

• 2. Diffusional limitations are found to be important both for termination and

deactivation and influencing the polymerization rate and the level of branching

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deactivation and influencing the polymerization rate and the level of branching significantly.

• 3. The

effect

• f

backbiting

• n

the number average chain length and the polydispersity index is limited.

• 4. The importance of βC-scission and intermolecular chain transfer to polymer

reactions on the ATRP will be evaluated in the near future.

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

future.

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

Methusalem Advisory Board Meeting, Gent, June 28, 2010

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