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