Methusalem Advisory Board Meeting, Gent, June 28, 2010 KINETIC MODELING OF ATOM TRANSFER RADICAL POLYMERIZATION OF n -BUTYL ACRYLATE OF n -BUTYL ACRYLATE Carolina Toloza Supervisors: Marie-Françoise Reyniers and Guy B. Marin Laboratory for Chemical Technology, Ghent University http://www.lct.UGent.be 1
Radical polymerizations: techniques (1) 1. Free Radical Polymerization (FRP) 2
Radical polymerizations: techniques (2) 2. Controlled Radical Polymerization (CRP) Limit: no termination and transfer: living polymerization 3
Controlled radical polymerization: goals Functionality: Composition: Topology: end-functional polymers homopolymer network/ side-functional polymers block copolymer linear crosslinked X X X X X X X X X X X XX X X X XX X Y X dendritic/ star multifunctional polymers graft copolymer hyperbranched Chain length: start half-way end 4
Methusalem Advisory Board Meeting, Gent, June 28, 2010 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 5
Methusalem Advisory Board Meeting, Gent, June 28, 2010 Modeling radical polymerizations polymerization monomer(s) conditions initiator, … reactor configuration reaction intrinsic kinetics molecular network & thermo diffusion reactor model kinetic lab scale rate equations tests moment equations averages of MMD polymer conversion full MMD structure 6 6
Methusalem Advisory Board Meeting, Gent, June 28, 2010 Principle of ATRP 7
Methusalem Advisory Board Meeting, Gent, June 28, 2010 ATRP system Monomer n- butyl acrylate Transition metal salt Copper(II)Bromide Cu(II)Br 2 Ligand Initiator N,N,N’,N ′′ ,N ′′ - Methyl-2- Cu(I)Br Pentamethyl- Bromopropionate diethylenetriamine (MBP) (PMDETA) Transition metal salt Copper(I)Bromide 8
Methusalem Advisory Board Meeting, Gent, June 28, 2010 Reaction Scheme 9
Methusalem Advisory Board Meeting, Gent, June 28, 2010 End and mid-chain radical 10
Methusalem Advisory Board Meeting, Gent, June 28, 2010 Molecular diffusion (1) apparent reactivity k +diff k chem k app A + B A B C A + B C k -diff k +diff : f(conversion, k chem : Arrhenius equation diffusion model(chain length)) − E Smoluchowski model: exp , a AB 4 = k A = π σ k N D chem AB RT + diff A AB σ : reaction distance; D AB : mutual diffusion coefficient = + D D D Free volume theory AB A B 11
Methusalem Advisory Board Meeting, Gent, June 28, 2010 Molecular diffusion (2) Apparent reactivity important ATRP of n- BuA on deactivation at high at 353K in bulk monomer conversion w m =0.3 Apparent reactivity most pronounced on termination at higher chain length 12 w m : mass fraction of monomer i,j: chain length
Methusalem Advisory Board Meeting, Gent, June 28, 2010 Molecular diffusion (3) Too low simulated rate of polymerization Too low simulated level of branching Due to diffusional limitations on deactivation 13
Methusalem Advisory Board Meeting, Gent, June 28, 2010 Kinetic parameters (model with diffusion) k l,chem Reaction step (l) Literature Model (L mol -1 s -1 ) or (s -1 ) k p end 4.96E+04 a Propagation (end) 4.13E+04 k trM 4.35 a Transfer to monomer 4.35 Backbiting k bb 3.81E+02 a 2.54E+02 k p mid Propagation (mid) 4.96E+02 a 2.76E+02 k a end Activation (end) 1.48 b 7.39E-01 k da end Deactivation (end) - 2.96E+09 k a mid Activation (mid) 5.78 b 5.78 k da mid Deactivation (mid) - 1.16E+10 k tc Termination by recombination 2.00E+08 a 2.00E+09 K eq ATRP equilibrium coefficient - 5.00E-10 Very good agreement with available literature data of kinetic parameters a Wang et al. Macromol. Rapid Commun. 30, 2022 2009 b Seeliger and Matyjaszewski Macromolecules 42, 6050 2009 14
Methusalem Advisory Board Meeting, Gent, June 28, 2010 Importance of backbiting k bb = 3810 s -1 k bb = 254 s -1 Significant effect on conversion and branching levels k bb = 0 s -1 15
Methusalem Advisory Board Meeting, Gent, June 28, 2010 Importance of backbiting and deactivation k da end = 7.39 e+8 L mol -1 s -1 k bb = 381 s -1 k da end = k bb = 254 s -1 2.96 e+9 L mol -1 s -1 The end- and mid- Backbiting chain radical k bb = 0 s -1 decreases the concentration and ATRP rate and ATRP rate are increases the significantly influenced branching level by deactivation 16
Methusalem Advisory Board Meeting, Gent, June 28, 2010 Conclusions and future work 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 of 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 deactivation and influencing the polymerization rate and the level of branching significantly. 3. The effect of backbiting on the number average chain length and the polydispersity index is limited. 4. The importance of β C-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. 17
Methusalem Advisory Board Meeting, Gent, June 28, 2010 Acknowledgments This work is supported by the Long Term Structural Methusalem Funding by the Flemish Government – grant number BOF09/01M00409 18
Methusalem Advisory Board Meeting, Gent, June 28, 2010 Thank you 19
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