Kinetic Monte Carlo modeling to unravel the kinetics of light-driven step growth polymerization combined with RAFT polymerization

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1 Kinetic Monte Carlo modeling to unravel the kinetics of light-driven step growth polymerization combined with RAFT polymerization Lies De Keer, 1 Thomas Gegenhuber, 3 Paul H.M. Van Steenberge, 1 Anja S. Goldmann, 3 Marie-Françoise Reyniers, 1 Christopher Barner-Kowollik, 2,3 Dagmar R. D hooge 1 1 Laboratory for Chemical Technology (LCT), Ghent University Laboratory for Chemical Technology, Ghent University 2 School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology (QUT) 3 Preparative Macromolecular Chemistry, Karlsruhe Institute of Technology (KIT) BPG Annual meeting, Houffalize, Belgium, 04-05/05/2017

Zeppelin 1975) Light-induced reactions +

2 Light-driven polymerization And if You feel that You can t go on, in the Light You will find the Road. ( In the Light, Physical Graffiti, Led Zeppelin 1975) Light-induced reactions + overcome large barriers in short periods of time + environmental friendly conditions + spatial and temporal control Photoenol chemistry hν R = H, Ph photoenol 2

3 Polymer conjugation Functional groups within polymer backbone Conjugation of macromolecular building blocks Collective properties >>> sum of individual constituents Possible applications: 1. Hybrid systems synthetic + biological building blocks 2. Degradability introduced over complete length polymer chains 3

4 Polymerization concept and motivation A unique combination of light-driven step-growth and RAFT polymerization with styrene (M) bifunctional ortho-methyl benzaldehyde (AA) bisfumarate bearing a trithiocarbonate group (BB) 4

5 Outline Light-driven step-growth polymerization Monomer stability Kinetic Monte Carlo modeling strategy Experimental validation Mechanistic insights Chain extension via RAFT polymerization Kinetic Monte Carlo modeling strategy Experimental validation Mechanistic insights Conclusions 5

6 Monomer stability Benzaldehyde monomer (M2) is not stable k side benzaldehyde photoenol 6

7 Impact on step-growth polymerization Carothers equation step-growth polymerization r = N A,0 N B,0 X n = 1 r r 1 p r r = N A,0 N B,0 = 1.75 r = N A,0 N B,0 = 1 Experimental observation: stoichiometric imbalance for high chain length 7

8 Kinetic Monte Carlo modeling strategy Van Steenberge et al., Macromolecules 2012, 45,

9 k main /k side via dedicated experiments Monomer stability test k side Small molecule test k main r=1 r=1.43 monofunctional 9

10 Transition to step-growth polymerization r = N A,0 N B,0 r=1 [M1] 0 =[M2] 0 =0.02 mol L -1 r=1.75 [M1] 0 =0.04 mol L -1 [M2] 0 =0.07 mol L -1 Good agreement between experimental and simulated data 10

11 Mechanistic insights Excess of M2 Higher average chain length Longer M2M2 homopolymer chains if excess of M2 M2 Incorporation of M2M2 homopolymer after depletion of M1 M1 Copolymer Homopolymer Atypical step-growth behavior 11

12 Outline Light-driven step-growth polymerization Monomer stability Kinetic Monte Carlo modeling strategy Experimental validation Mechanistic insights Chain extension via RAFT polymerization Kinetic Monte Carlo modeling strategy Experimental validation Mechanistic insights Conclusions Styrene 12

13 Kinetic Monte Carlo modeling approach 12 dormant chain types 7 radical types > 200 reactions Novelty: Bivariate strategy: (1) chain length (2) amount of RAFT moieties for a given chain length Detailed characterization of polymer microstructure 13

14 Conventional RAFT polymerization Experimental validation Styrene Step-growth polymer precursor for r=1 [Styrene] 0 =8.74 mol L -1 [AIBN] 0 = mol L -1 Good agreement between experimental and simulated data 14

15 Step-growth precursor X styrene = 1 % Mechanistic insights Incorporation of styrene X styrene = 4 % X styrene = 7 % Chain extension ~ # RAFT Limited broadening 15

16 Outline Light-driven step-growth polymerization Monomer stability Kinetic Monte Carlo modeling strategy Experimental validation Mechanistic insights Chain extension via RAFT polymerization Kinetic Monte Carlo modeling strategy Experimental validation Mechanistic insights Conclusions 16

17 Conclusions Light-driven step-growth polymerization Identification of side reaction Use of excess allows to obtain high chain length Strong deviation from conventional Carothers behavior Chain extension via RAFT polymerization Full product evaluation of multifunctional RAFT agents Controlled incorporation of styrene Further optimization of conditions 17

Acknowledgments Fund for Scientific Research

Methusalem Funding by the Flemish Government

Institute of Technology, KIT, Germany Science

18 Acknowledgments Fund for Scientific Research Flanders (FWO; 1S37517N) Long Term Structural Methusalem Funding by the Flemish Government Interuniversity Attraction Poles Program Belgian State Belgian Science Policy (BELSPO) Macromolecular chemistry group, Karlsruhe Institute of Technology, KIT, Germany Science and Engineering Faculty, Queensland University of Technology, QUT, Australia 18

STEP-GROWTH POLYMERS AS MACRO CHAIN TRANSFER AGENTS AN EXPERIMENTAL AND THEORETICAL STUDY

T. Gegenhuber, L. De Keer, A. S. Goldmann, P.H.M. Van Steenberge, M.F. Reyniers, D. R. D hooge, C. Barner-Kowollik STEP-GROWTH POLYMERS AS MACRO CHAIN TRANSFER AGENTS AN EXPERIMENTAL AND THEORETICAL STUDY