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

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1 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 a university for the CRICOS No J real world

2 The Road into the Light? 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) Tetrazole to Nitrile-imine Methyl- Benzaldehyde to Photoenol Phenacylsulfide to Thioaldehyde Azirine to Nitrile-ylide 2 13 th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

3 Reaction Pathway and Motivation Incorporation of RAFT group within the backbone of a stepgrowth polymer 3 13 th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

4 General Polymerization Concept Step-growth polymerization using a bifunctional ortho-methyl benzaldehyde and a bisfumarate with a trithiocarbonate group M1 P1 Chain extension by conventional RAFT polymerization P th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

5 Monomer Stability and Homopolymerization Irradiation with conditions for step-growth polymerization of M1 and Determination of k side PS calibration Intensity/ a.u. M1 Simulation Normalized RI Response M1 M1 after irradiation after irradiation log(m) log(m) RAFT-fumarate M1 stable, benzaldehyde reacts with itself 5 13 th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

6 Side Reactions and k side Determination Possible side reactions of activated ortho-quinodimethane and the carbonyl species of the benzaldehyde Determination of k main in relation to k side via small molecules F F--F 6 13 th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

7 k main vs. k side and Off-Stoichiometry in Simulations Side reaction, imbalance and k values c X / mol L AA AF r = 1 k side = k main Time / min r = N A,0 N F,0 f AB k side / k main r = k side < k main k side = k main f AB k side > k main If k side = k main, still strong suppression of side reaction With excess A more side reaction occuring r 7 13 th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

8 Small Molecule Reaction: k main Determination F r = 1 r = F--F r = 1 r = 1.43 Normalized RI Response normalized f m F log(m) log(m) Conversion (NMR): 93 % Conversion (NMR): 87 % r = 1 with k side = 0.2 k main 8 13 th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

9 Step-Growth Polymerization Kinetics with Equimolarity Normalized RI Response r = 1 and k side = 0.2 k main t 0 10 min 20 min 30 min 45 min 1 h 4 h 8 h X w Experimental Simulation Retention time / min Conversion / % 9 13 th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

10 Step-Growth with Imbalance using the Side Reaction Increasing the amount of (photoenol) Highest M w for the 1/1.75 ratio of M1/ (excess photoenol) At ½ ratio decrease of the M w M1 r = N N M1 Normalized RI Response r = 0.99 r = 1.05 r = 1.20 r = 1.30 r = 1.50 r = 1.75 r = 2.00 M w / kg mol M w (exp.) 70 trendline Retention time / min r th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

11 Step-Growth Polymerization with Off-Stoichiometry Excess of (also increased concentration, c(m1) = const.) High molecular weight species formed due to coupling of further Experimental Simulation Normalized RI Response M1 M1 t 0 10 min 20 min 30 min 45 min 60 min 90 min 2 h 4 h 6 h Retention time / min X w mass fraction homopolymer Conversion / % r = 1 r = Conversion / % th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

12 Mechanistic Considerations Insertion of homopolymer in M1M1 (+M1) copolymer after exhaustion of Formation of high molecular species according to Carother M1 Homopolymer Copolymer th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

13 Chain Extension by RAFT Polymerization Conventional RAFT polymerization using step-growth polymer with ratio of 1/1.5 M1/ (1/1.75 polymer with solubility issues) Normalized Intensity Step-growth 0.25 h 0.5 h 1 h 1.5 h 2 h 3 h 4 h M n / kg mol log(m) Conversion / % th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

14 Mechanistic Considerations Symmetric trithiocarbonate fragmentation in a random fashion Up to 200 different reactions theoretical taken in account Statistical balancing of chain length by mixing long and short chains during the addition and fragmentation th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

15 Summary Step-growth polymerization by light-induced reactions Use of ortho-quinodimethanes and fumarates Side reaction and theoretical description of k side /k main Off-stoichiometry to obtain high molecular species Chain extension by RAFT polymerization Controlled reactio Calculations and simulations currently under investigation High molecular species obtained th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch

16 Acknowledgements Barner-Kowollik Team Prof. Dagmar D hooge and colleagues Follow th April 2017 UNESCO IUPAC Conference on Macromolecules & Materials 2017, Stellenbosch