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M. Kury, K. Seidler, A. Svirkova, M. Marchetti-Deschmann, T. Koch, C. Gorsche, R. Liska:
"Addition-Fragmentation Chain Transfer Reagents in Photopolymerization of Acrylates";
Poster: 4th European Symposium of Photopolymer Science, Leipzig; 2016-09-11 - 2016-09-14; in: "ESPS 2016", (2016), P-57.

In photopolymerization glassy networks are formed by free radical polymerization of multifunctional monomers. Resulting materials tend to be rather brittle and exhibit an inhomogeneous network structure due to an uncontrolled radical curing mechanism.
Addition-fragmentation chain transfer (AFCT) reagents1 transform this uncontrolled chain-growth reaction to a mixed chain-growth/step-growth-like process, which yields materials with more regulated network architectures and tunable mechanical properties.
β-Allyl sulfones2,3 and vinyl sulfonates4,5 are promising classes of AFCT reagents. Applied to methacrylate-based polymer networks, higher conversion at the gel point leading to lower shrinkage stress, higher overall conversion and an increase in impact resistance have been reported.
Recently, mechanistic photoreactor and Maldi-TOF studies have shown a similar behavior of AFCT reagents towards monofunctional acrylates. Moreover, a study with diacrylates gave detailed information about the co-reactivity of AFCT reagents in acrylate-based formulations (RT-NIR photorheology). Various mechanical tests were carried out to proof the formation of more homogeneous networks (DMTA), leading to improved mechanical properties.