Synthesis of block copolymers by combination of ATRP and photoiniferter processes

Background: Block copolymers of monomers polymerizing by different mechanisms can be prepared by the transformation approach. A wide range of combinations of different polymerization modes has been reported in the literature. In this work, the transformation approach was further extended to the preparation of block copolymers by combining atom transfer radical polymerization (ATRP) and photoiniferter processes. Results: Photoactive morpholine-4-dithiocarbamate-terminated polystyrene (MDC-PS-MDC) was prepared by the reaction of dibrominated polystyrene, obtained by ATRP, with morpholine-4-dithiocarbamate sodium salt in dimethylformamide. The structure of MDC-PS-MDC was confirmed by ¹H NMR and UV-visible spectral analysis. The ability of MDC-PS-MDC to act as a photoiniferter for the block copolymerization of methyl acrylate was examined. The polymerization shows a 'living' character at up to 25% conversion and produces well-defined polymers with molecular weights close to those predicted from theory and relatively narrow polydispersities (M_w/M_n ≈ 1.40). Conclusion: It is demonstrated that the end groups of polymers obtained by ATRP can be converted into morpholino-4-dithiocarbamate groups which act as photoiniferters. In this way, the desired mechanistic transformation between two controlled free radical polymerization methods can be achieved.