Enhancing Control in the RAFT Copolymerization of N-Vinyl Formamide and N-Vinyl Pyrrolidone Through Low-Temperature Photoinitiation

초록

Copolymers of N-vinyl formamide (NVF) and N-vinyl pyrrolidone (NVP) with controlled molecular weight (MW) and narrow molecular weight distribution were successfully synthesized via xanthate-mediated Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization. The RAFT homopolymerization of NVF showed inefficient chain transfer to the chain transfer agent, which was attributed to the rapid propagation of NVF. Two strategies were employed to improve controllability: copolymerization with NVP and photoinitiated RAFT polymerization at lower temperatures. Although copolymerization with NVP improved control compared to NVF homopolymerization, dispersity increased during polymerization owing to the persistently fast propagation of NVF. In contrast, low-temperature photoinitiated RAFT polymerization effectively moderated the polymerization kinetics and enhanced chain transfer efficiency. Under optimized conditions (10 degrees C, low-intensity blue LED irradiation), well-defined copolymers were obtained with dispersity values as low as D similar to 1.16, while maintaining an NVF content exceeding 50% and predictable MW evolution. Subsequent hydrolysis yielded vinyl amine-containing copolymers, as confirmed by NMR spectroscopy. This approach provides a practical route to well-defined NVF- and vinyl amine-based copolymers.

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