Investigation of nitroxide-mediated radical polymerization of methacrylates initiated by PS-TEMPO adduct

摘要

Nitroxide-mediated radical polymerization (NMRP) of methacrylate monomers is among the research interests of many polymer synthetic chemists. Hawker et al. reported the synthesis of well-defined random copolymers of methacrylate and styrene by nitroxide-mediated radical copolymerization with high styrene fractions in the feed, and the synthetic strategy was further applied to synthesize poly(styrene-b-(styrene-co-n-butyl methacrylate)) block copolymer by Butz et al. The kinetics of nitroxide-mediated radical copolymerization of butyl mathacrylate with styrene was investigated by Cuervo-Rodriguez et al. However, many attempts to homopolymerize methacrylates by NMRP yielded polymers with very low conversions. Such results generally were ascribed to the degradation of propagating radicals via β-hydrogen abstraction by nitroxide (Figure 1), followed by the formed hydroxylamine acting as a chain transfer agent to terminate another propagating chain with nitroxide recovered. Most recently, White et al. reported high conversion in radical polymerization of methacrylates by using new types of metal-free spin-traps other than TEMPO, but the polydispersities of polymers yielded were relatively high (1.6-2.17).