Selective controlled/living photoradical polymerization of glycidyl methacrylate, using a nitroxide mediator in the presence of a photosensitive triarylsulfonium salt

Abstract

The controlled/living photoradical polymerization of glycidyl methacrylate (GMA) was attained using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) as the mediator and (2RS,2'RS)-azobis(4-methoxy-2,4-dimethylvaleronitrile) as the initiator in the presence of (4-tert-butylphenyl)diphenylsulfonium triflate (tBuS). Whereas the polymerization in the absence of MTEMPO yielded a gel-containing polymer, the MTEMPO-mediated polymerization produced poly(GMA) bonded at the vinyl site, and retained the oxirane ring structure. No occurrence of the cationic ring-opening photopolymerization of the oxirane ring even in the presence of the photosensitive onium salt indicated that tBuS served as the photoelectron transfer agent between MTEMPO in their excited states at the propagating chain end. The resulting polymers had comparatively narrow molecular weight distributions of M w/M n = 1.46-1.48. The living nature of the MTEMPO-mediated polymerization was confirmed on the basis of a linear increase in the conversion-molecular weight plots and gel permeation chromatography (GPC) analysis. © 2012 by the authors.