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 Mw/Mn = 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.
Highlights
Poly(glycidyl methacrylate) (PGMA) and its copolymers have various industrial applications, such as coatings, adhesives, printing-ink, photo imaging [1], enzyme immobilization [2], and carbon dioxide fixation [3] based on the highly reactive pendant oxirane rings that provide the sequential ring-opening reactions
While the photosensitive onium salts play the role of the photo-acid generator of the initiator for the cationic ring-opening photopolymerization of the oxirane monomers, it has been reported that these onium salts serve as an accelerator for the controlled/living photoradical polymerization of methacrylate monomers using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) as the mediator [10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]
It was found that GMA selectively underwent controlled/living photoradical polymerization at the vinyl group using the MTEMPO mediator in the presence of the photosensitive onium salt, rather than the cationic ring-opening photopolymerization of the oxirane ring
Summary
Poly(glycidyl methacrylate) (PGMA) and its copolymers have various industrial applications, such as coatings, adhesives, printing-ink, photo imaging [1], enzyme immobilization [2], and carbon dioxide fixation [3] based on the highly reactive pendant oxirane rings that provide the sequential ring-opening reactions. While the photosensitive onium salts play the role of the photo-acid generator of the initiator for the cationic ring-opening photopolymerization of the oxirane monomers, it has been reported that these onium salts serve as an accelerator for the controlled/living photoradical polymerization of methacrylate monomers using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) as the mediator [10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]. It was found that GMA selectively underwent controlled/living photoradical polymerization at the vinyl group using the MTEMPO mediator in the presence of the photosensitive onium salt, rather than the cationic ring-opening photopolymerization of the oxirane ring. This paper describes the controlled/living photoradical polymerization of GMA using MTEMPO as the mediator in the presence of the photosensitive (4-tert-butylphenyl)diphenylsulfonium triflate (tBuS)
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