Nitroxide-mediated photo-living radical polymerization of methyl methacrylate using (4-tert-butylphenyl)diphenylsulfonium triflate as a photo-acid generator

The photo-living radical polymerization of methyl methacrylate (MMA) was performed at room temperature using (2RS, 2'RS)-azobis(4-methoxy-2,4-dimethylvaleronitrile) (r-AMDV) as the initiator, 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) as the mediator, and (4-tert-butylphenyl)diphenylsulfonium triflate ((t)BuS) as the photo-acid generator. The livingness of the polymerization was confirmed on the basis of linear increases in the ln ([MMA](0)/[MMA](t)) vs. time and in the molecular weight vs. the conversion. The molecular weight distributions of the resulting polymers were around 1.45. The polymerization rate was dependent both on the (t)BuS/MTEMPO and MTEMPO/r-AMDV molar ratios. Furthermore, it was found that the polymerization had a photo-latency because the polymerization was retarded by the interruption of the irradiation; however, it was accelerated again by further irradiation without deactivation of the growing polymer chain ends.