Photo-living radical polymerization of methyl methacrylate using alkoxyamine as an initiator

The photo-radical polymerization of methyl methacrylate (MMA) was performed using 1-(cyano-1-methylethoxy)-4-methoxy-2,2,6,6-tetramethylpiperidine (CMTMP), an alkoxyamine, as the initiator. The polymerization only slightly occurred by CMTMP itself, however, it proceeded in the presence of bis(alkylphenyl)iodonium hexafluorophosphate (BAI), a photo-acid generator. The polymerization was confirmed to proceed in a living mechanism way based on the linear correlations for the three different plots of the first-order time-conversion, the reciprocal of the initial concentration of the CMTMP-molecular weight of the resulting polymer, and the conversion-molecular weight. It was suggested that the electron transfer occurred between BAI and MTEMPO in the excited state during the propagation, while the phenyl radical generated from an excess of BAI also initiated the polymerization to produce a polymer with a lower molecular weight during the very early stage. The participation of the excited BAI in the propagation was also demonstrated by the photo-latency of the polymerization.