Effects of UV energy on photo-initiated RAFT process of N-vinyl pyrrolidone

Abstract

Poly (N-vinyl pyrrolidone) was successfully prepared via photo-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization. Methyl (ethoxycarbonothioyl)sulfanyl propionate, used as a chain transfer agent (CTA), undergoes UV-induced photolysis, making it ineffective for the polymerization reaction. To prevent the photolysis of CTA, a photo-initiated RAFT process was carried out using a light emitting diode with narrow-band emission at approximately 410 nm. Photolysis of CTA was effectively prevented, where plots of the ln ([M]0/[M]) vs. time and molecular weight vs. conversion data obtained during the polymerization reaction were linear. Furthermore, it was confirmed that the system was perfectly controlled by light through a light on/off switching test, and the syndiotacticity could be increased by polymerization with fluoroalcohol at low temperature.