Abstract:

Controlled/living photopolymerization of methyl methacrylate(MMA) mediated by bimolecular systems for 4-hydroxy-2,2,6,6-tetramethyl-piperidinyl-1-oxyl(HTEMPO) and 2,2,6,6-tetramethyl-piperidinone(TMPD) was performed at ambient temperature. The effects of HTEMPO, TMPD and their different molar ratio as a mediator and photo-induced oxidization in situ of TMPD in the system were discussed respectively. It is shown that the molecular weight(Mn) of MMA homopolymer increased linearly and the polydispersity index(PDI) decreases with the conversion increasing, even until the conversion up to 80%, mediated by bimolecular system with both HTEMPO and TMPD, which is the characteristic of a controlled/living free radical polymerization. It is found that the obtained MMA homopolymer prepared by the photopolymerization exhibited a narrow molecular weight distribution as was characterized by GPC, the smallest value of PDI is 1.2. The result also shows that the bimolecular systems with HTEMPO/TMPD as a mediator has a  better controlling kinetic performance than that only mediated by HTEMPO under the same condition.

Key words: Controlled/living photopolymerization; Methyl methacrylate; Nitroxide; HTEMPO;