Controlled radical photopolymerization of n-butyl methacrylate(n-BMA) mediated by 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy(HTEMPO) was carried out in bulk at ambient temperature. It was found that obtained n-BMA homopolymers exhibited narrow polydispersities of around 1.4, which was characterized by GPC. Plots of number-average molecular weight vs. conversion and Ln([M0]/[M]) vs. time were liner respectively, indicating that was a controlled photopolymerization.
The photoinduced bulk polymerization of a reactive-hindered amine light stabilizers(r-HALS), 4-acryloyl-2, 2, 6, 6-tetramethylpiperidinyl (ATMP), was performed at 80 ℃ by using aDPC technique. An unique periodic exponential attenuation-type oscillating curve was foundwhen the polymerization was carried out in air, but this phenomenon was not found in nitrogen.It is supposed that this unique kinetic performance may be attributed to nitroxyl radicals that areproduced in situ from the oxidation of ATMP. ATMP polymer with narrow polydispersity (d =1.03) can be obtained by photoinduced solution polymerization of ATMP. The signal detected inESR may be assigned to the nitroxyl radicals in the matrix of ATMP polymer. Since this kind ofrecycling of nitroxyl radicals is well documented for the photostabilizing mechanism of HALS, thepresent results may serve as a kinetic evidence for this mechanism.
