Complications in the 355 nm pulsed-laser polymerization of N-vinylcarbazole

The propagation kinetics of N-vinylcarbazole (NVC) were carefully investiga ted via the IUPAC-recommended pulsed-laser polymerization/size-exclusion ch romatography technique (PLP-SEC) in the temperature range between -20 and 2 0 degreesC using 355 nm pulsed irradiation and the photo initiator 2.2-dime thoxy-2-phenylacetophenone (DMPA) as a source of primary radicals. Using th is experimental approach, propagation rate coefficients, kp, were not acces sible for temperatures exceeding 20 degreesC. There is strong evidence that the monomer itself is excited by pulsed-laser light of 355 nm, thus contri buting to the polymerization process via the formation of free radicals. In addition, UV light-induced cationic polymerization processes can not be ig nored as a possible side reaction. NVC polymer also absorbs strongly at 355 nm and we speculate that this may lead to bond scission and branch network formation in the PLP process. Laser-controlled molecular weight distributi ons are only obtained for reaction temperatures below 20 degreesC. The appa rent Arrhenius parameters, E-A and A, are 22.8 kJ . mol(-1) and 3.6 x 10(7) L . mol(-1) . s(-1), respectively. These results are divergent from recent literature data.