31P-NMR CHARACTERIZATION OF CHAIN ENDS IN POLYMERS AND COPOLYMERS PREPARED USING LUCIRIN TPO AS A PHOTOINITIATOR

P-NMR spectra of polymers and copolymers prepared from styrene, substituted sty - renes, methyl methacrylate and methyl acrylate using diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (Lucirin TPO) as a photoinitiator are interpreted and analyzed. The spectra provide information about the structures and configurations of phosphorus-co ntaining end groups. The relative amounts of various chain ends present in TPO-initiated copolymers correspond well with the relative amounts of monomers employed in copolymerizations, indicating that photogenerated diphenylphosphine oxide radicals are nonselective in reactions toward the monomers investigated. This result is consistent with the high reactivity reported previously for diphenylphosphine oxide radicals but is not in agreement with the results of time-resolved ESR measurements, which indicate that the diphenylphosphinyl radical is more reactive toward methyl methacrylate than toward styrene by a factor of 1.45.