31P-NMR CHARACTERIZATION OF CHAIN ENDS IN POLYMERS AND COPOLYMERS PREPARED USING LUCIRIN TPO AS A PHOTOINITIATOR
Robert E. Medsker, Manuel Chumacero, Everett R. Santee, Anton Sebenik and H. James Harwood
Maurice Morton Institute and Department of Polymer Science The University of Akron, Akron, Ohio 44325-3909
31P-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 informa-tion about the structures and configurations of phosphorus-containing end groups. The relative amounts of various chain ends present in TPO-initiated copolymers correspond well with the rela-tive amounts of monomers employed in copolymerizations, indicating that photogenerated diphen-ylphosphine oxide radicals are nonselective in reactions toward the monomers investigated. This result is consistent with the high reactivity reported previously for diphenylphosphine oxide radi-cals 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 sty-rene by a factor of 1.45.