Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Kinetics of Photoinduced Radical Polymerization with Electron Donor/Electron Acceptor Initiator SystemsBy means of benzyltriphenylphosphonium tetrafluoroborate (P⊕) and anthracene (An) as photoinitiator system and methylmethacrylate (MMA) as monomer the influences of several reaction parameters on the polymerization quantum yield Φp, were studied. The following principal reactions proceed: electron transfer between excited An (1An) and P⊕ salt (kq = 2,5 · 109 M-1 s-1), quenching of 1An by MMA (kqMMA = 1,3 · 107 M-1 s-1), reaction between a 1An…P⊕ salt complex and MMA. The last reaction is assumed, since from the disappearance of An and the formation of An cation radical, respectively, rate constants kqMMA 〉 108 M-1 s-1 have been calculated. Furthermore, it is assumed, that only the quenching of 1An by MMA (Φp = 3,8) and the addition of free radicals, produced by the photoinduced electron transfer, lead to polymer formation. Kinetic equations were developed, which can explain the effect of P⊕-salt concentration, light intensity and MMA concentration on Φp data. The quotient obtained for kp/kt0,5 is in the range of 0,053 to 0,087 M-0,5 s-0,5, depending on the used experimental parameters. Polymerization degrees Pn of 260-590 were found, which also depend on the experimental parameters.
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