The polymerization of styrene sensitized by molecules in the triplet state II. Kinetics and mechanism

The kinetics and mechanism of the reaction between anthracene and styrene have been fully investigated. By means of flash photolysis techniques, it has been confirmed that it is the triplet state of anthracene which sensitizes the polymerization. It has also been shown that both triplet and unexcited singlet anthracene copolymerize with styrene, the former with a zero activation energy. The work has been extended to the polymerizations sensitized by pyrene and chrysene, and to the unsensitized photopolymerization of styrene. It has been shown that in every case an initiation mechanism, involving the initial formation of a triplet-monomer complex, satisfactorily explains the observed results. The copolymerization rates of pyrene and chrysene were undetectable; these results, coupled with those obtained for the copolymerization of anthracene with styrene, are in agreement with the conclusions of Kooyman & Farenhorst, Szwarc, and others, concerning the reactivity of olefinic and aromatic hydrocarbons to radical addition. Finally, a qualitative investigation of the photochemical reactions between the sensitizers, and cumene and 9 .10-dihydroanthracene, has been made.