TEMPERATURE-DEPENDENCE OF INITIATION REACTIONS OF OXYGEN-CENTERED RADICALS

The temperature dependence of initiation reactions of t-butoxy, cumylo xy, and benzoyloxy radicals, was studied using 2,4-diphenyl-4-methyl-1 -pentene (alpha-methylstyrene dimer, MSD) as a model compound of styre ne and a radical trapping agent. The ratios between addition of the ox y radicals to MSD and their self-decomposition (beta-scission or decar boxylation) were found to greatly depend on the reaction temperature. The differences in activation energy between self-decomposition and ad dition (E-d-E-a) for t-butoxy, cumyloxy, and bezoyloxy radicals were e stimated to be 7.8, 7.9, and 5.0 kcal mol(-1), respectively. End group ratios (t-butoxy/methyl, cumyloxy/methyl, and benzoyloxy/phenyl) for polystyrene obtained by initiation of the oxy radicals are simulated o ver the temperature range 50-150 degrees C.