The thermal degradation of three polymeric peroxides of styrene monomers with substituents in the para position was studied at various temperatures (65, 75, 85, and 95°C). A continuous distribution model was used to evaluate the rate coefficients for the random-chain and chain-end scission degradation from the evolution of molecular weight distributions with time. The activation energy determined from the temperature dependence of the rate coefficients was in the range 18-22 kcal mol-1. This result suggests that the thermal degradation of polyperoxide is controlled by the dissociation of the O - O bonds in the polymer backbone. The thermal stability for poly(p-methylstyrene peroxide) lies in between that of poly(p-tert-butylstyrene peroxide) (highest) and poly(p-bromostyrene peroxide) (lowest).
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