Organic peroxides. I. Initiation of styrene polymerization

Abstract

Abstract The relationship between peroxide activity for several aliphatic and aromatic peroxides, as given by the respective decomposition rate constants ( k d ), and their influence on the polymerization of styrene at 70°C. is reported. Particular emphasis was placed on studying the role of these peroxides in determining rates and degrees of polymerization ( DP ) and the “efficiency” of these peroxides in the initiation of polymerization. A correlation of peroxide activity could best be made with rates of polymerization. Most of the peroxides studied did not exhibit chain transfer activity, and the DP was a function of the propagation and termination characteristics of the monomer‐polymer radical system. Two chlorinated benzoyl peroxides had considerable chain transfer activity, but this could not be correlated with their decomposition rate constants. Although there was no relationship of peroxide activity to efficiency of initiation, some of these efficiency values appeared to be unreasonably low. The major uncertainty appeared to be the use of published peroxide k d values which were not determined under conditions suitable for use with polymerization data to calculate efficiencies. Where necessary, k d values were redetermined and the final results gave a more suitable basis for comparison of peroxide activities and their influence on polymerization. The use of infrared analysis for determination of peroxide decomposition rate constants is described.