Copolymerization of Epoxides with Cyclic Anhydrides Catalyzed by Tertiary Amines in the Presence of Proton-Donating Compounds

Abstract

This paper deals with the copolymerization of epoxide [2-hydroxy-4-(2,3-epoxypropoxy)benzophenone] with cyclic anhydride (phthalic anhydride) catalyzed by tertiary amine (tri-n-hexylamine) in the presence of proton-donating compounds in o-xylene solution at 393°K (120°C). On the basis of kinetic investigations performed in the presence of benzoic acid, a reaction scheme has been put forward for the copolymerization. This scheme involves the assumption that the primary active center of ionic character may arise by interaction of acid with amine as well as by initiation mechanism in the absence of proton-donating compound. In the growth stage, alternating reactions of the carboxylate or alkoxide reaction center with epoxide or anhydride take place to give polyester. The termination involves a mono-molecular decomposition of the active centers giving rise to intermediates with alcoholic and carboxylic terminal groups which participate again in reinitiation of the copolymerization. By comparing the effect of different proton-donating compounds of various types (alcohol, phenol, or acid), it may be deduced that the acceleration of copolymerization depends not only on the proton-donating power of the compound but also on its behavior in esterification reactions