Photopolymerization of 1,2-Epoxypropane by Arenediazonium Salts-A Model System for the Curing of Epoxy Resinsm

AbstractThe post-photolysis polymerization of neat 1,2-epoxypropane by salts of 2,5-diethoxy-4-tolylthiobenzene- diazonium cation has been studied kinetically by viscometric, dilatometric and polymer isolation methods, and the characteristics of the epoxy polymer determined by gel permeation chromatography. The principal features of the polymerization are as follows:(i) fast polymerization (over the first 5 min) gradually slowing up to give the final extent of conversion over 24 h,(ii) conversion to polymer rarely exceeding 30%,(iii) A?w figures of ca. 3 x 104, with ca. 2 - 4, for isolated polymer,(iv) cationic character as evidenced by immediate and total termination by added sodium phenoxide,(v) a very pronounced sensitivity to water,(vi) considerable retardation by “inert” cosolvents such as cyclohexane and 1,2-dichloroethane.A mechanistic scheme is proposed.