Novel latent initiator for cationic polymerization of epoxides

A novel latent initiator for cationic polymerization of epoxides, a composite catalyst containing aluminum complexes and phenol derivatives protected with tert-butoxycarbonyl groups (tBOC), is reported. At a certain temperature, protected phenols generate the parent phenols which are coinitiators with aluminum complexes. The deprotection temperature of the tBOC group depends on the structure of the phenol moieties. Bis(p-t-butoxycarbonyloxyphenyl)sulfone (Ph1) generates (p-dihydroxyphenyl)sulfone (PhH1) at around 150°C, the temperature at which the curing of epoxides is conventionally carried out. The thermally generated PhH1 and aluminum complexes initiate the curing of epoxides. Epoxy resin compositions containing these composite catalysts have a long shelf life at room temperature and are cured at around 150°C, showing that the composite catalyst has excellent latent properties.