Synthesis of Epoxy-Functional Microspheres by Cationic Suspension Photopolymerization

This article describes the development of a novel rapid one-step cationic suspension photopolymerization method for the synthesis of epoxy-functional polymeric microspheres ranging in size from 50 nm to 100 (mu)m. Multifunctional silicon-containing epoxy monomers and oligomers were photopolymerized to produce microspheres in both in aqueous and nonaqueous suspensions using a variety of cationic photoinitiators. Various solvents with controlled polarities were employed to produce macroporous particles. The effects of a variety of experimental and compositional variables on the particle diameter, size distribution, and epoxy content of the microspheres were examined. Among the parameters that were evaluated were the initiator composition and concentration, agitation method, UV irradiation time, viscosities of both the monomer and suspending medium, and type of porogen used. Following synthesis, the microspheres were characterized by SEM microscopy and by titration to determine the epoxy-functional group content. Microspheres that were subjected to pyrolysis at 700 C retained their macrostructure despite undergoing a 60% weight loss.