Effect of comonomer concentration and functionality on photopolymerization rates, mechanical properties and heterogeneity of the polymer

Abstract

Polymerization rate, glass transition temperature, storage modulus, molecular weight between crosslinks and heterogeneity of the final polymer product were studied as a function of the crosslinking agent concentration for several multifunctional methacrylates. The goal of this study was to determine the effect of crosslinking monomer structure and concentration on the rates of polymerization and mechanical properties of the polymer. A series of copolymers with equal concentrations of crosslinking double bonds was prepared using a monomethacrylate plus a di- or trimethacrylate. The trimethacrylate systems had higher glass transition temperatures, larger storage moduli, and smaller molecular weights between crosslinks than the comparable dimethacrylate systems. However, the heterogeneity of the trimethacrylate systems was found to be much more extensive. Additionally, the maximum rate of polymerization was found to increases with increasing crosslinking agent when octyl methacrylate was used as the monomethacrylate, but passed through a maximum when 2-hydroxyethyl methacrylate was used. The relative rates of polymerization between the trimethacrylate and dimethacrylate systems also depended on the monomethacrylate employed and the concentration of the crosslinking agent.