A KINETIC-STUDY OF DIACRYLATE PHOTOPOLYMERIZATIONS

The kinetics of u.v. photopolymerizations of multifunctional monomers were investigated using poly(ethylene glycol) diacrylates as model systems. The effect of monomer chain length on reaction kinetics was investigated. Results showed that the diacrylate photopolymerizations were extremely rapid. An increase in light intensity caused an increase in the attained conversion. An increase in monomer chain length caused an increase in conversion due to the increase in the diffusivity of the pendant double bonds. A strong autoacceleration effect was also observed at the start of the reaction, indicating the absence of a steady-state radical population. The termination step behaviour was studied by performing dark reactions in which the initiation was halted and the reaction rate was followed. It was shown that a distribution of radical lifetimes exists during the polymerization process, indicating the heterogeneous nature of the final networks.