Fast transient fluorescence technique for determination of gelation activation energies in free-radical cross-linking copolymerization

Gelation during free-radical cross-linking copolymerization (FCC) of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM) was studied using the fast transient fluorescence (FTRF) technique. Pyrene (P_y) was used as a probe for the FTRF experiments. Fluorescence lifetimes of P_y from its decay traces were measured and used to monitor the gelation processes in various EGDM contents at various temperatures. MMA consumption rates were measured during the gelation process by employing the Stern-Volmer kinetic model. Composite rate constants, k_r, for FCC were determined for each EGDM content at different temperatures, and it is observed that as EGDM content and/or temperature is increased k_r increased. Gelation activation energies, ΔE_G, were measured for different EGDM contents, and it is observed that as ΔE_G is decreased the EGDM content is increased.