Fast transient fluorescence technique for studying sol-gel phase transition in polymeric mixtures

Fast transient fluorescence (FTRF) technique was used to study the sol-gel phase transition in free-radical crosslinking copolymerization of methyl methacrylate (MMA), ethyl methacrylate (EMA) and their mixtures with ethylene glycol dimethacrylate (EGDM). Fluorescence lifetimes of pyrene (Py) from its decay traces were monitored during sol-gel phase transitions. Consumption of MMA and/or EMA in pregel solutions due to gel formation dramatically increased the Py fluorescence lifetimes, in which were used to study the gelation of MMA, EMA and their mixtures as a function of time, at various temperatures and monomer concentrations. Monomer consumption rates, k_r were measured during sol-gel transition process by using Stern-Volmer model. Gelation activation energies ΔE_G were determined and found to be 14 and 10kcalmol^-1 for MMA and EMA respectively.