Experimental determination of gelation and swelling parameters using time-resolved fluorescence technique

A fast transient fluorescence (FTRF) technique was used to study the sol-gel transition during gelation of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM). Pyrene (Py) was used as a fluorescence probe for the in situ polymerization experiments. Swelling of this cylindrical poly(methyl methacrylate) (PMMA) gel in chloroform was monitored using FTRF technique. Fluorescence lifetimes of Py from its decay traces were measured and used to monitor both the gelation and swelling processes. Stern-Volmer kinetics were employed to determine the quenching rate constant before the onset of gelation. MMA consumption rate was measured during gelation process using the Stern-Volmer model. A Li-Tanaka equation was introduced to determine the cooperative diffusion coefficient D_c, which was found to be around 10^-5 cm² s^-1 during the swelling of PMMA gel in chloroform.