Modeling of swelling by fluorescence technique in poly (methyl methacrylate) gels

A novel technique based on in-situ steady-state fluorescence (SSF) measurements is introduced for studying swelling processes in gels formed by free radical cross-linking copolymerization (FCC) of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM) in toluene. Gels were prepared at 75°C for various toluene contents with pyrene (Py) as a fluorescence probe. After drying these gels, swelling and desorption experiments were performed in toluene at 50°C by real-time monitoring of Py fluorescence intensity. A correction method was developed to obtain pure swelling curves, by using desorption curves of Py molecules. Li-Tanaka equation was employed to produce swelling parameters. Cooperative diffusion coefficients (D_c) were measured and found to be around 10^-6 cm²/s for gels swollen in toluene.