In situ fluorescence experiments to study swelling and slow release kinetics of disc-shaped poly(methyl methacrylate) gels made at various crosslinker densities

In situ steady state fluorescence (SSF) measurements are performed for studying swelling and slow release processes in gels formed by free radical crosslinking copolymerization (FCC) of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM). Gels were prepared at 80°C for various EGDM contents with pyrene (Py) as a fluorescence probe. After drying these gels, swelling and slow release experiments were performed in chloroform at room temperature by real-time monitoring of the Py fluorescence intensity. A correction method was developed to obtain pure swelling curves, by using desorption curves of Py molecules. The Li-Tanaka equation was employed to produce swelling parameters. Cooperative diffusion coefficients (D_c) were measured and found to be around 2×10^-5 cm²/s for gels swollen in chloroform. Slow release diffusion coefficients (D) were measured using the classical diffusion equation and found to be around 8×10^-5 cm²/s.