IN-SITU FLUORESCENCE EXPERIMENTS TO STUDY SWELLING AND SLOW-RELEASE KINETICS OF DISC-SHAPED POLY(METHYL METHACRYLATE) GELS MADE AT VARIOUS CROSS-LINKER DENSITIES

In situ steady state fluorescence (SSF) measurements are performed for studying swelling and slow release processes in gels formed by free r adical crosslinking copolymerization (FCC) of methyl methacrylate (MMA ) and ethylene glycol dimethacrylate (EGDM). Gels were prepared at 80 degrees 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 monitor ing of the Py fluorescence intensity. A correction method was develope d to obtain pure swelling curves, by using desorption curves of Py mol ecules. The Li-Tanaka equation was employed to produce swelling parame ters. Cooperative diffusion coefficients (D-c) were measured and found to be around 2x10(-5) cm(2)/s for gels swollen in chloroform. Slow re lease diffusion coefficients (D) were measured using the classical dif fusion equation and found to be around 8x10(-5) cm(2)/s. (C) 1998 Else vier Science Ltd. All rights reserved.