Gels were swollen in various solvents with different molar volume V and solubility parameter delta. In situ steady state fluorescence (SSF) measurements were performed for swelling experiments in gels formed by free radical crosslinking copolymerization (FCC) of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM). Gels were prepared at 75 degreesC with pyrene (Py) as a fluorescence probe. After drying these gels, swelling and slow release experiments were performed in various solvents with different V and delta at room temperature by time monitoring of the Py fluorescence intensity. The Li-Tanaka equation was used to produce time constant tau (1) values. Cooperative diffusion coefficients (D-c) were measured and found to be strongly correlated to the molar volume of the solvents used. Solvent uptake and degree of swelling were found to be dependent on the solubility parameter of the solvent. (C) 2000 Society of Chemical Industry.