Modeling of swelling by the fast transient fluorescence technique in a polymeric gel

The time-resolved, fast transient fluorescence technique, which uses a stro be master system, was employed for studying the swelling of a disc-shaped p oly(methyl methacrylate) gel. The disc-shaped gel was prepared by free-radi cal copolymerization of methyl methacrylate and ethylene glycol dimethacryl ate. Pyrene (Py) was introduced as a fluorescence probe during polymerizati on. After this gel was dried, swelling and slow-release experiments were pe rformed in chloroform at room temperature. Lifetimes of Py were measured du ring in situ swelling and slow-release experiments. An equation was derived for low-quenching efficiencies to interpret the behavior of lifetimes in a nd out of the gel during swelling. Py lifetimes in the gel decreased as swe lling proceeded, but Py lifetimes out of the gel stayed constant during the slow-release experiments. The Li-Tanaka equation was used to determine the cooperative and mutual diffusion coefficients, which were around 10(-5) an d 10(-7) cm(2)s(-1), respectively. (C) 2000 John Wiley & Sons, Inc.