Fluorescence Method to Study Swelling Phenomenon in Poly(methyl methacrylate) Gels

Authors: Yaşar YILMAZ, Önder PEKCAN

Abstract: Gelation during solution free radical crosslinking copolymerization \-(FCC) of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM) was studied by using steady state fluorescence technique. FCC was performed in the presence of toluene at 75 ^\circC. Sol-Gel phase transition were monitored by observing the direct intensity of an excited pyrene (Py) during in situ fluorescence experiments for various toluene content. After drying these gels, swelling and desorption experiments were performed in toluene at 50 ^\circC by real-time monitoring of Py fluorescence intensity in disc shape gels. 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 paramaters. Cooperative diffusion coefficents (D_c) were measured and found to be around 10^{-6} cm^2/sec for gels swolen in toluene. It was also oabserved that loosely formed gels swell much faster than densely formed gels.

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