IN-SITU FLUORESCENCE EXPERIMENTS TO TEST THE RELIABILITY OF RANDOM BOND AND SITE BOND PERCOLATION MODELS DURING SOL-GEL TRANSITION IN FREE-RADICAL CROSS-LINKING COPOLYMERIZATION

Sol-gel phase transition during the free-radical crosslinking copolyme rization of methyl methacrylate and ethylene glycol dimethacrylate was studied using the steady-state fluorescence method. Copolymerization was performed both in the absence and presence of toluene at 75 degree s C. Sol-gel phase transitions were monitored by observing the direct intensity of an excited pyrene methyl pivalate during in situ fluoresc ence experiments. Random bond and site bond percolation models were em ployed to quantify the results of bulk and solution polymerizations, r espectively, during the sol-gel phase transition. Gel points were dete rmined and the beta exponents were found to be around 0.37 and 0.38 du ring gelation in bulk and solution polymerizations, respectively. Copy right (C) 1996 Elsevier Science Ltd.