Slow release of trapped homopolymers from a swelling polymeric gel: A fluorescence study
In-situ steady-state fluorescence experiments were performed for studying slow release of pyrene-labeled polystyrene chains from polystyrene gels formed by free-radical crosslinking copolymerization. Atom transfer radical polymerization was used to produce the pyrene end-capped polystyrene chains. In order to load the pyrene end-capped polystyrene chains into the gel disc-shaped gels were left in toluene solutions of pyrene end-capped polystyrene chains of various molecular weights. These swollen gels were redried in air and then immersed in pure toluene solution for monitoring slow release from the gel. These reswelling experiments were performed at room temperature in real time by monitoring the pyrene emission intensity using steady-state fluorescence measurements. Slow-release diffusion coefficients were measured and found to decrease as the crosslink density of the gels increased. It was observed that higher molecular weight pyrene end-capped polystyrene chains released much faster than low molecular ones during the slow-release process.