POLYMETHYLMETHACRYLATE IN MIXED SOLVENTS IV.EQUILIBRIUM SWELLING OF A SLIGHTLY CROSSLINKED POLYMER IN MIXED SOLVENTS

The equilibrium swelling ratios of a slightly crosslinked polymethylmethacrylate sample in toluene-ethanol and acetone-water solvent-non-solvent mixtures have been determined volumitrically. The values of swelling ratio Q go through a maximum at the volume fraction of the non-solvent, γ=0.17 (ethanol) and 0.02 (water) for the two systems respectively,in parallel with the viscometric and osmometric behavior observed in dilute solutions. It was found that the swelling ratio in theta solvent Q_θ is independent of the solvent-non-solvent pair. Thus it is more convenient to compare the swelling behavior in different solvent systems by expressing experimental data in terms of Xswelling = (Q/Q_θ)~(1/3). The solubility parameter of polymethylmethacrylate estimated from the maximum swelling ratio is 10.0 .