Dissolution rates for thin films of miscible polymer blends

The dissolution rates of thin polymer films were measured and compared Mixtures of various ratios of poly(methyl methacrylate), PMMA, and poly(p-hydroxystyrene), PPHS, were dissolved in methyl isobutyl ketone, MIBK. The polymer solutions were then spun into thin films on silicon wafers and dried. The films were then placed in an MIBK bath and the rate of dissolution was observed using a laser interferometry apparatus. The results showed pure PPHS films to have dissolution rates one thousand times greater than films of pure PMMA at comparable molecular weights. However, for films containing both PPHS and PMMA, a minimum dissolution rate occurs at a mixture of about 20% (by weight) PPHS.