Dissolution rates of poly(methyl methacrylate) films in mixed solvents

A laser interferometer has been used to measure in situ the dissolution rates of thin films of poly(methyl methacrylate) (PMMA). The most significant finding is that addition of small amounts of a low‐molecular weight nonsolvent can increase the rate obtained with a higher molecular weight solvent. In this study, silicon wafers were coated with polymer (about 1 μm thick) and annealed at 155°C for 1 h. The dissolution rates were measured at 17.5, 22.5, and 27.5°C. All the mixtures contained methyl ethyl ketone (MEK) (2‐butanone), as the major component. The minor component was water, methanol, ethanol, 1‐propanol, 2‐propanol, or ethylene glycol. Water and methanol showed the greatest effects. Both were able to increase the dissolution rate as much as two‐fold. All the mixtures exhibit the same activation energy (25 kcal/mol) despite their wide differences in dissolution rate.