Aninsitustudy of dissolution and swelling behavior of polyhyphen;(methyl methacrylate) thin films in solvent/nonsolvent binary mixtures

摘要

A singlehyphen;element rotatinghyphen;polarizer ellipsometer (psihyphen;meter) was used forinsitucharacterization of the thermodynamic and kinetic behavior of polyhyphen;(methyl methacrylate), PMMA, thin films (1.2 mgr;m) in solvent/nonsolvent binary mixtures of methyl ethyl ketone/isopropanol (MEK/IPA) and methyl isobutyl ketone/methanol (MIBK/MeOH). Thermodynamic effects were inferred from equilibrium behavior by the degree of swelling and polymerhyphen;solvent solubility. A sharp transition between complete solubility and almost total insolubility was observed in a narrow concentration range near 50:50 (by volume) solvent/nonsolvent for both MEK/IPA and MIBK/MeOH. In the insoluble regime, the polymer was found to swell up to three times the initial thickness. At 50:50 MEK/IPA, a temperature decrease from 24.8 to 18.4thinsp;deg;C caused a change from complete dissolution to combined swelling/dissolution behavior and rendered the PMMA film only 68percnt; soluble. Kinetic effects were determined by dissolution and penetration rate measurements. A constant penetration velocity was observed for almost all compositions for both binary solvent mixtures with Case II transport assumptions providing good agreement with experimental results. For MEK/IPA, penetration rates increased with increasing MEK concentration. For MIBK/MeOH, however, a maximum was observed at 60:40 MIBK/MeOH.