SORPTION, DILATION, AND ISOTHERMAL GLASS-TRANSITION OF POLY(ETHYL METHACRYLATE)-ORGANIC GAS SYSTEMS

Sorption of ethylene, ethane, and propane into poly(ethyl methacrylate) and the concomitant dilation of the polymer are measured at 15-degrees-C. Each sorption isotherm has a reverse-sigmoid shape described by the extended dual-mode sorption model, and dilation isotherms are similar in shape to the corresponding sorption isotherms. Inflection on the isotherms is due to isothermal glass transition induced by the sorbed gases, whose concentration is the glass transition concentration C(g). The C(g) value for propane is in accord with concentration at an abrupt change found on a curve of the concentration dependence of diffusivity. Partial molar volumes of the gases at rubbery state and glassy state are evaluated from sorptive dilation data above and below C(g), respectively. A correlation between plasticizing ability and partial molar volume for the gases is discussed.