Carbon dioxide sorption in conventional and plasma polymerized methyl methacrylate thin films

CO2 sorption isotherms are reported for plasma polymerized methyl methacrylate (ppMMA) and the conventionally polymerized analog, poly(methyl methacrylate) (PMMA). The isotherms are measured at temperatures ranging from 20 to 95 °C and analyzed using the Dual-Mode sorption model. In the lower temperature range, the magnitude of the Henryʹs law (kD) and the coupled Langmuir component parameters (C′Hb) for both materials are similar. The expected collapse of the Langmuir sorption mode in conventional PMMA near the glass transition temperature is clearly observed. However, the Langmuir component in the plasma polymerized material does not diminish in the same manner as that for the conventional polymer analog. In contrast with the ppMMA, the PMMA materials are shown to exhibit significant dilation for extended conditioning times at high CO2 pressures. The response of the isotherms for the two materials to ‘quench’ and ‘slow cool’ thermal conditioning protocols are similar, but small.