Thermal properties of polymer with intrinsic microporosity membranes

The thermal behavior of a polymer with intrinsic microporosity (PIM-1) membrane was investigated via thermomechanical analysis and differential scanning calorimetry. The coefficient of thermal expansion (CTE) was almost constant at 70*106 K−1 below 110 °C and inflection points were observed over the range 120–150 °C, regardless of the fabrication conditions. The CTE after the inflection point strongly depended on the membrane formation conditions and the thermal history. Although the CTE increased with a methanol treatment, the CTE of other membranes decreased because of shrinkage attributed to internal stress. This behavior indicated cooperative molecular motion below 200 °C. In the calorimetry measurements, a specific-heat discontinuity from the glass transition was not observed. However, an extremely broad endothermic peak, which may have been caused by enthalpy relaxation, was observed for a membrane that exhibited advanced physical aging.