High-performance membranes from polyimides with intrinsic microporosity

The synthesis of three high-performance polyimides membranes using a bis(carboxylic anhydride), derived from monomer with intrinsic microporosity, was described. The adsorption isotherms show high uptake at very low relative pressure, as is characteristic of a microporous material. It is noted that the rate of nitrogen uptake at 77K is slow for polymer materials such as that of PIM-PI-3. The solution-diffusion model of polymer membranes show that the selectivity may be expressed in terms of the solubility and diffusion coefficients for each components. The effect of the high solubility coefficients pf glassy polymers is to enhance gas permeability without loss of selectivity. The high solubility coefficients of polymers is attributed to a combination of microporous character, which enhances uptake.