Blends of a Polymer of Intrinsic Microporosity and Partially Sulfonated Polyphenylenesulfone for Gas Separation

Polyphenylenesulfone (PPSU) and sulfonated polyphenylenesulfone (sPPSU) are widely used for liquid separations in the medical and food industries. However, their potential applications for gas separation have not been studied extensively owing to their low intrinsic gas permeability. We report here for the first time that blending with sPPSU can significantly improve the gas separation performance of highly permeable polymers of intrinsic microporosity (PIMs), specifically PIM-1, because of the strong molecular interactions of the sulfonic acid groups of sPPSU with CO2 and O-2. In addition, a novel co-solvent system has been discovered to overcome the immiscibility of these polymers. The presence of a higher degree of sulfonation in sPPSU results in better gas separation performance of the blend membranes close to or above the Robeson upper bound lines for O-2/N-2, CO2/N-2 and CO2/CH4 separations. Interestingly, the blend membranes have comparable gas selectivity to sPPSU even though their sPPSU content is only 5-20wt%. Moreover, they also display improved anti-plasticization properties up to 30atm (3MPa) using a binary CO2/CH4 feed gas. The newly developed PIM-1/sPPSU membranes are potential candidates for air separation, natural gas separation, and CO2 capture.