The gas separation performance adjustment of carbon molecular sieve membrane depending on the chain rigidity and free volume characteristic of the polymeric precursor. (March 2019) - Hu, Chun-Po
Abstract: Carbon molecular sieve membranes (CMSMs) are regarded as promising membranes for gas separation due to its high gas separation performance. Polyimide (ODPA-FDA) precursor films were prepared and characterized for the formation of carbon molecular sieve membranes. This was compared to a commercial polyimide Matrimid. The precursor membranes were characterized with dynamic mechanical analysis, thermogravimetric analysis, X-ray diffraction, FTIR spectroscopy, positron annihilation lifetime spectroscopy in order to determine the effect of the polyimide structure on its permeation properties. The carbonized membranes were characterized by determining its pore size distribution and sorption isotherms. Results showed that ODPA-FDA polyimide has a higher Tg and d-spacing than that of Matrimid. The permeability and selectivity of ODPA-FDA precursor and carbonized films were higher or similar than that of Matrimid precursor and carbonized films due to the addition of a bulky aromatic group in the ODPA-FDA amine moiety which causes narrow free volume distribution. The unique structure of ODPA-FDA polyimide makes it an attractive candidate for the precursor of CMSM. Graphical abstract: Highlights: ODPA-FDA polyimide with rigid molecular chain was synthesized. Precursor with rigid molecular chain shows narrower free volume distribution. Gas separation properties of CMSM made from ODPA-FDA PI is better than Matrimid.