Soluble polyimides with propeller shape triphenyl core for membrane based gas separation

This article reports the synthesis and characterization of a series of new aromatic polyimides (PIs) having bulky tert butyl group containing propeller shaped triphenylamine unit in its structure. The PIs were prepared by the reaction of 4,4-diamino-4-(2,4,6-tri-tert-butylphenoxy) triphenylamine with different commercially available aromatic dianhydrides through the formation of corresponding poly(amic acid)s and subsequent thermal cycloimidization. The PIs showed high glass transition temperature (T-g up to 270 degrees C) and thermal stability (T-d10 up to 475 degrees C). The PI membranes showed good mechanical properties with tensile strength up to 70 MPa, excellent separation performance [P(CO2)=100.8, P(O-2)=40.4 barrer], and good permselectivity [P(CO2)/P(CH4)=50.9, P(O-2)/P(N-2)=7.6]. The membranes exhibited extremely high solubility selectivity for the CO2/CH4 gas pair due to the strong affinity between CO2 and nitrogen atoms of tertiary amine in triphenylamine. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46658.