Synthesis and properties of soluble poly[bis(benzimidazobenzisoquinolinones)] based on novel aromatic tetraamine monomers

Four aromatic tetraamine monomers possessing flexible ether linkages were successfully synthesized by nucleophilic aromatic substitution of hydroquinone, 4,4′-dihydroxybiphenyl, 2,2′-bis(4-hydroxyphenyl)propane, and 2,7-dihydroxynaphthalene with 5-chloro-2-nitroaniline, followed by reduction, respectively. With these monomers, a new class of soluble poly[bis(benzimidazobenzisoquinolinones)] was prepared by a one-step, high-temperature solution polycondensation. The resulting polymers were completely soluble in phenolic solvents and had high inherent viscosities ranging from 1.2 to 1.5 g dL−1. These polymers had glass transition temperatures in the range of 427–449 °C. Thermogravimetric analysis showed that all polymers were thermally stable, with 5% weight loss recorded above 510 °C in nitrogen. The tough polymer films, obtained by casting from solution, had tensile strength, elongation at break, and tensile modulus values in the range of 79.5–114.5 MPa, 10.3–23.0%, and 1.1–1.7 GPa, respectively. It is demonstrated that these semiladder polymer membranes displayed high CO2 permeability coefficients ( P CO 2 = 31.6 − 96.5 barrer ) and permeability selectivity of CO2 to CH4 ( P CO 2 / P CH 4 = 30.6 − 43.4 ) .