Synthesis and Characterization of Novel Homopolyimides Containing Pyridine and Morpholine Groups for Gas Separation by Molecular Design and Simulation

摘要

A novel 4-(4-(1-morpholinyl)phenyl)-2,6-bis(4-aminophenyl)pyridine (MPAP) diamine monomer was designed and synthesized by introducing non-coplanar morpholine groups and pyridine heterocyclic structures. By one-step homopolymerization of MPAP and different dianhydrides, three new polyimides (PIs) were synthesized. The obtained PIs are easily soluble in common organic solvents, such as NMP, DMAc, and CHCl3. Simultaneously, PIs have high thermal performance (Tg = 277-377 degrees C) and excellent thermal stability (Td,5% and Td,10% are 460-487 degrees C and 525-545 degrees C). They also have good optical transparency (lambda cutoff = 380-394 nm, lambda 80% = 469-482 nm) and hydrophobicity (theta = 87-92o). The free volume and gas adsorption are simulated by Materials Studio 2019 software, and the simulation results match the gas separation performance obtained from experimental test. They show good gas separation performance as well, especially PI-3 for the CO2/N2 (up to 23.26), O2/N2 (up to 5.02) and He/N2 (up to 59.78) separations, which is close to the 1991 Robeson upper bound.

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