Hongchao Mao

Synthesis, characterization and gas transport properties of novel poly(amine-imide)s containing tetraphenylmethane pendant groups

Two bis(amine anhydride) monomers containing tetraphenylmethane pendant groups were synthesized from the palladium-catalyzed amination reaction of N-methyl-4-chlorophthalimide with different arylamines, followed by alkaline hydrolysis of the intermediate bis(amine-imide)s and subsequent dehydration of the resulting tetraacids. These monomers were polymerized with the appropriate aromatic diamines to obtain a series of novel poly(amine-imide)s. The obtained polymers exhibited good solubility in many aprotic solvents and had glass transition temperatures in the range of 310 to 395 °C. Thermogravimetric analysis showed that all of the polymers were stable, with 10% weight loss recorded above 510 °C under nitrogen. The surface areas of these novel poly(amine-imide)s ranged from 78 to 290 m2 g−1. Films obtained by casting exhibited a combination of relatively high permeability and modest to good permselectivity with values close to Robeson’s upper bound limit for O2/N2 and CO2/CH4 gas pairs.

Mixed-matrix membranes incorporated with porous shape-persistent organic cages for gas separation

There has been much recent interest in the use of porous materials derived from self-assembling, shape-persistent organic cages due to their solubility and easy post-synthetic modification. Herein we report the preparation of novel mixed-matrix membranes (MMMs) employing the porous organic cage Noria and its derivatives Noria-Boc and Noria-COtBu as the fillers, and a fluorine containing polyimide, 6FDA-DAM, as the polymeric matrix. The physical structures and properties of Noria and its derivatives were measured and investigated. Noria with substituents of Boc (cleaved by thermal treatment during the process of membrane fabrication) and COtBu groups tend to show much better compatibility with polyimide than Noria itself, resulting in homogeneous dispersion of nanoaggregates and fine adhesion between the two phases in the derived Noria/6FDA-DAM and Noria-COtBu/6FDA-DAM MMMs. Gas permeation tests revealed that Noria and Noria-COtBu nanoparticles have different effect on gas separation performance of MMMs. The introduction of Noria into 6FDA-DAM tends to enhance CO2/CH4 selectivity and thus improve its gas separation properties, though a decrease in the observed permeability could be observed. In contrast, the introduction of Noria-COtBu with higher surface area and larger pores tends to increase the free volume and gas permeability of MMMs. These results show that both the morphology and the gas separation properties of MMMs could be tuned by tailoring the structures of porous organic cages.