Abstract

The synthesis of PIM-1 is reported from stepgrowth polymerizations of 5,5′,6,6′-tetrahydroxy-3,3,3′,3′tetramethyl-1,1′-spirobisindane with the commercially cheaper monomer, tetrachloroterephthalonitrile. Nitrogen-purged polymerizations (100−160 °C) were quenched after a monitored increase in viscosity. A combination of multiple detector size exclusion chromatography, nuclear magnetic resonance, matrix-assisted laser desorption/ionization-time of flight (MALDI TOF) mass spectrometry, dynamic light scattering, and elemental analysis was used to elucidate significant structural differences (cyclic, branched, tadpole, extended, and network topologies) in the polymers produced under different conditions. A significant proportion of the apparent surface area (up to 200 m 2 g −1 ) associated with PIM-1 can be attributable to whether its contorted polymer chains in fact link to form cyclic or other nonlinear structures. Membranes cast from solutions of polymer samples containing higher branching and network contents exhibited higher gas pair selectivities (CO 2 /CH 4 and CO 2 /N 2 ), above the Robeson 2008 upper bound. A toolbox approach to the characterization and production of topologically different PIM-1 samples has been developed which can be used to tune membrane performance for gas separation and other applications.

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A new series of thin film composite membranes with high CO2 permeance (up to 8000 GPU) and CO2/N2 selectivity (up to 55.7) was designed and fabricated via coating PIM-1 solution in a mixture of chloroform and trichloroethylene on top of a cross-linked PTMSP gutter layer.