Poly(ethylene oxide) (PEO)-containing polymer membranes are attractive for CO2-related gas separations due to their high selectivity toward CO2. However, the development of PEO-rich membranes is frequently challenged by weak mechanical properties and a high crystallization tendency of PEO that hinders gas transport. Here we report a new series of highly CO2-selective, amorphous PEO-containing segmented copolymers prepared from commercial Jeffamine polyetheramines and pentiptycene-based polyimide. The copolymers are much more mechanically robust than the nonpentiptycene containing counterparts due to the molecular reinforcement mechanism of supramolecular chain threading and interlocking interactions induced by the pentiptycene structures, which also effectively suppresses PEO crystallization leading to a completely amorphous structure even at 60% PEO weight content. Membrane transport properties are sensitively affected by both PEO weight content and PEO chain length. A nonlinear correlation between CO2 permeability with PEO weight content was observed due to the competition between solubility and diffusivity contributions, whereby the copolymers change from being size-selective to solubility-selective when PEO content reaches 40%. CO2 selectivities over H2 and N2 increase monotonically with both PEO content and chain length, indicating strong CO2-philicity of the copolymers. The copolymer film with the longest PEO sequence (PEO2000) and highest PEO weight content (60%) showed a measured CO2 pure gas permeability of 39 Barrer, and ideal CO2/H2 and CO2/N2 selectivities of 4.1 and 46, respectively, at 35 °C and 3 atm, making them attractive for hydrogen purification and carbon capture.

2A series of polybenzimidazoles containing sulfonyl groups were synthesized in 3 Eaton's reagent for high temperature H 2 /CO 2 separation membranes. The key 4 monomer, 3,3',4,4'-tetraaminodiphenylsulfone, was prepared via a novel and 5 economical synthetic route starting from 4,4'-dichlorodiphenylsulfone. These 6 polybenzimidazoles with sulfonyl moieties had enhanced solubilities in dipolar 7 aprotic solvents relative to the commercial Celazole ® that is prepared from 8 diaminobenzidine. Thermal gravimetric analysis showed that the materials were stable 9 at elevated temperatures with 5% weight loss values of at least 485 o C in either air or 10 N 2 . Glass transition temperatures of three polybenzimidazoles in this series were 11 ascertained by dynamic mechanical analysis to be 438-480 o C. These sulfonyl-12 containing polybenzimidazoles exhibited excellent gas separation properties for 13 H 2 /CO 2 . Polymers from tetraaminodiphenylsulfone and either terephthalic or 14 isophthalic acid crossed Robeson's upper bound for H 2 /CO 2.

For the first time, a theoretical analysis of gas sorption, based on the non-equilibrium lattice fluid (NELF) model, in chemically-imidized HAB-6FDA polyimide and its thermally rearranged analogs is presented. Due to the inaccessibility of pVT data in the rubbery region, the characteristic lattice fluid parameters of the polymers considered in this study were obtained from a collection of infinite dilution solubility data at multiple temperatures. Hydrogen, nitrogen and methane sorption isotherms at 35°C were fit to the NELF model using one adjustable parameter, i.e., the polymer-penetrant binary interaction parameter, 12 k . The optimal value of 12 k for each polymer-penetrant pair was used to predict hydrogen, nitrogen and methane sorption isotherms at other temperatures and at pressures up to 6 MPa. For carbon dioxide, a second adjustable parameter, the swelling coefficient, was introduced to account for sorption-induced matrix dilation. The ideal solubility-selectivity is also predicted for several gas pairs. The increase in gas sorption in thermally rearranged samples relative to their polyimide precursor is essentially due to entropic effects, i.e., to the increase in non-equilibrium fractional free volume during thermal rearrangement.

Thermally rearranged (TR) polymers have been the subject of many fundamental studies, but the effect of TR conversion on temperature-dependent transport properties is largely unexplored. Sorption isotherms for N 2 , CH 4 , and CO 2 in HAB-6FDA polyimide and its TR analogs were measured at temperatures ranging from-10 °C to 50 °C and pressures up to 27 atm. Solubilities increase with decreasing temperature for each gas and sample tested. At low TR conversions, the sorption process initially becomes less exothermic. However, enthalpies of sorption do not significantly change with TR conversion after the initial stages of rearrangement. Enthalpies of sorption in TR polymers are qualitatively similar to those of other high free volume materials. Solubility selectivity for CO 2 /CH 4 at 10 atm did not change with temperature due to similar enthalpies of sorption for CO 2 and CH 4. Sorption data were fit to the dual mode model at different temperatures, and model parameters were correlated with polymer and penetrant properties.