By employing high resolution 1 H and 13 C NMR spectroscopy combined with elemental analysis and FTIR-ATR, we have determined the basic chemical structure of Extem XH 1015, a new brand of polyetherimide with good thermal, mechanical properties, and processability. Bisphenol-A dianhydride (BPADA) and diamino diphenyl sulfone (DDS) are found to be the monomers for this newly developed polyetherimide. The gas permeability of this new polymer is reported for the first time in the literature. Polysulfone (PSU) and Ultem are employed as reference samples for the elucidation of permeability and selectivity differences among them because of their structural similarities. In addition to qualitative comparison of chain rigidity and packing with gas transport properties, computational simulations powered by Material Studio are performed at a molecular level to quantitatively investigate the relationship between the fractional accessible volume (FAV) and gas permeability. The FAV differences among these polymers increase with an increase in gas molecules diameters; thus these polymers have similar permeability for small gas molecules but diverse for large gas molecules. Their selectivity differences are also discussed in terms of FAV ratio. The FAV concept is proved to be more effective than fractional free volume to analyze and predict gas separation performance.

An effective separation of CO2 from H2 can be achieved using currently known polyethylene oxide (PEO)‐based membranes at low temperatures but the CO2 permeability is inadequate for commerical operations. For commercial‐scale CO2/H2 separation, CO2 permeability of these membranes must be significantly enhanced without compromising CO2/H2 selectivity. We report here exceptional CO2/H2 separation properties of a nanohybrid membrane comprising polyethylene glycol methacrylate (PEGMA) grafts on an organic‐inorganic membrane (OIM) consisting of a low molecular weight polypropylene oxide (PPO)‐PEO‐PPO diamine and 3‐glycidyloxypropyltrimethoxysilane (GOTMS), an alkoxysilane. The CO2 gas permeability of this nanohybrid membrane can reach 1990 Barrer with a CO2/H2 selectivity of 11 at 35 °C for a mixed gas mixture comprising 50% CO2 ‐ 50% H2 at 3.5 atm. The transformation of the inorganic silica phase from a well‐dispersed network of finely defined nanoparticles to rough porous clusters appears to be responsible for this OIM membrane exceeding the performance of other state‐of‐the‐art PEO‐based membranes.

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This paper introduces a novel method to improve CO2 permeability and CO2/light gas permselectivity by adding poly(ethylene glycol) (PEG) into the PEG–silica organic–inorganic hybrid matrix. The matrix is cross-linked by in-situ formation of silica nanoparticles with diameters ranging from 1 to 5 nm. These particles disperse homogenously in the organic phase according to the morphology studied by scanning TEM. Much small particles were evolved after blending PEG into the matrix due to more fraction of bifunctional and trifunctional silicon containing groups. Four PEGs with different molecular weights (M w = 400, 1000, 1500, and 2000 g/mol) are added into the matrix prior to the matrix formation. Permeability coefficients of three pure gases (H2, N2, and CO2) and one mixed gas (CO2/N2) are measured to explore the effects of PEG content and molecular weight on the gas transport properties. The membrane containing 60 wt % of 1000 g/mol PEG could achieve an ultrahigh CO2 permeability of 845 barrer with CO2/H2 and CO2/N2 permselectivity around 10 and 40, respectively. Fundamental studies on the effect of temperature on gas diffusivity and solubility are also carried out. Molecular weights of PEGs have been proved to play a crucial role in determining the permeability and diffusivity.