(733e) Structural Determination, Gas Separation Performance and Related Simulations of Extem® XH1015

Authors: 
Xia, J., National University of Singapore
Liu, S., National University of Singapore
Chung, T., National University of Singapore


By employing high resolution 1H and 13C 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 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. Amorphous Cell and Molecular Dynamic modules are employed as major simulation steps. The FAV values are calculated via Connolly task which employ a hard sphere with a particular diameter as a probe to detect the available vacancy inside an optimized amorphous polymer cell. 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. Relative FAV values are adopted to illustrate the relationship between experimental permeation data and FAV values. Their selectivity differences are also discussed in terms of FAV ratios which give a more visual representation. The FAV concept is proved to be more effective than fractional free volume (FFV) to analyze and predict gas separation performance.

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