02309nas a2200229   4500008004100000022001400041245010400055210006900159260007300228300001200301490000800313520146100321653001401782653001901796653002201815653001301837653002201850100002801872700002501900700002201925856013201947       2006                        eng d  a0376-738800aEnhancement of gas permeation properties of polybenzimidazoles by systematic structure architecture0 aEnhancement of gas permeation properties of polybenzimidazoles b  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcDEC  a161-1690 v2863 a<p>Systematic structural variations in thermally stable polybenzimidazole (PBI) are explored that led to a substantial improvement in gas permeation properties. Physical property determinations revealed that incorporation of hexafluoroisopropylidene and tert-butyl groups led to amorphous polymers with slightly lowered thermal stability and decreased chain packing. PBI based on 4,4'-(hexafluoroisopropylidene)bis(benzoic acid) and 5-tert-butyl isophthalic acid exhibited 10-40 times higher permeability, while changes in selectivities for industrially important pairs ranged from modest decrease of 75% or less than that of PBI based on isophthalic acid. The O-2/N-2 selectivity was almost doubled in case of PBI based on 5-tert-butyl isophthalic acid. Gas diffusion coefficients were estimated from solubility and permeability coefficient determinations. These, along with dual-mode sorption parameters estimated from sorption isotherms provided an insight towards variations in permeation behavior. The permeability predictions for heavier gases in isophthalic acid based PBI correlated well with physical properties. The occurrence of permeation characteristics (especially P-H2 and P-H2/P-N2) near Robeson's upper bound, high thermal stability and good solvent solubility achieved by these structural modifications depicted the potential of this family of polymers as gas separation membrane materials. (c) 2006 Elsevier B.V. All rights reserved.</p>10aDiffusion10aGas permeation10aPolybenzimidazole10aSorption10athermal stability1 aKumbharkar, Santosh, C.1 aKaradkar, Prasad, B.1 aKharul, Ulhas, K.  uhttps://library.ncl.res.in/content/enhancement-gas-permeation-properties-polybenzimidazoles-systematic-structure-architecture-0