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-001918nas a2200205   4500008004100000022001400041245009000055210006900145260010600214300001400320490000700334520112000341653001901461653002101480653001901501653002201520100002801542700002201570856012001592       2009                        eng d  a0014-305700aN-substitution of polybenzimidazoles: synthesis and evaluation of physical properties0 aNsubstitution of polybenzimidazoles synthesis and evaluation of   aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcDEC  a3363-33710 v453 a<p>Series of N-substituted polybenzimidazoles (PBI) were synthesized using selective alkyl groups with varying bulk and flexibility, viz., methyl, n-butyl, methylene trimethylsilane and 4-tert-butylbenzyl. PBl-I based on 3,3'-diaminobenzidine (DAB) and isophthalic acid and PBI-Bul based on DAB and 5-tert-butyl isophthalic acid were chosen for N-substitution. Structural characterizations of substituted polymers by FT-IR and (1)H NMR revealed elimination of hydrogen bonding. Evaluation of their physical properties revealed that N-substitution rendered better solvent solubility in common organic solvents, more open polymer matrix, but reduced thermal properties in comparison to their respective parent PBI. 4-tert-butylbenzyl, methylene trimethylsilane or n-butyl group substituted polymers were soluble even in chlorinated solvents (CHCl(3) and TCE). Substantial variations in gas permeability of inert gases, He and Ar and attractive P(He)/P(Ar) selectivity, especially after methyl group substitution depicted potential of these materials for gas separation. (C) 2009 Elsevier Ltd. All rights reserved.</p>10aGas permeation10ahydrogen bonding10aN-Substitution10aPolybenzimidazole1 aKumbharkar, Santosh, C.1 aKharul, Ulhas, K.  uhttps://library.ncl.res.in/content/n-substitution-polybenzimidazoles-synthesis-and-evaluation-physical-properties-002150nas a2200217   4500008004100000022001400041245011100055210006900166260007300235300001200308490000800320520134100328653001401669653001901683653001901702653002201721653001301743100002801756700002201784856012601806       2010                        eng d  a0376-738800aInvestigation of gas permeation properties of systematically modified polybenzimidazoles by N-substitution0 aInvestigation of gas permeation properties of systematically mod  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJUL  a134-1420 v3573 a<p>Gas permeation behavior of a series of thermally stable N-substituted polybenzimidazoles by systematically varying bulk and flexibility of the substituent was investigated. Two different PBIs having variation in their acid moiety, viz., PBI-I (based on isophthalic acid) and PBI-BuI (based on 5-tert-butyl isophthalic acid) were selected for N-substitution by alkyl groups possessing different bulk and flexibility. These substituent groups were methyl, n-butyl, methylene trimethylsilane and 4-tert-butylbenzyl. Pure gas sorption and permeability using H(2), N(2), O(2), CH(4) and CO(2) were investigated and correlated with physical properties of formed polymers. Estimation of dual-mode sorption parameters, coefficients of sorption, permeability and diffusion for different gases provided an insight towards effects of nature of a substituent group and parent PBI on governing gas sorption and permeation properties. By changing the substituent group, diffusivity coefficients was found to vary to a larger extent than the solubility coefficient. This significantly enhanced gas permeability for different gases by 1.2-129 times than that of parent PBIs. The permselectivity P(O2)/P(N2) was increased (up to 237%), while for other gas pairs, it was decreased to a different extent. (C) 2010 Elsevier B.V. All rights reserved.</p>10aDiffusion10aGas permeation10aN-Substitution10aPolybenzimidazole10aSorption1 aKumbharkar, Santosh, C.1 aKharul, Ulhas, K.  uhttps://library.ncl.res.in/content/investigation-gas-permeation-properties-systematically-modified-polybenzimidazoles-n-002064nas a2200217   4500008004100000022001400041245012200055210006900177260007300246300001200319490000800331520120300339653001901542653003301561653002201594653002701616100002401643700002801667700002201695856012901717       2014                        eng d  a0376-738800aInvestigation of gas permeation properties of film forming polymeric ionic liquids (PILs) based on polybenzimidazoles0 aInvestigation of gas permeation properties of film forming polym  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcNOV  a494-5030 v4703 a<p>Polymeric ionic liquids (PILs) are emerging as new generation membrane materials for CO2 separation. Gas permeation properties of a recently developed PIL family based on three structurally different polybenzimidazoles (PBIs) possessing excellent film forming characteristics are reported. Effects of cationic backbone and anions on gas permeation properties of PILs using pure gases (He, H-2, N-2, CH4, and CO2) were examined at 20 atm upstream pressure and correlated with their physical properties. In comparison to the parent PBIs, PILs exhibited generally higher CO2 permeability, without largely affecting CO2 based selectivity. Some of these PILs exhibiting high PCO2/PCH4, selectivity and P-H2/P-CO2, approaching similar to 1 indicated dominance of CO2 sorption over diffusion. The CO2 sorption specificity of these PILs was distinctly observed based on their improved S-CO2/S-N2, S-CO2/S-CH4 and S-CO2/S-H2 selectivity than their parent PBIs. A large variation in permeation properties of PILs based on a common polycation but different anions indicated that anions play a crucial role on governing gas permeation properties of these PILs. (C) 2014 Elsevier B.V. All rights reserved</p>10aGas permeation10aMembranes for CO2 separation10aPolybenzimidazole10aPolymeric ionic liquid1 aBhavsar, Rupesh, S.1 aKumbharkar, Santosh, C.1 aKharul, Ulhas, K.  uhttps://library.ncl.res.in/content/investigation-gas-permeation-properties-film-forming-polymeric-ionic-liquids-pils-based-0