01918nas 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-002284nas a2200229   4500008004100000022001400041245008300055210006900138260007300207300001200280490000800292520149100300653002101791653001401812653001901826653001901845653001101864653001301875100002801888700002201916856011601938       2010                        eng d  a0376-738800aNew N-substituted ABPBI: synthesis and evaluation of gas permeation properties0 aNew Nsubstituted ABPBI synthesis and evaluation of gas permeatio  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcSEP  a418-4250 v3603 a<p>Aromatic poly(2,5-benzimidazole), ABPBI was post-modified for the first time to produce organosoluble N-substituted ABPBI. This modification was carried out by N-substitution of ABPBI with bulky alkyl groups, viz., 4-tert-butylbenzyl and methylene trimethylsilyl in an attempt to utilize high rigidity of ABPBI towards gas permeation. These substituted polymers exhibited solubility in common organic solvents, enhancing their processability than ABPBI, which is soluble only in acidic solvents. Considerable decrease in chain packing density led to increase in gas sorption as that of unsubstituted ABPBI. The permeability of pure gases of commercial significance (He, H(2), N(2), O(2), CH(4) and CO(2)) were high, coupled with attractive selectivities. In comparison to conventional PBI, methylene trimethylsilyl substituted ABPBI led to considerably high (33 folds) CO(2) permeability with almost similar selectivity (P(CO2)/P(N2) approximate to 33). Feasibility of these N-substituted ABPBIs to be converted in to required membrane form along with its considerably higher permeation properties depicted the potential of this polymer to be used as gas separation material. Gas diffusion coefficients were estimated from solubility and permeability coefficient. These, along with dual-mode sorption parameters estimated from sorption isotherms provided an insight towards variations in permeation behavior caused by the substitution. (C) 2010 Elsevier B.V. All rights reserved.</p>10a5-benzimidazole)10aDiffusion10aGas permeation10aN-Substitution10aPoly(210aSorption1 aKumbharkar, Santosh, C.1 aKharul, Ulhas, K.  uhttps://library.ncl.res.in/content/new-n-substituted-abpbi-synthesis-and-evaluation-gas-permeation-properties-0