02011nas a2200229 4500008004100000022001400041245009400055210006900149260010600218300001400324490000700338520114600345653001701491653002101508653002401529653001601553100002201569700002201591700001901613700002301632856012601655 2005 eng d a0014-305700aBenzoylation of polyphenylene oxide: characterization and gas permeability investigations0 aBenzoylation of polyphenylene oxide characterization and gas per aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcOCT a2461-24710 v413 a

Benzoylation of polyphenylene oxide (PPO) was carried out with aromatic acid chlorides bearing specific groups at para-position (H methyl, Br, Cl and nitro), which differ in their polarity and bulk. The reaction conditions were optimized individually to get the high degree of substitution. These materials were characterized for thermal as well as other physical properties that are known to affect the gas permeation. In a series investigated, the nitrobenzoyl substitution on PPO resulted in the highest increase in glass transition temperature and the lowest thermal stability. An estimation of the packing density parameters-fractional free volume by density measurement and the d-spacing by X-ray diffraction analysis showed an increase in the packing density. The gas permeability was found to decrease in all the cases of benzoylation. The helium and oxygen based selectivities were increased, while CO2 based selectivities were decreased. The unusual trend observed in the gas permeation properties is explained on the basis of nature of substituent and the degree of substitution. (c) 2005 Elsevier Ltd. All rights reserved.

10abenzoylation10aGas permeability10apolyphenylene oxide10aselectivity1 aBhole, Yogesh, S.1 aKharul, Ulhas, K.1 aSomani, S., P.1 aKumbharkar, S., C. uhttp://library.ncl.res.in/content/benzoylation-polyphenylene-oxide-characterization-and-gas-permeability-investigations-002269nas a2200241 4500008004100000022001400041245010000055210006900155260007300224300001200297490000800309520138900317653001901706653001901725653001701744653001601761653002701777100002201804700002501826700002201851700002401873856013001897 2007 eng d a0376-738800aAssessing feasibility of polyarylate-clay nanocomposites towards improvement of gas selectivity0 aAssessing feasibility of polyarylateclay nanocomposites towards  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcDEC a277-2860 v3063 a

Polymer-clay nanocomposites are well known to reduce the penetrant permeability by following tortuous path. Effects of such reduction in gas permeability on variation in selectivity of nanocomposites prepared using a high permeability polymer were examined. The polyarylate: poly (tetramethyl bisphenolA-iso/terephthalate) that exhibits high permeability and moderate selectivity was chosen for making nanocomposites with two organically modified clays (Cloisite 6A and 10A) by solution intercalation method. The nanocomposite formation for various clay loadings (3, 5 and 7% w/w) in polyarylate was ascertained by change in physical properties (X-ray diffraction, DMA, TEM). Behavior of solution viscosity and nanocomposite density indicated existence of polymer-clay layer interactions. As anticipated, though the gas permeability of pure gases, viz., He, N-2, CH4 and CO2 exhibited decrease, it was not monotonous. This decrease was more for larger gases (N-2, CH4 and CO2) in comparison to the decrease for smaller gas (He) permeability. This led to a decrease in CO2/N-2 and CO2/CH4 selectivities and increase in He/CO2 selectivity; while He/CH4 selectivity was increased substantially at 7% clay loading. This variation indicated feasibility of nanocomposites formation as a tool for improving selectivity of certain gas pairs. (c) 2007 Elsevier B.V. All rights reserved.

10aGas permeation10aNanocomposites10apolyarylates10aselectivity10asolution intercalation1 aBhole, Yogesh, S.1 aWanjale, Santosh, D.1 aKharul, Ulhas, K.1 aJog, Jyoti, Prakash uhttp://library.ncl.res.in/content/assessing-feasibility-polyarylate-clay-nanocomposites-towards-improvement-gas-selectivity-002182nas a2200253 4500008004100000022001400041245014700055210006900202260006800271300001400339490000700353520122700360653002801587653001401615653001901629653001701648653001701665653001601682653003301698100002301731700002501754700002201779856012701801 2007 eng d a0887-626600aEffect of substituent polarity, bulk, and substitution site toward enhancing gas permeation in dibromohexafluorobisphenol-A based polyarylates0 aEffect of substituent polarity bulk and substitution site toward a111 RIVER ST, HOBOKEN, NJ 07030 USAbJOHN WILEY & SONS INCcDEC a3156-31680 v453 a

The gas permeation properties of polyarylates were tuned by varying nature and site of substituents present on both of its monomers, viz., bisphenol and dicarboxylic acid. The phenyl rings of hexafluorobisphenol-A were substituted in asymmetric manner by polar bromine to obtain dibromohexafluorobisphenol-A. This bisphenol was polymerized with equimolar mixture of iso- and terephthalic acid (base case), bromo- and nitroterephthalic acid (polar group substituted acids), 4,4'-hexafluoroisopropylidene bis(benzoic acid), and t-butyl isophthalic acid (bulky group containing acids). Physical properties and gas permeation properties of these polyarylates were investigated to assess combined effects of asymmetric nature of bisphenol substitution, polar nature of substituent bromine, hexafluoroisopropylidene group present at the bridge position of bisphenol, and substituent present on the acid moiety. The combination of these substituent types led these polyarylates to lie near Robeson upper bound. The gas sorption analysis and estimation of diffusivity in these polyarylates shed a light on observed variations in gas permeation properties by attempted structural variations. (c) 2007 Wiley Periodicals, Inc.

10aasymmetric substitution10aDiffusion10aGas permeation10agas sorption10apolyarylates10aselectivity10astructure-property relations1 aIshole, Yogesh, S.1 aKaradkar, Prasad, R.1 aKharul, Ulhas, K. uhttp://library.ncl.res.in/content/effect-substituent-polarity-bulk-and-substitution-site-toward-enhancing-gas-permeation-002231nas a2200253 4500008004100000022001400041245011000055210006900165260006800234300001400302490000800316520130500324653001901629653001401648653001501662653001601677653003301693100002701726700002501753700002201778700002401800700002601824856012701850 2008 eng d a0021-899500aSynthesis, characterization, and gas permeability of aromatic polyimides containing pendant phenoxy group0 aSynthesis characterization and gas permeability of aromatic poly a111 RIVER ST, HOBOKEN, NJ 07030 USAbJOHN WILEY & SONS INCcJUN a3881-38890 v1083 a

A diamine containing a pendant phenoxy group, 1-phenoxy-2,4-diaminobenzene, was synthesized and condensed with different aromatic dianhydrides [4,4'-oxydiphthalic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracorboxylic dianhydride, and pyromellitic dianhydride] by one-step synthesis at a high temperature in m-cresol to obtain polyimides in high yields. Most of the polyimides exhibited good solvent solubility and could be readily dissolved in chloroform, sym-tetrachloroethane, N,N-dimethylformamide, NN-dimethylacetamide, and nitrobenzene. Their inherent viscosities were in the range of 0.33-1.16 dL/g. Wide-angle X-ray spectra revealed that these polymers were amorphous in nature. All these polyimides were thermally stable, having initial decomposition temperatures above 500 degrees C and glass-transition temperatures in the range of 248-281 degrees C. The gas permeability of 4,4'-oxydiphthalic dianhydride and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride based polyimides was investigated with pure gases: He, H-2, O-2, Ar, N-2, CH4, and CO2. A polyimide containing a -C(CF3)(2)- linkage showed a good combination of permeability and selectivity. (C) 2008 Wiley Periodicals, Inc.

10aGas permeation10amembranes10apolyimides10aselectivity10astructure-property relations1 aKothawade, Sandeep, S.1 aKulkarni, Mahesh, P.1 aKharul, Ulhas, K.1 aPatil, Anandrao, S.1 aVernekar, Subhash, P. uhttp://library.ncl.res.in/content/synthesis-characterization-and-gas-permeability-aromatic-polyimides-containing-pendant-0