@article { ISI:000232046200030, title = {Benzoylation of polyphenylene oxide: characterization and gas permeability investigations}, journal = {European Polymer Journal}, volume = {41}, number = {10}, year = {2005}, month = {OCT}, pages = {2461-2471}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

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.

}, keywords = {benzoylation, Gas permeability, polyphenylene oxide, selectivity}, issn = {0014-3057}, doi = {10.1016/j.eurpolymj.2005.03.026}, author = {Bhole, Yogesh S. and Kharul, Ulhas K. and Somani, S. P. and Kumbharkar, S. C.} } @article { ISI:000251722700028, title = {Assessing feasibility of polyarylate-clay nanocomposites towards improvement of gas selectivity}, journal = {Journal of Membrane Science}, volume = {306}, number = {1-2}, year = {2007}, month = {DEC}, pages = {277-286}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

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.

}, keywords = {Gas permeation, Nanocomposites, polyarylates, selectivity, solution intercalation}, issn = {0376-7388}, doi = {10.1016/j.memsci.2007.09.001}, author = {Bhole, Yogesh S. and Wanjale, Santosh D. and Kharul, Ulhas K. and Jog, Jyoti Prakash} } @article { ISI:000251631200005, title = {Effect of substituent polarity, bulk, and substitution site toward enhancing gas permeation in dibromohexafluorobisphenol-A based polyarylates}, journal = {Journal of Polymer Science Part B-Polymer Physics}, volume = {45}, number = {23}, year = {2007}, month = {DEC}, pages = {3156-3168}, publisher = {JOHN WILEY \& SONS INC}, type = {Article}, address = {111 RIVER ST, HOBOKEN, NJ 07030 USA}, abstract = {

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{\textquoteright}-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.

}, keywords = {asymmetric substitution, Diffusion, Gas permeation, gas sorption, polyarylates, selectivity, structure-property relations}, issn = {0887-6266}, doi = {10.1002/polb.21314}, author = {Ishole, Yogesh S. and Karadkar, Prasad R. and Kharul, Ulhas K.} } @article { ISI:000255339200058, title = {Synthesis, characterization, and gas permeability of aromatic polyimides containing pendant phenoxy group}, journal = {Journal of Applied Polymer Science}, volume = {108}, number = {6}, year = {2008}, month = {JUN}, pages = {3881-3889}, publisher = {JOHN WILEY \& SONS INC}, type = {Article}, address = {111 RIVER ST, HOBOKEN, NJ 07030 USA}, abstract = {

A diamine containing a pendant phenoxy group, 1-phenoxy-2,4-diaminobenzene, was synthesized and condensed with different aromatic dianhydrides [4,4{\textquoteright}-oxydiphthalic dianhydride, 4,4{\textquoteright}-(hexafluoroisopropylidene)diphthalic anhydride, 3,3{\textquoteright},4,4-benzophenone tetracarboxylic dianhydride, 3,3{\textquoteright},4,4{\textquoteright}-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{\textquoteright}-oxydiphthalic dianhydride and 4,4{\textquoteright}-(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.

}, keywords = {Gas permeation, membranes, polyimides, selectivity, structure-property relations}, issn = {0021-8995}, doi = {10.1002/app.28074}, author = {Kothawade, Sandeep S. and Kulkarni, Mahesh P. and Kharul, Ulhas K. and Patil, Anandrao S. and Vernekar, Subhash P.} }