@article { ISI:000278905100015, title = {Investigation of gas permeation properties of systematically modified polybenzimidazoles by N-substitution}, journal = {Journal of Membrane Science}, volume = {357}, number = {1-2}, year = {2010}, month = {JUL}, pages = {134-142}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

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.

}, keywords = {Diffusion, Gas permeation, N-Substitution, Polybenzimidazole, Sorption}, issn = {0376-7388}, doi = {10.1016/j.memsci.2010.04.014}, author = {Kumbharkar, Santosh C. and Kharul, Ulhas K.} } @article { ISI:000290167200026, title = {Improved performance of phosphonated carbon nanotube-polybenzimidazole composite membranes in proton exchange membrane fuel cells}, journal = {Journal of Materials Chemistry}, volume = {21}, number = {20}, year = {2011}, month = {APR}, pages = {7223-7231}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Development of thermally stable polymer electrolyte membranes with higher proton conductivity as well as mechanical stability is a key challenge in commercializing PEM fuel cells operating above 100 degrees C. Polybenzimidazole membranes are one of the promising candidates in this category although with limited mechanical stability and moderate proton conductivity. Here the incorporation of functionalized MWCNT is shown to increase both these key parameters of the polybenzimidazole membranes. Further, formation of a domain like structure after the incorporation of phosphonated MWCNTs (P-MWCNTs) in phosphoric acid doped polybenzimidazole membranes is demonstrated. The enhanced performance has been attributed to the formation of proton conducting networks that formed along the sidewalls of P-MWCNTs with a domain size of 17 nm as estimated from the small angle X-ray scattering measurements. Membrane electrode assembly (MEA) impedance measurements further reveal that the activation energy of oxygen reduction reaction (ORR) reduced for the composite membranes with enhanced proton conductivity. In addition, the mechanical strength measurements reveal a significant improvement in the yield strength and ultimate strength. Also, the mechanical strength of the composite membrane has been increased significantly as indicated by the improvement in the ultimate strength from 65 MPa to 100 MPa for the pristine and composite membranes, respectively. The optimum loading of P-MWCNTs is found to be 1\% as inferred from the polarization measurements carried out using pure hydrogen and oxygen. Thus, this study provides a unique opportunity to tune the properties of polymer electrolytes to prepare application oriented hybrid membranes using CNTs with tailor-made functional groups.

}, issn = {0959-9428}, doi = {10.1039/c0jm04265j}, author = {Kannan, Ramaiyan and Kagalwala, Husain N. and Chaudhari, Harshal D. and Kharul, Ulhas K. and Kurungot, Sreekumar and Pillai, Vijayamohanan K.} } @article { ISI:000321864300019, title = {In situ growth of metal-organic frameworks on a porous ultrafiltration membrane for gas separation}, journal = {Journal of Materials Chemistry A}, volume = {1}, number = {31}, year = {2013}, month = {MAY}, pages = {8828-8835}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

We demonstrate the synthesis of CuBTC and ZIF-8 on a polysulfone based porous asymmetric ultrafiltration (UF) membrane by in situ growth followed by the LBL deposition of crystals without any need for preseeding or surface modification of the membrane. In this way, the top surface of the UF membrane pores is completely covered by MOFs; while the remaining part of the membrane offers a flexible support to the MOFs. The pore apertures of the MOF nanoparticles located at the pore opening of the UF membrane act as channels for the entry of penetrants. The remaining porous sublayer of the membrane carries penetrants on the permeate side without significant resistance. These composite membranes were characterized by PXRD and SEM. The gas permeation study was performed using pure gases of industrial significance (H-2, C3H6 and CO2). The performance of CuBTC@PSF showed enhanced selectivity, of 7.2 and 5.7 for H-2/CO2 and H-2/C3H6 respectively, to that of the pristine PSF membrane.

}, issn = {2050-7488}, doi = {10.1039/c3ta10438a}, author = {Nagaraju, Divya and Bhagat, Deepti G. and Banerjee, Rahul and Kharul, Ulhas K.} } @article { ISI:000341141800050, title = {Investigation of gas permeation properties of film forming polymeric ionic liquids (PILs) based on polybenzimidazoles}, journal = {Journal of Membrane Science}, volume = {470}, year = {2014}, month = {NOV}, pages = {494-503}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

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

}, keywords = {Gas permeation, Membranes for CO2 separation, Polybenzimidazole, Polymeric ionic liquid}, issn = {0376-7388}, doi = {10.1016/j.memsci.2014.07.076}, author = {Bhavsar, Rupesh S. and Kumbharkar, Santosh C. and Kharul, Ulhas K.} } @article { ISI:000375647900005, title = {Incorporation of rigid polyaromatic groups in polybenzimidazole-based polymeric ionic liquids: assertive effects on gas permeation properties}, journal = {Polymer}, volume = {93}, year = {2016}, month = {JUN}, pages = {30-36}, publisher = {ELSEVIER SCI LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

Polymeric ionic liquids (PILs) have emerged as promising membrane materials for CO2 separation. The present work is aimed at investigating the effects of incorporation of rigid polyaromatic hydrocarbons, viz., pyrene and anthracene, in polybenzimidazole-based PILs. The effects of substituent and anion variation on the gas permeation properties of PILs using pure gases were examined at 20 atm upstream pressure. The results were correlated with physical properties of PILs. The pyrene substituted PIL exhibited similar to 10 fold increase in CO2 permeability as compared to its precursor polymer PBI-BuI. The combination of a CO2 specific anion and bulky group substitution offered higher CO2 permeability as well as appreciable permselectivity than their structural analogue that was devoid of IL functionality. The permeation properties of present PILs were superior to those of conventional glassy polymers such as polysulfone, matrimid and polycarbonate which are widely studied for their gas permeation properties. (C) 2016 Elsevier Ltd. All rights reserved.

}, keywords = {Gas permeation, membranes, Polymeric ionic liquids}, issn = {0032-3861}, doi = {10.1016/j.polymer.2016.03.093}, author = {Shaligram, Sayali V. and Rewar, Anita S. and Wadgaonkar, Prakash P. and Kharul, Ulhas K.} } @article {44164, title = {Intrinsically microporous polyimides containing spirobisindane and phenazine units: synthesis, characterization and gas permeation properties}, journal = {Journal of Polymer Science Part A - Polymer Chemistry}, volume = {56}, year = {2018}, month = {APR }, pages = {766-775}, abstract = {A new diamine containing spirobisindane and phenazine units, namely, 3,3,3,3-tetramethyl-2,2,3,3-tetrahydro-1,1-spirobi[cyclopenta[b]phen azine]-7,7-diamine (TTSBIDA) was synthesized starting from commercially available 5,5,6,6-tetrahydroxy-3,3,3,3-tetramethyl-1,1-spirobisindane (TTSBI). TTSBI was oxidized to 3,3,3,3-tetramethyl-2,2,3,3-tetrahydro-1,1-spirobi[indene]-5,5,6,6-tet raone (TTSBIQ) which was subsequently condensed with 4-nitro-1,2-phenylenediamine to obtain 3,3,3,3-tetramethyl-7,7-dinitro-2,2,3,3-tetrahydro-1,1-spirobi[cyclope nta[b]phenazine] (TTSBIDN). TTSBIDN was converted into TTSBIDA by reduction of the nitro groups using hydrazine hydrate in the presence of Pd/C as the catalyst. A series of new polyimides of intrinsic microporosity (PIM-PIs) were synthesized by polycondensation of TTSBIDA with commercially available aromatic dianhydrides. PIM-PIs exhibited amorphous nature, high thermal stability (T-10\>480 degrees C) and intrinsic microporosity (BET surface area=59-289 m(2)/g). The gas permeation characteristics of films of selected PIM-PIs were evaluated and they exhibited appreciable gas permeability as well as high selectivity. The CO2 and O-2 permeability of PIM-PIs were in the range 185.4-39.2 and 30.6-6.2 Barrer, respectively. Notably, polyimide derived from TTSBIDA and 4,4-(hexafluoroisopropylidene)diphthalic anhydride (PIM-PI-6FDA) exhibited high CO2 and O-2 permeability of 185.4 and 30.6 Barrer with CO2/CH4 and O-2/N-2 selectivity of 43.1 and 5.1, respectively. The data of PIM-PI-6FDA for CO2/CH4 and O-2/N-2 gas pairs were located near Robeson upper bound. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 766-775}, keywords = {Gas permeability, intrinsic microporosity, polyimides, spirobisindane}, issn = {0887-624X}, doi = {10.1002/pola.28950}, author = {Shrimant, Bharat and Dangat, Yuvraj and Kharul, Ulhas K. and Wadgaonkar, Prakash P.} }