02009nas a2200205   4500008004100000022001400041245015300055210006900208260007100277300001400348490000800362520117500370100002001545700003001565700002501595700001601620700002301636700001501659856012901674       2012                        eng d  a1520-610600aMolecular dynamics simulation of phosphoric acid doped monomer of polybenzimidazole: a potential component polymer electrolyte membrane of fuel cell0 aMolecular dynamics simulation of phosphoric acid doped monomer o  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUN  a7357-73660 v1163 a<p>Phosphoric acid doped polybenzimidazole is promising electrolyte membranes for high temperature (100 degrees C and above) fuel cells. Proton conduction is governed by the amount of phosphoric acid content in the polymer membrane. In this present work, we perform molecular dynamics simulations on phosphoric acid doped 2-phenyl-1H,1'H-5,5'-bibenzo[d]imidazole (monomer unit of polybenzimidazole) to characterize the structural and dynamical properties at varying phosphoric acid content and temperature. From the structural analysis, we have predicted the arrangement of the phosphoric acids, formation of H-bonds in the system, and the contribution of different atoms toward H-bonding. We have also examined the stacking of 2-phenyl-1H,1'H-5,5'-bibenzo[d]imidazole molecules and how their arrangement changes with the increasing amount of PA in the system with the help of cluster analysis. From the molecular dynamics simulation conducted at different temperatures and phosphoric acid doping level, we have predicted the diffusion of phosphoric acid and monomer. As a dynamic quantity, we have also calculated ring flipping of the imidazole ring of the monomer.</p>1 aPahari, Swagata1 aChoudhury, Chandan, Kumar1 aPandey, Prithvi, Raj1 aMore, Minal1 aVenkatnathan, Arun1 aRoy, Sudip  uhttps://library.ncl.res.in/content/molecular-dynamics-simulation-phosphoric-acid-doped-monomer-polybenzimidazole-potential-001870nas a2200229   4500008004100000022001400041245012800055210006900183260005700252300001200309490000700321520101000328653002601338653001801364653002301382653003401405100001601439700002001455700001501475700002301490856012701513       2013                        eng d  a1610-294000aCharacterization of the structures and dynamics of phosphoric acid doped benzimidazole mixtures: a molecular dynamics study0 aCharacterization of the structures and dynamics of phosphoric ac  a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcJAN  a109-1180 v193 a<p>Benzimidazole-based polymer membranes like poly(2,5-benzimidazole) (ABPBI) doped with phosphoric acid (PA) are electrolytes that exhibit high proton conductivity in fuel cells at elevated temperatures. The benzimidazole (BI) moiety is an important constituent of these membranes, so the present work was performed in order to achieve a molecular understanding of the BI-PA interactions in the presence of varying levels of the PA dopant, using classical molecular dynamics (MD) simulations. The various hydrogen-bonding interactions, as characterized based on structural properties and hydrogen-bond lifetime calculations, show that both BI and PA molecules exhibit dual proton-acceptor/donor functionality. An examination of diffusion coefficients showed that the diffusion of BI decreases with increasing PA uptake, whereas the diffusion of PA slightly increases. The hydrogen-bond lifetime calculations pointed to the existence of competitive hydrogen bonding between various sites in BI and PA.</p>10aDiffusion coefficient10aHydrogen bond10amolecular dynamics10aRadial distribution functions1 aMore, Minal1 aPahari, Swagata1 aRoy, Sudip1 aVenkatnathan, Arun  uhttps://library.ncl.res.in/content/characterization-structures-and-dynamics-phosphoric-acid-doped-benzimidazole-mixtures-001939nas a2200157   4500008004100000022001400041245011500055210006900170260012500239300001100364490000800375520123400383100002001617700001501637856012901652       2013                        eng d  a0021-960600aEvidence and characterization of dynamic heterogeneity in binary mixtures of phosphoric acid and benzimidazole0 aEvidence and characterization of dynamic heterogeneity in binary  aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScOCT  a1547010 v1393 a<p>We report here anomalous diffusions of components in mixtures of monomer of polybenzimidazole, i.e., 2-phenyl-1H, 1'H-5,5'-bibenzo[d] imidazole (BI) and phosphoric acid (PA) from molecular dynamics simulations. We have observed initial drop and further increase in self-diffusion constant for both monomer molecule (BI) and PA with gradual increase in PA concentration. The origin of such anomalous diffusion is identified in this work, which happens to be the presence of dynamic heterogeneity in each component of the binary mixture. We characterized microscopic picture of dynamical heterogeneity by finding correlation between dynamical heterogeneity and structural arrangement among the components of the binary system. Different types of H-bonding arrangements in the BI-PA systems at different concentration of PA are observed. The stability of the H-bonded network consisting of different types of H-bonds between BI and PA in the system has been studied by calculating the lifetime of various H-bonds. The results indicate that there are fast and slow moving PA molecules in the mixtures because of coexistence of different types of hydrogen bonds among the components of the mixture. (C) 2013 AIP Publishing LLC.</p>1 aPahari, Swagata1 aRoy, Sudip  uhttps://library.ncl.res.in/content/evidence-and-characterization-dynamic-heterogeneity-binary-mixtures-phosphoric-acid-and-001718nas a2200157   4500008004100000022001400041245012900055210006900184260011000253300001600363490000700379520101300386100002001399700001501419856012601434       2015                        eng d  a1463-907600aProton transport mechanism of imidazole, triazole and phosphoric acid mixtures from ab initio molecular dynamics simulations0 aProton transport mechanism of imidazole triazole and phosphoric   aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcOCT  a30551-305590 v173 a<p>We performed first principles molecular dynamics simulations to elucidate the mechanism and role of 1,2,3-triazole in proton transport while it is mixed with phosphoric acid (PA) and a phosphoric acid imidazole mixture. PA doped imidazole based polymer acts as an efficient polyelectrolyte membrane for fuel cells. The conductivity of this membrane increases when triazole is added to the system. For the first time we performed ab initio molecular dynamics simulations of complex mixtures of PA, imidazole and triazole. We have quantitatively estimated the structural diffusion and vehicular motion of protons. We found that upon the addition of triazole in PA and the PA imidazole mixture, the structural diffusion of protons increases significantly. The mechanism of proton transport is different when triazole is added to the mixture. We have also identified two different paths for structural diffusion (constructive and non-constructive) that contribute to long and short range proton transport.</p>1 aPahari, Swagata1 aRoy, Sudip  uhttps://library.ncl.res.in/content/proton-transport-mechanism-imidazole-triazole-and-phosphoric-acid-mixtures-ab-initio-002168nas a2200157   4500008004100000022001400041245014700055210006900202260011000271300001400381490000600395520144800401100002001849700001501869856012601884       2016                        eng d  a2046-206900aStructural and conformational properties of polybenzimidazoles in melt and phosphoric acid solution: a polyelectrolyte membrane for fuel cells0 aStructural and conformational properties of polybenzimidazoles i  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcDEC  a8211-82210 v63 a<p>Poly[2,2'-(p-phenylene)-5,5'-bibenzimidazole (PBI) and poly(2,5-benzimidazole) (ABPBI) doped with phosphoric acid (PA) are considered as potential polymer electrolyte membranes for high temperature fuel cells. Conformational and structural properties of polymer chains in the presence of PA govern the function of the membrane. Therefore, in this work, a single chain conformational analysis of ABPBI and PBI in melt as well as in PA was performed using classical molecular dynamics simulations. End-to-end distance and the radius of gyration reveal significant changes in the conformations of PBI and ABPBI in PA. The structural changes are analyzed locally segment-wise as well as globally in these polymers. The shape and nature of the curvature along the chain is found to be significantly different for ABPBI and PBI. The role of the solvent (PA) on the chain backbone structure is explored for PA doped ABPBI and PBI chains. The PA arrangement along the backbone confirms that benzimidazole density in the case of both of the polymers determines the PA absorbing capacity. The H-bonding interactions between various atoms of the polymer backbone and the atoms of the PA molecules are evaluated along the polymer chain which relates to the arrangement of PA along the backbone. The reasons for the varying number of H-bonds along ABPBI and PBI which in turn has a significant effect on the stiffness of the chains are investigated.</p>1 aPahari, Swagata1 aRoy, Sudip  uhttps://library.ncl.res.in/content/structural-and-conformational-properties-polybenzimidazoles-melt-and-phosphoric-acid-102459nas a2200241   4500008004100000022001400041245013700055210006900192260000800261300001400269490000700283520159400290100002701884700002401911700002001935700002201955700002501977700002402002700002802026700001502054700002102069856012702090       2018                        eng d  a1744-683X00aMechanism of the formation of microphase separated water clusters in a water-mediated physical network of perfluoropolyether tetraol0 aMechanism of the formation of microphase separated water cluster  cMAR  a2339-23450 v143 a<p>Perfluoropolyether tetraol (PFPE tetraol) possesses a hydrophobic perfluoropolyether chain in the backbone and two hydroxyl groups at each chain terminal, which facilitates the formation of hydrogen bonds with water molecules resulting in the formation an extended physical network. About 3 wt% water was required for the formation of the microphase separated physical network of PFPE tetraol. The mechanism responsible for the microphase separation of water clusters in the physical network was studied using a combination of techniques such as NMR spectroscopy, molecular dynamics (MD) simulations and DSC. MD simulation studies provided evidence for the formation of clusters in the PFPE tetraol physical network and the size of these clusters increased gradually with an increase in the extent of hydration. Both MD simulations and NMR spectroscopy studies revealed that these clusters position themselves away from the hydrophobic backbone or vice versa. The presence of intra-and inter-chain aggregation possibility among hydrophilic groups was evident. DSC results demonstrated the presence of tightly and loosely bound water molecules to the terminal hydroxyl groups of PFPE tetraol through hydrogen bonding. The data from all the three techniques established the formation of a physical network driven by hydrogen bonding between the hydrophilic end groups of PFPE tetraol and water molecules. The flexible nature of the PFPE tetraol backbone and its low solubility parameter favour clustering of water molecules at the terminal groups and result in the formation of a gel.</p>1 aDeshpande, Ashwini, A.1 aTorris, Arun, A. T.1 aPahari, Swagata1 aMenon, Shamal, K.1 aBadiger, Manohar, V.1 aRajamohanan, P., R.1 aWadgaonkar, Prakash, P.1 aRoy, Sudip1 aTonelli, Claudio  uhttps://library.ncl.res.in/content/mechanism-formation-microphase-separated-water-clusters-water-mediated-physical-network