02034nas a2200157   4500008004100000022001400041245013800055210006900193260011000262300001400372490000600386520130800392100003001700700001501730856013101745       2013                        eng d  a1744-683X00aStructural and dynamical properties of polyethylenimine in explicit water at different protonation states: a molecular dynamics study0 aStructural and dynamical properties of polyethylenimine in expli  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcJAN  a2269-22810 v93 a<p>PEI is a pH sensitive polymer which acts as a proton sponge in acidic conditions. Despite many experimental and theoretical efforts, a fundamental understanding of the structure and dynamics of linear PEI chains on the atomistic level at different protonation states in dilute solutions remains a topic of discussion. This report analyses the structural properties of PEI at different protonation states, which are representative of different pH, using all atomistic molecular dynamic simulations. The structural properties revealed that the polymer at high pH (basic medium) is highly coiled, while at low pH (strong acidic conditions) the chains are elongated. We studied the dynamics and ordering of water molecules that are part of the solvation shells of the PEI chains at different protonation states. We observe that the water molecules are ordered along the polymer backbone for a completely protonated PEI chain (i.e. in the case of acidic pH) and hop to the neighbouring solvation shell. The residence time and the self-diffusion of water molecules in the solvation shells and their activation barriers were also calculated and analysed further. We concluded the study by correlating the solvation shell water dynamics and the structure of the PEI chain at different protonation states.</p>1 aChoudhury, Chandan, Kumar1 aRoy, Sudip  uhttps://library.ncl.res.in/content/structural-and-dynamical-properties-polyethylenimine-explicit-water-different-protonation-002001nas a2200157   4500008004100000245013200041210006900173260000800242300001200250490000700262520138100269100003001650700001901680700001501699856012901714       2016                        eng d00aScalability of coarse-grained potentials generated from iterative boltzmann inversion forpolymers: case study on polycarbonates0 aScalability of coarsegrained potentials generated from iterative  cMAY  a274-2860 v253 aUsing systematic coarse-grained (CG) techniques such as iterative Boltzmann inversion (IBI) is an efficient means to simulate high molecular weight polymer melts within reasonable computational time. One drawback of such an approach is however the need to carry out extensive atomistic simulations in order to extrapolate the necessary distributions to derive the inter and intrabead force field parameters. Here it is shown that it is possible to use atomistic simulations of relative short oligomers to develop the CG model for high molecular weight polymers. In particular for the specific case of polycarbonates, it is found that the structural properties (end-to-end distance, radius of gyration and their distributions) are similar irrespective of whether the CG potentials are derived from 5-mer or 10-mer melt systems. Dynamical properties of the CG systems are smoother and faster than the atomistic ones. Scaling factor, derived by overlapping the CG mean square displacement curves (obtained from different CG IBI potentials) over the atomistic ones, also scales the autocorrelation functions. A prediction of the dynamical scaling factor in the case of the unavailability of atomistic simulations is also discussed. The dynamical properties of the CG melts are modeled reasonably well by all the CG potentials derived from atomistic simulations of short oligomers.1 aChoudhury, Chandan, Kumar1 aCarbone, Paola1 aRoy, Sudip  uhttps://library.ncl.res.in/content/scalability-coarse-grained-potentials-generated-iterative-boltzmann-inversion-forpolymers02011nas a2200289   4500008004100000022001400041245008000055210006900135260007100204300001400275490000800289520102800297100001901325700002401344700002301368700002201391700003001413700002101443700002001464700002501484700002101509700001901530700001501549700002201564700002001586856011501606       2017                        eng d  a0002-786300aSelf-exfoliated guanidinium-based ionic covalent organic nanosheets (iCONs)0 aSelfexfoliated guanidiniumbased ionic covalent organic nanosheet  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAR  a2823-28280 v1383 a<p>Covalent organic nanosheets (CONs) have emerged as functional two-dimensional materials for versatile applications. Although pi-pi stacking between layers, hydrolytic instability, possible restacking prevents their exfoliation on to few thin layered CONs from crystalline porous polymers. We anticipated rational designing of a structure by intrinsic ionic linker could be the solution to produce self-exfoliated CONs without external stimuli. In an attempt to address this issue, we have synthesized three self-exfoliated guanidinium halide based ionic covalent organic nanosheets (iCONs) with antimicrobial property. Self-exfoliation phenomenon has been supported by molecular dynamics (MD) simulation as well. Intrinsic ionic guanidinium unit plays the pivotal role for both self-exfoliation and antibacterial property against both Gram-positive and Gram-negative bacteria. Using such iCONs, we have devised a Mixed matrix membrane which could be useful for antimicrobial coatings with plausible medical benefits.</p>1 aMitra, Shouvik1 aKandambeth, Sharath1 aBiswal, Bishnu, P.1 aKhayum, Abdul, M.1 aChoudhury, Chandan, Kumar1 aMehta, Mihir, R.1 aKaur, Gagandeep1 aBanerjee, Subhrashis1 aPrabhune, Asmita1 aVerma, Sandeep1 aRoy, Sudip1 aKharul, Ulhas, K.1 aBanerjee, Rahul  uhttps://library.ncl.res.in/content/self-exfoliated-guanidinium-based-ionic-covalent-organic-nanosheets-icons-0