01972nas a2200193   4500008004100000022001400041245005200055210005200107260008600159300001200245490000800257520134300265653000901608653002801617653001501645653001001660100002701670856008101697       2005                        eng d  a1532-179700aCrystallization of polymers from stressed melts0 aCrystallization of polymers from stressed melts  a325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USAbTAYLOR & FRANCIS INCcOCT  a375-3970 vC453 a<p>In the last decade, there have been several investigations into the route by which a polymer melt that has been subjected to flow transforms into a crystalline state. Crystallization of polymers from flowing or stressed melts is a technologically important problem since most thermoplastics are subjected to intense flow fields during normal processing operations. The renewed interest in this problem is due to the availability of new experimental tools that, coupled with advances in modeling and simulations, are beginning to yield insights into the molecular characteristics that control the crystallization pathways adopted by a stressed polymer melt. Recent evidence conclusively implicates the high molecular weight tail in promoting crystallization on shearing. It appears that the formation of oriented nuclei in polydisperse melts is controlled by chain orientation of a small fraction of high molecular weight chains in a melt. Thus, it is the theological criteria for ``critical'' chain orientation that govern flow-induced acceleration and orientation in polymer crystallization. This review summarizes the literature on the effect of shearing on polymer crystallization, and focuses on recent advances in understanding the role of molecular parameters that couple polymer crystallization to flow and melt orientation.</p>10aflow10apolymer crystallization10aprocessing10ashear1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/crystallization-polymers-stressed-melts-101830nas a2200181   4500008004100000022001400041245010700055210006900162260007100231300001600302490000800318520110300326100002701429700002501456700002501481700001901506856012301525       2005                        eng d  a1520-610600aLayered inorganic-organic clay-like nanocomposites rearrange to form silsesquioxanes on acid treatment0 aLayered inorganicorganic claylike nanocomposites rearrange to fo  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAUG  a16034-160390 v1093 a<p>The formation of talc-like compounds by the condensation of organotrialkoxy silanes with magnesium hydroxide has been recently reported. These represent layered hybrid nanomaterials that have a layer thickness of around 1 nm, have organic moieties covalently linked to the layer surfaces, and are called ``organoclays.'' We show that such compounds are sensitive to acid treatment. When a phenylclay is treated with hydrochloric acid, magnesium leaches out, destroying the layered structure. The extent to which magnesium is leached out is a function of the time of the acid treatment and the concentration of the acid used. Magnesium leaches out rapidly when the concentration of acid used to treat the phenyl-clay is higher, and the extent of structural magnesium that is leached out is also higher for higher acid concentrations. Removal of the magnesium rearranges the structure of the phenyl-clay to form oligomeric phenylsilsesquioxanes. FTIR and NMR suggest that the silsesquioxanes formed by acid treatment of the phenyl-clay comprise a mixture of ladderlike and cagelike structures.</p>1 aKumaraswamy, Guruswamy1 aDeshmukh, Yogesh, S.1 aAgrawal, Vikrant, V.1 aRajmohanan, P.  uhttps://library.ncl.res.in/content/layered-inorganic-organic-clay-nanocomposites-rearrange-form-silsesquioxanes-acid-102131nas a2200217   4500008004100000022001400041245009900055210006900154260009900223300001400322490000700336520130000343653001301643653001501656653002401671100002701695700002001722700002501742700001701767856012901784       2005                        eng d  a0032-386100aPolycondensation in liquid crystalline phases of nonionic surfactants. Kinetics and morphology0 aPolycondensation in liquid crystalline phases of nonionic surfac  aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLANDbELSEVIER SCI LTDcSEP  a7961-79680 v463 a<p>We have investigated acid-catalyzed polycondensation of alkoxysilane monomers in liquid crystalline phases of nonionic CnEm surfactants. The liquid crystalline phase is retained when the monomers polymerize. The high molecular weight molecules formed phase separate from the mesophase and are subsequently organized by it to form micron-sized particles. A variety of particle morphologies are formed by organization of the polymer particles in the mesophase. For condensation of dimethyldimethoxysilane (DMS, with trimethoxysilane, TMS as crosslinker) in hexagonal and lamellar phases, specific reaction conditions, viz. slow condensation kinetics and low crosslink density, give rod-like particles in hexagonal phases and sheet-like structures in lamellar phases. However, when higher acid concentrations are used, the reaction kinetics accelerates and irregular particles form. Irregular particles also form when the fraction of trifunctional crosslinker is increased, and finally complex flower-like structures form for condensation of trimethoxysilane in the hexagonal phase. The particle morphology formed is crucially dependent on the details of the polycondensation rate, crosslinker density and surfactant-monomer/oligomer interactions. (c) 2005 Elsevier Ltd. All rights reserved.</p>10anonionic10asurfactant10atemplated synthesis1 aKumaraswamy, Guruswamy1 aWadekar, M., N.1 aAgrawal, Vikrant, V.1 aPasricha, R.  uhttps://library.ncl.res.in/content/polycondensation-liquid-crystalline-phases-nonionic-surfactants-kinetics-and-morphology-001695nas a2200181   4500008004100000022001400041245005900055210005900114260007100173300001400244490000700258520107100265100002001336700001701356700002001373700002701393856009301420       2005                        eng d  a0897-475600aPolymerization in surfactant liquid crystalline phases0 aPolymerization in surfactant liquid crystalline phases  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAY  a2460-24650 v173 a<p>We report the formation of cross-linked polysiloxane particles having rodlike and sheetlike morphologies by condensation of monomers in organized liquid crystalline mesophases of nonionic surfactants. The characteristic diffraction pattern obtained from the liquid crystalline surfactant assembly is preserved during polymer synthesis. The polymer colloids are rodlike when synthesized in a hexagonal mesophase and are sheetlike when synthesized in a lamellar mesophase. Interestingly, the size of the polymer particles is on the order of micrometers, viz. 3 orders of magnitude larger than the characteristic size of the surfactant mesophase. Thus, the polymers phase separate from the liquid crystalline phase during polymerization, and organize to resemble the mesophase geometry. The polymer particles are organized so as to minimize the elastic distortion of the surfactant mesophase after they phase separate. We speculate that the observed particle morphologies are formed due to the slow kinetics of polycondensation under our experimental conditions.</p>1 aWadekar, M., N.1 aPasricha, R.1 aGaikwad, A., B.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/polymerization-surfactant-liquid-crystalline-phases-002287nas a2200169   4500008004100000022001400041245005400055210005400109260007100163300001400234490000700248520169500255100003101950700002701981700002102008856008802029       2006                        eng d  a0024-929700aCollapse transition in random copolymer solutions0 aCollapse transition in random copolymer solutions  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcDEC  a9621-96290 v393 a<p>We present dynamic Monte Carlo lattice simulations of the coil to globule collapse of single chains of a copolymer comprising monomer units, m and c, wherein there is a net attractive interaction between c-units. As the copolymer is cooled, the solvent quality becomes poorer, and the size of the chain decreases, driven by the net m-m and c-c attractions. The strong c-c attraction increases the overall solvophobicity of the chain relative to a homopolymer and, therefore, copolymers collapse more abruptly and at a higher effective temperature relative to homopolymers. We compare copolymers with homopolymers by rescaling collapse data to the same theta values to account for the effect of overall solvophobicity. This comparison shows that the behavior of copolymers and the corresponding homopolymers is identical as the chain size reduces from high temperatures to the theta value. Beyond theta, copolymers with c-content &lt; similar to 50% collapse more abruptly than either homopolymer, after accounting for the difference in overall solvophobicity. Collapse of copolymers containing higher c-content is dominated entirely by the c-c attractions, and these chains behave qualitatively like homopolymers with a higher effective solvophobicity. Analysis of the chain structure during collapse provides a structural reason for the qualitative change in copolymer collapse at low c-content. When such copolymers are cooled below theta, the c-units rapidly aggregate to form an isotropic, compact core surrounded by an anisotropic solvated shell of m-units. The shell densifies as the copolymer is further cooled, but remains anisotropic for the finite chain sizes investigated.</p>1 aDasmahapatra, Ashok, Kumar1 aKumaraswamy, Guruswamy1 aNanavati, Hemant  uhttps://library.ncl.res.in/content/collapse-transition-random-copolymer-solutions-001694nas a2200169   4500008004100000022001400041245010300055210006900158260012500227300001100352490000800363520094400371100003101315700002101346700002701367856013001394       2007                        eng d  a0021-960600aPathway to copolymer collapse in dilute solution: uniform versus random distribution of comonomers0 aPathway to copolymer collapse in dilute solution uniform versus   aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScDEC  a2349010 v1273 a<p>Monte Carlo simulations show that copolymers with uniformly (or periodically) distributed sticky comonomers collapse ``cooperatively,'' abruptly forming a compact intermediate comprising a monomer shell surrounding a core of the aggregated comonomers. In comparison, random copolymers collapse through a relatively less-compact intermediate comprising a comonomer core surrounded by a fluffy monomer shell that densifies over a wide temperature range. This difference between the collapse pathways for random and uniform copolymers persists to higher chain lengths, where uniform copolymers tend to form multiple comonomer cores. In this paper, we describe the formation of such an intermediate state, and the subsequent collapse, by recognizing that these arise from the expected balance between comonomer aggregation enthalpy and loop formation entropy dictated by the chain microstructure. (c) 2007 American Institute of Physics.</p>1 aDasmahapatra, Ashok, Kumar1 aNanavati, Hemant1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/pathway-copolymer-collapse-dilute-solution-uniform-versus-random-distribution-comonomers-002369nas a2200181   4500008004100000022001400041245010600055210006900161260007100230300001400301490000700315520164200322100002701964700002501991700002502016700001702041856012902058       2008                        eng d  a0888-588500aComposites of polypropylene with layered Mg-silsesquioxanes show an unusual combination of properties0 aComposites of polypropylene with layered Mgsilsesquioxanes show   a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUN  a3891-38990 v473 a<p>We report the synthesis of vinyl modified magnesium silsesqiuoxanes (''vinyl clay''), and the formation of their composites with isotactic polypropylene (iPP) by melt compounding. Vinyl clay is a layered compound with a layer thickness of approximately 1 nm. Vinyl clay does not exfoliate in iPP; rather, it disperses to form a network that exhibits a characteristic low frequency solid-like plateau in the elastic modulus in dynamic melt theological measurements. Strangely, vinyl clay also plasticizes iPP-there is a decrease in the high frequency complex viscosity. The decrease in the complex viscosity is higher at higher frequencies, suggesting the influence of slip at the iPP-vinyl clay interface. The combination of the low frequency elastic plateau and plasticization makes the vinyl clay composite significantly more shear thinning than the matrix iPP. In the solid state, vinyl clay-iPP composites exhibit increased tensile modulus (showing approximate to 50% increase for a 5% loading), but surprisingly, no corresponding decrease in the elongation at break. Thus, while microstructural characterization indicates that only a small fraction, if any, of the vinyl clay is exfoliafed, the enhancement in mechanical properties is similar to that observed for iPP-exfoliated montmonillonite nanocomposites. Our compounding protocol is unable to effectively disperse the clay in the iPP at clay loadings greater than about 7.5%. Therefore, the low frequency plateau in the melt elastic modulus and the solid tensile modulus increase with clay loading until 7.5% but exhibit a nonmonotonic decrease at higher clay loadings.</p>1 aKumaraswamy, Guruswamy1 aDeshmukh, Yogesh, S.1 aAgrawal, Vikrant, V.1 aNisal, Anuya  uhttps://library.ncl.res.in/content/composites-polypropylene-layered-mg-silsesquioxanes-show-unusual-combination-properties-002386nas a2200205   4500008004100000022001400041245011200055210006900167260007100236300001400307490000800321520157900329100002101908700001801929700003201947700002401979700001902003700002702022856013102049       2008                        eng d  a1520-610600aGelation of covalently edge-modified laponites in aqueous media. 1. rheology and nuclear magnetic resonance0 aGelation of covalently edgemodified laponites in aqueous media 1  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAPR  a4536-45440 v1123 a<p>We describe the covalent modification of the edges of laponite with organic groups and the influence of this modification on gelation behavior. We compare three materials: an unmodified laponite, a laponite edge modified with a trimethyl moiety (MLap), and an octyldimethyl moiety (OLap). Gelation is investigated using rheology and NMR T-1 relaxation measurements and nuclear Overhauser enhancement spectroscopy (NOESY). MLap and OLap show qualitatively different gelation. Gelation of MLap is very similar to laponite: MLap gels over the same time scale as laponite and has about the same solid modulus, and the MLap gel is almost as transparent as laponite. In contrast, OLap gels rapidly relative to laponite and forms a weak, turbid gel. We believe that gelation in laponite and MLap results from the formation of a network of well-dispersed platelets (or a few platelets), while in OLap, gelation results from a network of stacks of several platelets. NMR relaxation measurements indicate that gelation does not affect the average relaxation of water protons. However, T, increases marginally for the protons in the organic moieties in MLap and decreases for protons in the organic moieties in OLap. Relaxation measurements, analyses of line width, and NOESY taken together suggest that, in OLap, gelation is a consequence of association of the organic moieties on the laponite edges, and that this association strengthens with time. Thus, the time-dependent changes in NMR suggest a structural origin for the time-dependent changes in the rheological behavior.</p>1 aPatil, Suhas, P.1 aMathew, Renny1 aAjithkumar, Thalasseril, G.1 aRajamohanan, P., R.1 aMahesh, T., S.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/gelation-covalently-edge-modified-laponites-aqueous-media-1-rheology-and-nuclear-magnetic-002030nas a2200253   4500008004100000022001400041245006800055210006400123260012500187300001100312490000800323520114800331653001401479653002001493653002001513653001701533653001401550653002401564653001801588100003101606700002101637700002701658856009101685       2009                        eng d  a0021-960600aPolymer crystallization in the presence of ``sticky'' additives0 aPolymer crystallization in the presence of sticky additives  aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScAUG  a0749050 v1313 a<p>The effect of ``sticky'' additives (viz., those that have attractive interactions with the polymer) on polymer crystallization, has been investigated by dynamic Monte Carlo (DMC) simulations. Additive-polymer attractive interactions result in a slowing down of the polymer chain diffusivity in the melt state. Our results show that with increasing additive stickiness, polymer crystallinity decreases monotonically, and thinner crystallites form, viz., crystallization is inhibited by the presence of sticky additives. Unusually, the observed ``specific heat'' peak at the phase transition shows nonmonotonic behavior with additive stickiness, and exhibits a maximum for intermediate values of additive stickiness. While the origins of this unexpected behavior are not clear, we show that it correlates with a large interchange between crystalline and amorphous states of the monomers, in the vicinity of the additives. At this intermediate additive stickiness, we also find that crystallization follows a qualitatively different route-crystallinity shows a non-Avrami-like evolution, unlike the case at low or high additive stickiness.</p>10aAdditives10aamorphous state10acrystallisation10acrystallites10aDiffusion10aMonte Carlo methods10apolymer melts1 aDasmahapatra, Ashok, Kumar1 aNanavati, Hemant1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/polymer-crystallization-presence-sticky-additives-001953nas a2200181   4500008004100000022001400041245008300055210006900138260007100207300001400278490000800292520126200300100002501562700002701587700001701614700002801631856011201659       2009                        eng d  a1520-610600aSelf-assembly of silica particles in a nonionic surfactant hexagonal mesophase0 aSelfassembly of silica particles in a nonionic surfactant hexago  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAR  a3423-34300 v1133 a<p>We investigate the process of self-assembly, and the resultant structures in composites of silica particles with a hexagonal mesophase of a nonionic surfactant and water. We report a systematic transition in behavior when the particle size is increased relative to the characteristic mesophase spacing. Water dispersible cage-like silsesquioxanes that are molecular analogues of silica particles and are smaller than the mesophase spacing swell the space between the surfactant cylinders. Silica particles comparable to the characteristic hexagonal spacing partition into the hexagonal phase and into strandlike particulate aggregates. Even larger particles phase separate from the hexagonal phase to form particulate strands that organize with a mesh size comparable to the wavelength of visible light. This self-assembly is reversible and the particles disperse by breaking up the aggregates on heating the composite into the isotropic phase. On cooling from the isotropic phase into the hexagonal, the particles are expelled from the growing hexagonal domains and finally impinge to form strandlike aggregates. Unusually, the isotropization temperature is increased in the composites as the particles nucleate the formation of the hexagonal phase.</p>1 aSharma, Kamendra, P.1 aKumaraswamy, Guruswamy1 aLy, Isabelle1 aMondain-Monval, Olivier  uhttps://library.ncl.res.in/content/self-assembly-silica-particles-nonionic-surfactant-hexagonal-mesophase-001922nas a2200169   4500008004100000022001400041245011400055210006900169260007100238300001600309490000800325520121500333100002501548700002101573700002701594856013101621       2010                        eng d  a1520-610600aAdsorption of nonionic surfactant on silica nanoparticles: structure and resultant interparticle interactions0 aAdsorption of nonionic surfactant on silica nanoparticles struct  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcSEP  a10986-109940 v1143 a<p>Addition of nonionic surfactant, C(12)E(9), to an aqueous dispersion of charge stabilized silica nanoparticles renders particle aggregation reversible. In contrast, aggregation of the same silica particles in aqueous solutions is irreversible. We use a combination of small-angle X-ray scattering (SAXS) and contrast matching small-angle neutron scattering (SANS) to investigate interparticle interactions and microstructure in dispersions of silica particles in aqueous nonionic surfactant solutions. We show that the silica particles interact through a screened Coulombic interaction in aqueous dispersions; interestingly, this interparticle interaction is hard-sphere-like in surfactant solutions. In surfactant solutions, we show that the final surfactant-particle structure can be modeled as 14 micelles adsorbed (on average) on the surface of each silica particle. This gives rise to the short-range interparticle repulsion that makes particle aggregation reversible, and results in the hard sphere interparticle interaction potential. Finally, we show that adsorption of polyethylene imine on the surface of the silica particles prevents adsorption of surfactant micelles on the particle surface.</p>1 aSharma, Kamendra, P.1 aAswal, Vinod, K.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/adsorption-nonionic-surfactant-silica-nanoparticles-structure-and-resultant-interparticle-002591nas a2200229   4500008004100000022001400041245007700055210006900132260007100201300001400272490000700286520177200293100001702065700002502082700001802107700002202125700002402147700003202171700002502203700002702228856010602255       2010                        eng d  a0024-929700aVolume transition of PNIPAM in a nonionic surfactant hexagonal mesophase0 aVolume transition of PNIPAM in a nonionic surfactant hexagonal m  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAY  a4782-47900 v433 a<p>We investigate the volume transition of a thermoresponsive polymer, poly(N-isopropylacrylamide), PNIPAM, in the presence of an aqueous solution of nonionic surfactant, C(12)E(9). We combine turbidimetry with optical microscopy, NMR, and SAXS to follow the volume transition of the PNIPAM and the H(1)-isotropic transition of the surfactant/water system. Nonionic surfactants such as C(12)E(9) are known to interact weakly with PNIPAM. Accordingly, we show that there is only a small change in the volume transition temperature for the PNIPAM in isotropic micellar solutions of C(12)E(9), even for relatively high concentrations of C(12)E(9). Interestingly, once the surfactant forms an H(1) phase, there is a dramatic decrease in the coil globule transition onset temperature. We believe that this behavior results from a competition between C(12)E(9) in the H(1) phase, and PNIPAM to associate with water. When PNIPAM in the H(1) phase is cooled to low enough temperatures so as to be in the coil state, it locally disturbs the hexagonal phase ordering. Thus, we show that for PNIPAM in a weakly interacting surfactant matrix, it is the phase behavior of the matrix rather than the matrix chemistry that governs the coil globule transition. Finally, we show that in a PNIPAM copolymer with a higher LCST we observe an interesting sequence of transitions in the surfactant phase: on cooling from a high temperature free-blowing turbid globular state (similar to 75 degrees C), we enter a free-flowing translucent coil phase (similar to 47 degrees C), then a turbid gel (similar to 25 degrees C) where the copolymer is collapsed in the HI phase, and finally a low-temperature clear gel (similar to 5 degrees C) where the copolymer is in the expanded coil state.</p>1 aJijo, V., J.1 aSharma, Kamendra, P.1 aMathew, Renny1 aKamble, Samruddhi1 aRajamohanan, P., R.1 aAjithkumar, Thalasseril, G.1 aBadiger, Manohar, V.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/volume-transition-pnipam-nonionic-surfactant-hexagonal-mesophase-002631nas a2200217   4500008004100000022001400041245011400055210006900169260007100238300001400309490000800323520179600331100002502127700003002152700002202182700002102204700002402225700001502249700002702264856012202291       2011                        eng d  a1520-610600aAssembly of polyethyleneimine in the hexagonal mesophase of nonionic surfactant: effect of pH and temperature0 aAssembly of polyethyleneimine in the hexagonal mesophase of noni  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUL  a9059-90690 v1153 a<p>We investigate the dispersion of a pH responsive polymer, polyethyleneimine, PEI, in a hexagonal (H(1)) mesophase of a nonionic surfactant, C(12)E(9), and water, at pH ranging from basic (pH = 12.8) to acidic (pH = 1). While the C(12)E(9)/H(2)O phase behavior is independent of pH, we demonstrate that, in the PEI/C(12)E(9)/H(2)O system, changing the pH influences PEI-C(12)E(9) interactions, and thus, influences the isotropic-H(1) phase transition. With decrease in pH, there is increasing protonation of the PEI chain, and consequently, the chain extends. We show, using a combination of SAXs, optical microscopy and visual experiments, that the inclusion of PEI in a 1:1 surfactant water mixture, lowers the hexagonal-isotropic transition temperature, T. At higher pH = 12.8 T(HI) shows a pronounced decrease from SO to 13 degrees C on addition of PEI, and the PEI/C(12)E(9)/H(2)O system forms a transparent gel. At pH = 1, we observe qualitatively different behavior and an opaque gel forms below T(HI)= 25 degrees C. The isotropic-H(1) transition, in turn, influences the phase separation of PEI chains from the C(12)E(9)/H(2)O system. 2D NMR ROESY data provides evidence that there are strong surfactant PEI interactions at high pH that significantly reduce at lower pH. The NMR data is in accord with molecular dynamics simulations that show that surfactants strongly aggregate with unprotonated PEI chains, but not with fully protonated chains; thus, in this system, the pH controls a cascade of microstructural organization: increasing pH decreases chain protonation and increases polymer-surfactant interactions, resulting in suppression of the isotropic-H(1) transition to lower temperatures, thus, influencing the phase separation of PEI from the surfactant/water system.</p>1 aSharma, Kamendra, P.1 aChoudhury, Chandan, Kumar1 aSrivastava, Sonal1 aDavis, Hilda, C.1 aRajamohanan, P., R.1 aRoy, Sudip1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/assembly-polyethyleneimine-hexagonal-mesophase-nonionic-surfactant-effect-ph-and-001725nas a2200169   4500008004100000022001400041245009500055210006900150260006700219300001400286490000700300520105700307100001801364700002701382700002701409856011901436       2011                        eng d  a0032-388800aInfluence of DMDBS on the morphology and mechanical properties of polypropylene cast films0 aInfluence of DMDBS on the morphology and mechanical properties o  a111 RIVER ST, HOBOKEN 07030-5774, NJ USAbWILEY-BLACKWELLcOCT  a2013-20230 v513 a<p>We investigate extrusion film casting (EFC) of polypropylene (PP) and examine the effects of varying the concentration of nucleating agent, dimethyl dibenzylidene sorbitol (DMDBS); melt temperature at the die exit; and the draw ratio. Addition of DMDBS increases the PP crystallization temperature, and consequently the PP lamellar repeat spacing. For the draw ratios explored, we do not observe any substantial orientation of iPP crystals for films of neat iPP. However, addition of DMDBS results in the formation of oriented PP crystals, with greater orientation for higher draw ratios. On cooling from the melt, a network of DMDBS nanofibers forms in the PP. We believe that flow-alignment of this DMDBS network templates the orientation of PP crystals. We observe that the tensile modulus and yield stress increase with PP crystal orientation. However, at high DMDBS concentrations (0.8%), films have poor mechanical strength due to formation of voids and defects. POLYM. ENG. SCI., 51:2013-2023, 2011. (C) 2011 Society of Plastics Engineers</p>1 aSreenivas, K.1 aPol, Harshawardhan, V.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/influence-dmdbs-morphology-and-mechanical-properties-polypropylene-cast-films-001445nas a2200169   4500008004100000022001400041245008800055210006900143260007100212300001400283490000700297520079000304100001801094700002301112700002701135856011301162       2011                        eng d  a0024-929700aPhase separation of DMDBS from PP: effect of polymer molecular weight and tacticity0 aPhase separation of DMDBS from PP effect of polymer molecular we  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAPR  a2358-23640 v443 a<p>We report an unexpected dependence of DMDBS phase separation temperature on the molecular weight of the matrix isotactic polypropylene (iPP). DMDBS crystallizes out at lower temperatures for iPP with decreasing molecular weight (and correspondingly lower tacticity). All the iPPs in our study are reasonably high molecular weight samples and there is no molecular weight dependence of their solubility parameter. Therefore, the decrease in DMDBS phase separation temperature for lower molecular weights cannot be rationalized using thermodynamic arguments. This molecular weight dependence appears to be unique to isotactic polypropylene and is not observed for either syndiotactic polypropylene or for random copolymers of isotactic polypropylene containing ethylene comonomer.</p>1 aSreenivas, K.1 aBasargekar, Rajeev1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/phase-separation-dmdbs-pp-effect-polymer-molecular-weight-and-tacticity-001917nas a2200241   4500008004100000022001400041245014500055210006900200260007100269300001400340490000700354520100900361653001401370653001601384653001701400653001801417653001501435100002501450700002301475700002201498700002701520856012801547       2011                        eng d  a0897-475600aSelf-standing three-dimensional networks of nanoparticles with controllable morphology by dynamic templating of surfactant hexagonal domains0 aSelfstanding threedimensional networks of nanoparticles with con  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAPR  a1448-14550 v233 a<p>Assembly of nanoparticles into free-standing three-dimensional networks has implications for a wide range of applications. We show that dynamic templating of surfactant hexagonal domains is a facile technique to organize nanoparticles into a network of particulate strands. Dispersed particles (&gt; 10 nm), independent of particle chemistry, assemble into networks, when the surfactant matrix cools into the hexagonal phase. We demonstrate assembly of inorganic, polymeric, and protein nanoparticles into networks. Where particle assembly is reversible, particles are coated with polymers that are subsequently cross-linked to stabilize the networks after surfactant removal. This technique involves near ambient temperatures and a benign water wash for template removal. The network mesh size can be varied from submicrometers to tens of micrometers by controlling the cooling rate. Particle networks can be flow-oriented prior to cross-linking, and interpenetrating networks can also be formed.</p>10ahexagonal10amacroporous10ananoparticle10aself assembly10asurfactant1 aSharma, Kamendra, P.1 aGanai, Anal, Kumar1 aGupta, Sayam, Sen1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/self-standing-three-dimensional-networks-nanoparticles-controllable-morphology-dynamic-002219nas a2200193   4500008004100000022001400041245011400055210006900169260007100238300001600309490000700325520145100332100002001783700002001803700002101823700002701844700002201871856013201893       2011                        eng d  a0743-746300aSynthesis of poly-L-glutamic acid grafted silica nanoparticles and their assembly into macroporous structures0 aSynthesis of polyLglutamic acid grafted silica nanoparticles and  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcOCT  a12124-121330 v273 a<p>Polypeptide-coated silica nanoparticles represent an interesting class of organic inorganic hybrids since the ordered secondary structure of the polypeptide grafts imparts functional properties to these nanoparticles. The synthesis of a poly-L-glutamic acid (PLGA) silica nanoparticle hybrid by employing N-carboxyanhydride (NCA) polymerization to synthesize the polypeptide chains and Cu catalyzed azide alkyne cycloaddition reaction to graft these chains onto the silica surface is reported. This methodology enables the synthesis of well-defined polypeptide chains that are attached onto the silica surface at high surface densities. The PLGA-silica conjugate particles are well dispersed in water, and have been thoroughly characterized using multinuclear (C-13, Si-29) solid state NMR, thermogravimetric analysis, Fourier transform infrared, dynamic light scattering, and transmission electron microscopy. The pH-dependent reversible aggregation of the PLGA-silica particles, driven by the change in PLGA structure, has also been studied. Preliminary results on the use of aqueous dispersions of silica-PLGA for the preparation of three-dimensional macroporous structures with oriented pores by ice templating methodology are also demonstrated. These macroporous materials, comprising a biocompatible polymer shell covalently attached to rigid inorganic cores, adopts an interesting lamellar structure with fishbone-type architecture.</p>1 aKar, Mrityunjoy1 aPauline, Minois1 aSharma, Kamendra1 aKumaraswamy, Guruswamy1 aGupta, Sayam, Sen  uhttps://library.ncl.res.in/content/synthesis-poly-l-glutamic-acid-grafted-silica-nanoparticles-and-their-assembly-macroporous-002834nas a2200253   4500008004100000022001400041245009400055210006900149260007100218300001400289490000700303520192800310100002702238700002202265700001802287700002002305700001902325700002402344700001702368700003202385700002402417700001902441856012002460       2012                        eng d  a0024-929700aLamellar melting, not crystal motion, results in softening of polyoxymethylene on heating0 aLamellar melting not crystal motion results in softening of poly  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAUG  a5967-59780 v453 a<p>We probe temperature-dependent changes in the semicrystalline microstructure of polyoxymethylene using a combination of modulated DSC, SAXS, and solid-state NMR to characterize macroscopic behavior, lamellar-level structure, and molecular environments, respectively, and correlate these with the change in mechanical properties probed using DMA and AFM. Two model samples are investigated: a melt crystallized sample prepared by injection molding and a sample obtained by crystallization from dilute solution. Our investigations reveal that, for both samples, there is an increase in crystalline motions and in the amorphous content on heating. DMA and AFM measurements reveal that the modulus of the molded sample decreases on heating to about 100 degrees C; however, there is a significant difference in behavior of the solution crystals, where we observe no significant decrease in stiffness (from AFM measurements). Thus, in contrast to previous reports, we demonstrate that the decrease in modulus on heating polyoxymethylene does not correlate with chain motions in the crystalline regions. We use SAXS to probe the semicrystalline morphology for the samples on heating and show that, for the molded sample, there is a distribution of lamellar thickness at room temperature and that the thin lamellae in this distribution melt on heating. In contrast to the behavior of the melt crystallized samples, the solution crystals exhibit no change in the lamellar stacking on heating to 150 degrees C. We also demonstrate that, on heating, the amorphous regions in the solution crystals always appear to have restricted mobility while there are mobile and low mobility amorphous regions in the molded samples. Our results suggest that, contrary to conventional belief, the decrease in modulus on heating polyoxymethylene arises not from motions in the crystalline lamellae but primarily from melting of thin lamellae.</p>1 aKumaraswamy, Guruswamy1 aSurve, Nikita, S.1 aMathew, Renny1 aRana, Abhimanyu1 aJha, Saroj, K.1 aBulakh, Neelima, N.1 aNisal, Anuya1 aAjithkumar, Thalasseril, G.1 aRajamohanan, P., R.1 aRatnagiri, Ram  uhttps://library.ncl.res.in/content/lamellar-melting-not-crystal-motion-results-softening-polyoxymethylene-heating-001683nas a2200205   4500008004100000022001400041245011400055210006900169260007100238300001400309490000800323520088500331100001801216700002001234700001601254700002701270700002201297700002601319856013201345       2012                        eng d  a0002-786300aMultiple topologies from glycopolypeptide-dendron conjugate self-assembly: nanorods, micelles, and organogels0 aMultiple topologies from glycopolypeptidedendron conjugate selfa  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAPR  a7796-78020 v1343 a<p>Glycopolypeptides (GPs) were synthesized by ring-opening polymerization of glycosylated N-carboxyanhydride monomer and attached to hydrophobic dendrons at one chain end by ``click'' reaction to obtain amphiphilic anisotropic macromolecules. We show that by varying polypeptide chain length and dendron generation, an organogel was obtained in dimethylsulfoxide, while nanorods and micellar aggregates were observed in aqueous solutions. Assemblies in water were characterized by electron microscopy and dye encapsulation. Secondary structure of the GP chain was shown to affect the morphology, whereas the chain length of the poly(ethylene glycol) linker between the GP and dendron did not alter rod-like assemblies. Bioactive surface chemistry of these assemblies displaying carbohydrate groups was demonstrated by interaction of mannose-functionalized nanorods with ConA.</p>1 aPati, Debasis1 aKalva, Nagendra1 aDas, Soumen1 aKumaraswamy, Guruswamy1 aGupta, Sayam, Sen1 aAmbade, Ashootosh, V.  uhttps://library.ncl.res.in/content/multiple-topologies-glycopolypeptide-dendron-conjugate-self-assembly-nanorods-micelles-and-001259nas a2200205   4500008004100000022001400041245011400055210006900169260011000238300001400348490000700362520041800369100002300787700001900810700002500829700002100854700002700875700002200902856012900924       2012                        eng d  a1359-734500aSynthesis of functional hybrid silica scaffolds with controllable hierarchical porosity by dynamic templating0 aSynthesis of functional hybrid silica scaffolds with controllabl  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcMAR  a5292-52940 v483 a<p>We report a facile one-pot synthesis of hierarchically porous scaffolds, with independent control over nanoparticle mesoporosity and scaffold macroporosity. Our technique combines the chemistry of mesoporous silica nanoparticles with the control afforded by dynamic templating of surfactant mesophases. These materials are readily functionalizable and allow controllable spatial variation in macroporosity.</p>1 aGanai, Anal, Kumar1 aKumari, Sushma1 aSharma, Kamendra, P.1 aPanda, Chakadola1 aKumaraswamy, Guruswamy1 aGupta, Sayam, Sen  uhttps://library.ncl.res.in/content/synthesis-functional-hybrid-silica-scaffolds-controllable-hierarchical-porosity-dynamic-001822nas a2200193   4500008004100000022001400041245011000055210006900165260007100234300001600305490000800321520104600329100002501375700002301400700001701423700003001440700002701470856013101497       2013                        eng d  a1520-610600aExclusion from hexagonal mesophase surfactant domains drives end-to-end enchainment of rod-like particles0 aExclusion from hexagonal mesophase surfactant domains drives end  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcOCT  a12661-126680 v1173 a<p>Anisotropic rod-like particles assemble end-to-end when the surfactant/water matrix in which they are dispersed is cooled from the isotropic to the lyotropic hexagonal phase. We demonstrate the formation of such end-to-end assemblies for gold nanorods, which are tens of nanometers in size, as well as for micrometer-sized ellipsoidal polystyrene particles. In both cases, the particles are well-dispersed in the low-viscosity surfactant/water phase above the isotropic-H-1 transition temperature. On cooling into the H-1 phase, mesophase domains form and the particles are expelled to the isotropic phase. As the H-1 domains grow and finally impinge, the particles are localized at the domain boundaries where they reorient and assemble end-to-end. Remarkably, we observe the formation of end-to-end assemblies of gold nanorods even for volume fractions as low as 2 x 10(-6) in the initially dispersed state. The extent of particle ``enchainment'' increases with the particle concentration and with the aspect ratio of the particles.</p>1 aSharma, Kamendra, P.1 aGanai, Anal, Kumar1 aSen, Debasis1 aPrasad, Bhagavatula L. V.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/exclusion-hexagonal-mesophase-surfactant-domains-drives-end-end-enchainment-rod-particles-002834nas a2200253   4500008004100000022001400041245007900055210006900134260007100203300001400274490000700288520198600295653001402281653002002295653001302315653000802328653002602336653001802362100001902380700001902399700002702418700002202445856011302467       2013                        eng d  a0897-475600aLarge centimeter-sized macroporous ferritin gels as versatile nanoreactors0 aLarge centimetersized macroporous ferritin gels as versatile nan  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcDEC  a4813-48190 v253 a<p>Organized assemblies of bionanoparticles such as ferritin provides templates that can be exploited for nanotechnological applications. Organization of ferritin into well-defined three-dimensional assemblies is challenging and has attracted considerable attention recently. We have synthesized, for the first time, large (centimeter-sized) self-standing macroporous scaffold monoliths from ferritin bionanoparticles, using dynamic templating of surfactant H-1 domains. These scaffolds comprise three-dimensionally connected strands of ferritin, organized as a porous gel with porosity similar to 55 mu m. The iron oxide inside the ferritin scaffold can be easily replaced with catalytically active monodisperse zerovalent transition metal nanoparticles using a very simple protocol. Since the ferritin is cross-linked in the scaffold, it is significantly robust with enhanced thermal stability and better tolerance toward several organic solvents in Comparison to the native ferritin bionanoparticle. In addition, the scaffold macropores facilitate substrate and reagent transport and hence the monoliths containing active Pd or iron oxide nanoparticles inside apo-ferritin bionanoparticles were used as a recyclable heterogeneous catalyst for the oxidation of 2,3,6-trimethyl phenol to 2,3,6-trimethyl-1,4-benzoquinone (precursor for Vitamin E synthesis) and for Suzuki-Miyaura cross-coupling reaction in both aqueous and organic solvents. The protein shell around the nanoparticles protects them from agglomeration, a phenomenon that otherwise plagues nanoparticles-based catalysis. The presence of macropores allow the ferritin scaffold to act as catalytic monolith for continuous flow reactions having rapid reaction rates, while offering a low pressure drop. Finally, the Pd@apo-ferritin scaffold was immobilized inside a steel cartridge and used for the continuous flow hydrogenation of alkenes to their corresponding alkanes for 15 cycles without any loss of activity.</p>10acatalysis10acontinuous flow10aferritin10agel10amacroporous materials10aSelf-assembly1 aKumari, Sushma1 aKulkarni, Amol1 aKumaraswamy, Guruswamy1 aGupta, Sayam, Sen  uhttps://library.ncl.res.in/content/large-centimeter-sized-macroporous-ferritin-gels-versatile-nanoreactors-001926nas a2200169   4500008004100000022001400041245008500055210006900140260007100209300001400280490000700294520126500301100002301566700002101589700002701610856011901637       2013                        eng d  a0743-746300aNanoparticle size controls aggregation in lamellar nonionic surfactant mesophase0 aNanoparticle size controls aggregation in lamellar nonionic surf  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAUG  a9643-96500 v293 a<p>We show that the size of silica nanoparticles influences the nature of their aggregation in an aqueous solution of a relatively hydrophobic nonionic surfactant, C12E4. We present results for dispersions of silica nanopartides with sizes varying from 8 to 26 nm, in a 75: 25 C12E4/water system, that forms a lamellar phase, L-alpha, at room temperature. Addition of silica particles does not affect the formation of the L-alpha phase. Nanoparticles smaller than about 11 nm aggregate irreversibly in the C12E4/water system. However, nanoparticles larger than about 15 nm aggregate in the L-alpha phase, but are dispersed at temperatures above the L-alpha order-disorder temperature. Thus, in contrast to the smaller particles, aggregation of silica nanopartides larger than about 15 nm is reversible with temperature. We use small-angle neutron scattering (SANS) demonstrate that these results can be explained by the size-dependent wrapping of nanoparticles by surfactant bilayers. Larger particles, above 15 nm in size, are sterically stabilized by the formation of an adsorbed surfactant bilayer. The cost of bilayer bending inhibits adsorption onto the highly curved surfaces of smaller particles, and these ``bare'' particles aggregate irreversibly.</p>1 aVenugopal, Edakkal1 aAswal, Vinod, K.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/nanoparticle-size-controls-aggregation-lamellar-nonionic-surfactant-mesophase-001688nas a2200265   4500008004100000022001400041245009100055210006900146260007100215300001600286490000600302520077300308653001901081653001401100653002601114653001701140653001701157100002101174700002301195700002101218700002401239700002701263700001701290856011501307       2014                        eng d  a1944-824400aEnhancing cubosome functionality by coating with a single layer of poly-epsilon-lysine0 aEnhancing cubosome functionality by coating with a single layer   a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcOCT  a17126-171330 v63 a<p>We report the preparation and characterization of monoolein cubosomes that can be easily surface modified through adsorption of a single layer of cationic poly-epsilon-lysine. Poly-epsilon-lysine coated cubosomes show remarkable stability in serum solution, are nontoxic and, are readily internalized by HeLa cells. The poly-epsilon-lysine coating provides chemical handles for further bioconjugation of the cubosome surface. We also demonstrate that the initial release rate of a hydrophilic drug, Naproxen sodium, from the cubosomes is retarded with just a single layer of polymer. Interestingly, cubosomes loaded with Naproxen sodium, recently shown to have anticancer properties, cause more apoptosis in HeLa cells when compared to free unencapsulated drug.</p>10abioconjugation10acubosomes10adrug delivery vehicle10adual loading10atheranostics1 aDeshpande, Sonal1 aVenugopal, Edakkal1 aRamagiri, Shobha1 aBellare, Jayesh, R.1 aKumaraswamy, Guruswamy1 aSingh, Neetu  uhttps://library.ncl.res.in/content/enhancing-cubosome-functionality-coating-single-layer-poly-epsilon-lysine-001124nas a2200157   4500008004100000022001400041245010300055210006900158260007100227300000800298490000600306520048200312100001800794700002700812856012700839       2014                        eng d  a2161-165300aLarge amplitude oscillatory shear induces crystal chain orientation in velocity gradient direction0 aLarge amplitude oscillatory shear induces crystal chain orientat  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJAN  a6-90 v33 a<p>Imposition of large amplitude oscillatory shear (LAOS) on crystallizing polymer melts results in lamellar orientation in the shear gradient direction, in contrast to the flow-orientation observed for steady shear. LAOS enhances the formation of plate-like nuclei and orients their normals in the gradient direction. An Arrhenius temperature dependence (with activation energy approximate to 226 kJ/mol) characterizes the relaxation of crystal orientation with annealing.</p>1 aSreenivas, K.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/large-amplitude-oscillatory-shear-induces-crystal-chain-orientation-velocity-gradient-002558nas a2200229   4500008004100000022001400041245008900055210006900144260007100213300001400284490000700298520173600305100002302041700001802064700001802082700001902100700002002119700001702139700002202156700002702178856012302205       2014                        eng d  a0897-475600aSoft colloidal scaffolds capable of elastic recovery after large compressive strains0 aSoft colloidal scaffolds capable of elastic recovery after large  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcSEP  a5161-51680 v263 a<p>Assemblies of inorganic or glassy particles are typically brittle and cannot sustain even moderate deformations. This restricts the use of such materials to applications where they do not experience significant loading or deformation. Here, we demonstrate a general strategy to create centimeter-size macroporous monoliths, composed primarily (&gt;90 wt %) of colloidal particles, that recover elastically after compression to about one-tenth their original size. We employ ice templating of an aqueous dispersion of particles, polymer, and cross-linker such that cross-linking happens in the frozen state. This method yields elastic composite scaffolds for starting materials ranging from nanoparticles to micron-sized dispersions of inorganics or glassy lattices. The mechanical response of the monoliths is also qualitatively independent of polymer type, molecular weight, and even cross-linking chemistry. Our results suggest that the monolith mechanical properties arise from the formation of a unique hybrid microstructure, generated by cross-linking the polymer during ice templating. Particles that comprise the scaffold walls are connected by a cross-linked polymeric mesh. This microstructure results in soft monoliths, with moduli similar to O (10(4) Pa), despite the very high particle content in their walls. A remarkable consequence of this microstructure is that the monolith mechanical response is entropic in origin: the modulus of these scaffolds increases with temperature over a range of 140 K. We show that interparticle connections formed by cross-linking during ice templating determine the monolith modulus and also allow relative motion between connected particles, resulting in entropic elasticity.</p>1 aRajamanickam, Raja1 aKumar, Sushma1 aKumar, Deepak1 aGhosh, Shankar1 aKim, Jong, Chul1 aTae, Giyoong1 aGupta, Sayam, Sen1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/soft-colloidal-scaffolds-capable-elastic-recovery-after-large-compressive-strains-002005nas a2200169   4500008004100000245010700041210006900148260000800217300001600225490000700241520135300248100002601601700002301627700002701650700003001677856012801707       2014                        eng d00aUltrathin sheets of metal or metal sulfide from molecularly thin sheets of metal thiolates in solution0 aUltrathin sheets of metal or metal sulfide from molecularly thin  cMAY  a3436−34420 v263 a<p>Materials that exist as single molecule thick twodimensional sheets are in great demand because they hold promise as precursors for synthesis of layered functional materials. We demonstrate that metal thiolates, that exist as lamellar assemblies in the neat state, can be disassembled into individual molecular sheets simply by dilution in apolar organic solvents and that these can form ultrathin metallic layers on substrates upon heat treatment. We establish the pathway to the disassembly of metal thiolates in solution using a combination of techniques, including X-ray diffraction, light scattering, FTIR, and TEM. Our results indicate that the lamellar structure of Pd-thiolates is preserved in toluene up to a concentration of 300% w/v and the average intersheet distance is unchanged. Interestingly, the dynamics of the Pd-thiolate sheets remain correlated even on diluting them up to 30% w/v, though the disorder within the lamellar stacks increases with a decrease in their coherence length. Finally, at dilutions less than about 5% w/v, individual sheets of these structures can be accessed that are isolated and directly observed using TEM. Heat treatment of the ultrathin films of metal thiolates deposited on appropriate substrates resulted in the formation of metal or metal sulfides with retention of sheetlike morphologies.</p>1 aBusupalli, Balanagulu1 aKummara, Sreenivas1 aKumaraswamy, Guruswamy1 aPrasad, Bhagavatula L. V.  uhttps://library.ncl.res.in/content/ultrathin-sheets-metal-or-metal-sulfide-molecularly-thin-sheets-metal-thiolates-solution02476nas a2200205   4500008004100000022001400041245009900055210006900154260011000223300001400333490000700347520165000354100001702004700002402021700003002045700001502075700002602090700002702116856012702143       2015                        eng d  a1744-683X00aCompact polar moieties induce lipid-water systems to form discontinuous reverse micellar phase0 aCompact polar moieties induce lipidwater systems to form discont  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcMAY  a5417-54240 v113 a<p>The role of molecular interactions in governing lipid mesophase organization is of fundamental interest and has technological implications. Herein, we describe an unusual pathway for monoolein/water reorganization from a bicontinuous mesophase to a discontinuous reverse micellar assembly, directed by the inclusion of polar macromolecules. This pathway is very different from those reported earlier, wherein the Fd3m phase formed only upon addition of apolar oils. Experiments and molecular dynamics simulations indicate that hydrophilic ternary additives capable of inducing discontinuous phase formation must (i) interact strongly with the monoolein head group and (ii) have a compact molecular architecture. We present a detailed investigation that contrasts a monoolein-water system containing polyamidoamine (PAMAM) dendrons with one containing their linear analogs. The Fd3m phase forms only on the addition of PAMAM dendrons but not their linear analogs. Thus, the dendritic architecture of PAMAM plays an important role in determining lipid mesophase behavior. Both dendrons and their linear analogs interact strongly with monoolein through their amine groups. However, while linear polymers adsorb and spread on monoolein, dendrons form aggregates that interact with the lipid. Dendrons induce formation of an intermediate reverse hexagonal phase, which subsequently restructures into the Fd3m phase. Finally, we demonstrate that other additives with compact structures that are known to interact with monoolein, such as branched polyethylenimine and polyhedral silsesquioxane cages, also induce the formation of the Fd3m phase.</p>1 aKumar, Manoj1 aPatil, Naganath, G.1 aChoudhury, Chandan, Kumar1 aRoy, Sudip1 aAmbade, Ashootosh, V.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/compact-polar-moieties-induce-lipid-water-systems-form-discontinuous-reverse-micellar-001682nas a2200157   4500008004100000022001400041245008500055210006900140260011000209300001400319490000700333520102600340100001701366700002701383856011401410       2015                        eng d  a1744-683X00aPhase behaviour of the ternary system: monoolein-water-branched polyethylenimine0 aPhase behaviour of the ternary system monooleinwaterbranched pol  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcJUN  a5705-57110 v113 a<p>Addition of a branched polymer, polyethyleneimine, significantly alters the organization of a glycerol monooleate (GMO) lipid-water system. We present detailed data over a wide range of compositions (water content from 10 to 40%, relative to GMO and PEI fractions from 0 to 4%) and temperatures (25-80 degrees C). The PEI molecular weight effects are examined using polymers over a range from 0.8 to 25 kDa. Addition of PEI induces the formation of higher curvature reverse phases. In particular, PEI induces the formation of the Fd3m phase: a discontinuous phase comprising reverse micelles of two different sizes stacked in a cubic AB(2) crystal. The formation of the Fd3m phase at room temperature, upon addition of polar, water soluble PEI is unusual, since such phases typically are formed only upon addition of apolar oils. The largest stability window for the Fd3m phase is observed for PEI with a molecular weight = 2 kDa. We discuss how PEI influences the formation and stability of high curvature phases.</p>1 aKumar, Manoj1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/phase-behaviour-ternary-system-monoolein-water-branched-polyethylenimine-001913nas a2200169   4500008004100000022001400041245004100055210004100096260011000137300001000247490000800257520133000265100002701595700001801622700003001640856007301670       2016                        eng d  a1359-664000aColloidal assembly by ice templating0 aColloidal assembly by ice templating  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcOCT  a61-760 v1863 a<p>We investigate ice templating of aqueous dispersions of polymer coated colloids and crosslinkers, at particle concentrations far below that required to form percolated monoliths. Freezing the aqueous dispersions forces the particles into close proximity to form clusters, that are held together as the polymer chains coating the particles are crosslinked. We observe that, with an increase in the particle concentration from about 106 to 108 particles per ml, there is a transition from isolated single particles to increasingly larger clusters. In this concentration range, most of the colloidal clusters formed are linear or sheet like particle aggregates. Remarkably, the cluster size distribution for clusters smaller than about 30 particles, as well as the size distribution of linear clusters, is only weakly dependent on the dispersion concentration in the range that we investigate. We demonstrate that the main features of cluster formation are captured by kinetic simulations that do not consider hydrodynamics or instabilities at the growing ice front due to particle concentration gradients. Thus, clustering of colloidal particles by ice templating dilute dispersions appears to be governed only by particle exclusion by the growing ice crystals that leads to their accumulation at ice crystal boundaries.</p>1 aKumaraswamy, Guruswamy1 aBiswas, Bipul1 aChoudhury, Chandan, Kumar  uhttps://library.ncl.res.in/content/colloidal-assembly-ice-templating01911nas a2200169   4500008004100000022001400041245005100055210005100106260007100157300001400228490000700242520133200249100002801581700002201609700002701631856008301658       2016                        eng d  a0897-475600aOmniphilic polymeric sponges by ice templating0 aOmniphilic polymeric sponges by ice templating  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAR  a1823-18310 v283 a<p>Sponges that absorb a large quantity of solvent relative to their weight, independent of the solvent polarity, represent useful universal absorbents for laboratory and industrial spills. We report the preparation of macroporous polymer sponges by ice templating of polyethylenimine aqueous solutions and their cross-linking in the frozen state. The as-prepared monolith is hydrophilic and absorbs over 30 fold its weight in water. Modification of this sponge using valeroyl chloride renders it omniphilic; viz., a modified sponge absorbs over 10-fold its dry weight of either water or hexane. Modification using palmitoyl chloride that has a longer chain length results in the preparation of a hydrophobic sponge with a water contact angle around 130, which retains its oleophilicity underwater. The solvent absorbed in these sponges can be simply squeezed out, and the sponges are stable to several hundred cycles of compression. The large pore sizes of these sponges allow rapid absorption of even high viscosity solvents such as pump oil. Finally, we demonstrate that these sponges are also able to separate apolar oils that are emulsified in water using surfactants. These high porosity sponges with controllable solvophilicity represent inexpensive, high performance universal absorbents for general solvent spills.</p>1 aChatterjee, Soumyajyoti1 aGupta, Sayam, Sen1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/omniphilic-polymeric-sponges-ice-templating01975nas a2200169   4500008004100000245011700041210006900158260000800227300001600235490000700251520131000258100002101568700002201589700004301611700002701654856012401681       2016                        eng d00aTemplate determines whether chemically identical nanoparticle scaffolds show elastic recovery or plastic failure0 aTemplate determines whether chemically identical nanoparticle sc  cNOV  a11623-116300 v323 a<p>Subtle variations in the preparation of ice-templated nanoparticle assemblies yield monoliths that are chemically identical but exhibit qualitatively different mechanical behavior. We ice template aqueous dispersions to prepare macroporous monoliths largely comprising silica nanoparticles held together by a crosslinked polymer mesh. When the polymer is crosslinked in the presence of ice crystals, we obtain an elastic sponge that is capable of recovery after imposition of large compressive strains (up to 80%). If, however, the ice is lyophilized before the polymer is crosslinked, we obtain a plastic monolith that fails even for modest strains (less than 10%). The elastic sponge and the plastic monolith are chemically identical; they have the same organic content, the same ratio of polymer to crosslinker, and the same average crosslink density. Atomic force microscopy (AFM) was used to probe the local mechanical properties of the crosslinked polymer mesh. These measurements indicate that plastic monoliths dissipate significantly more energy and have a larger spatial variation in local mechanical response relative to the elastic sponges. We believe that this behavior might correlate with a wider spatial distribution of crosslinks in plastic scaffolds relative to elastic scaffolds.</p>1 aSuresh, Karthika1 aPatil, Shivprasad1 aRajamohanan, Pattuparambil, Ramanpilla1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/template-determines-whether-chemically-identical-nanoparticle-scaffolds-show-elastic02767nas a2200265   4500008004100000022001400041245005700055210005700112260000800169490000700177520201300184653001302197653002002210653002202230653001902252653001302271653000902284653002002293653001702313653000902330100002802339700001802367700002702385856008902412       2017                        eng d  a1744-683X00aCapillary uptake in macroporous compressible sponges0 aCapillary uptake in macroporous compressible sponges  cSEP0 v133 a<p><span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; background-color: rgb(248, 248, 248);">The capillarity-driven uptake of liquid in swellable, highly porous sponges is of significant industrial importance. Sponges prepared using polymers and their composites with carbon nanotubes and graphene have been reported, with extraordinary solvent uptake capacities and with the ability to separate oil from water. However, the effect of systematic variation of sponge characteristics on solvent uptake has not been investigated. Here, we report experiments that study capillary uptake in a variety of flexible, centimetre-sized macroporous cylindrical sponges. We used ice-templating to prepare a series of model macroporous sponges in which the porosity, modulus and composition were systematically varied. We investigated two kinds of sponge: (a) those composed purely of cross-linked polymers and (b) those prepared as composites of inorganic particles and polymers. Both kinds of sponge are flexible and exhibit elastic recovery after large compressive deformation. All sponges were characterized thoroughly with respect to their pore microstructure and elastic modulus. When one end of a sponge is plunged into a large reservoir, water rises through capillary action against gravity. We observed a transition from an inertial capillary regime, where the liquid column height rose linearly with time, t, to a viscous capillary regime, where the liquid height rose with time t(0.5). We showed that these results can be rationalized using analyses developed for rigid sponges. We combined differential momentum balance equations for uptake in rigid capillaries with the phenomenological Ergun-Forchheimer relations to account for the effect of the sponge microstructure. This approach works remarkably well in the viscous capillary regime and shows that capillary uptake is governed primarily by the total porosity and pore dimensions of soft sponges.</span></p>10aaerogels10aBuilding blocks10aCatalyst Supports10aContact-angels10aDynamics10aflow10aOrganic Liquids10aPorous-Media10aRise1 aChatterjee, Soumyajyoti1 aDoshi, Pankaj1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/capillary-uptake-macroporous-compressible-sponges02476nas a2200169   4500008004100000245010500041210006900146260000800215300001400223490000800237520182600245100001902071700002802090700002702118700003102145856013002176       2017                        eng d00aElastic compressible energy storage devices from ice templated polymer gels treated with polyphenols0 aElastic compressible energy storage devices from ice templated p  cFEB  a3270-32780 v1213 aDesign and fabrication of rechargeable energy storage devices that are robust to mechanical deformation is essential for wearable electronics. We report the preparation of compressible supercapacitors that retain their specific capacitance after large compression and that recover elastically after at least a hundred compression expansion cycles. Compressible supercapacitors are prepared using a facile, scalable method that readily yields centimeter-scale macroporous objects. We ice template a solution of polyethylenimine in green tea extract to prepare a macroporous cross-linked polymer gel (PG) whose walls are impregnated with green tea derived polyphenols. As the PG is insulating, we impart conductivity by deposition of gold on it. Gold deposition is done in two steps: first, silver nanoparticles are formed on the PG walls by in situ reduction by polyphenols and then gold films are deposited on these walls. Gold coated PGs (GPGs) were used as electrodes to deposit poly(3,4-ethylenedioxythiophene) as a pseudocapacitive material. The specific capacitance of PEDOT coated GPGs (PGPG) was found to be 253 F/g at 1 A/g. PGPG could be compressed and expanded over a hundred cycles without any suffering mechanical failure or loss of capacitative performance. The capacitance was found to be 243 F/g upon compressing the device to 25% of its original size (viz. compressive strain = 75%). Thus, even large compression does not affect the device performance. This device shows power and energy densities of 2715 W/kg and 22 Wh/kg, respectively, in the uncompressed state. The macroporous nature of PGPG makes it possible to fill the PGPG pores with gel electrolyte. We report that the gel electrolyte filled supercapacitor exhibited a specific capacitance of 200 F/g, which increased by 4% upon 75% compression.1 aDas, Chayanika1 aChatterjee, Soumyajyoti1 aKumaraswamy, Guruswamy1 aKrishnarnoorthy, Kothandam  uhttps://library.ncl.res.in/content/elastic-compressible-energy-storage-devices-ice-templated-polymer-gels-treated-polyphenols02213nas a2200157   4500008004100000245008000041210006900121260000800190300001600198490000600214520163600220100002801856700003101884700002701915856011301942       2017                        eng d00aFire-retardant, self-extinguishing inorganic/polymer composite memory foams0 aFireretardant selfextinguishing inorganicpolymer composite memor  cDEC  a44864-448720 v93 aPolymeric foams used in furniture and automotive and aircraft seating applications rely on the incorporation of environmentally hazardous fire-retardant additives to meet fire safety norms. This has occasioned significant interest in novel approaches to the elimination of fire-retardant additives. Foams based on polymer nano composites or based on fire-retardant coatings show compromised mechanical performance and require additional processing steps. Here, we demonstrate a one-step preparation of a fire-retardant ice-templated inorganic/polymer hybrid that does not incorporate fire-retardant additives. The hybrid foams exhibit excellent mechanical properties. They are elastic to large compressional strain, despite the high inorganic content. They also exhibit tunable mechanical recovery, including viscoelastic "memory". These hybrid foams are prepared using ice-templating that relies on a green solvent, water, porogen. Because these foams are predominantly comprised of inorganic components, they exhibit exceptional fire retardance in torch burn tests and are self-extinguishing. After being subjected to a flame, the foam retains its porous structure and does not drip or collapse. In micro-combustion calorimetry, the hybrid foams show a peak heat release rate that is only 25% that of a commercial fire-retardant polyurethanes. Finally, we demonstrate that we can use ice-templating to prepare hybrid foams with different inorganic colloids, including cheap commercial materials. We also demonstrate that ice-templating is amenable to scale up, without loss of mechanical performance or fire-retardant properties.1 aChatterjee, Soumyajyoti1 aShanmuganathan, Kadhiravan1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/fire-retardant-self-extinguishing-inorganicpolymer-composite-memory-foams02307nas a2200265   4500008004100000022001400041245010600055210006900161260000800230300001600238490000700254520141800261653001801679653002001697653002301717653001601740653001901756100001801775700002201793700002101815700002401836700002201860700002701882856013201909       2017                        eng d  a1936-085100aLinking catalyst-coated isotropic colloids into ``active'' flexible chains enhances their diffusivity0 aLinking catalystcoated isotropic colloids into active flexible c  cOCT  a10025-100310 v113 aActive colloids are not constrained by equilibrium: ballistic propulsion, superdiffusive behavior, or enhanced diffusivities have been reported for active Janus particles. At high concentrations, interactions between active colloids give rise to complex emergent behavior. Their collective dynamics result in the formation of several hundred particle-strong flocks or swarms. Here, we demonstrate significant diffusivity enhancement for colloidal objects that neither have a Janus architecture nor are at high concentrations. We employ uniformly catalyst-coated, viz. chemo-mechanically, isotropic colloids and link them into a chain to enforce proximity. Activity arises from hydrodynamic interactions between enchained colloidal beads due to reaction-induced phoretic flows catalyzed by platinum nanoparticles on the colloid surface. This results in diffusivity enhancements of up to 60% for individual chains in dilute solution. Chains with increasing flexibility exhibit higher diffusivities. Simulations accounting for hydrodynamic interactions between enchained colloids due to active phoretic flows accurately capture the experimental diffusivity. These simulations reveal that the enhancement in diffusivity can be attributed to the interplay between chain conformational fluctuations and activity. Our results show that activity can be used to systematically modulate the mobility of soft slender bodies.10aactive matter10aBrownian motion10acolloidal assembly10adiffusivity10aice templating1 aBiswas, Bipul1 aManna, Raj, Kumar1 aLaskar, Abhrajit1 aKumar, P., B. Sunil1 aAdhikari, Ronojoy1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/linking-catalyst-coated-isotropic-colloids-active-flexible-chains-enhances-their-diffusivity00335nas a2200121   4500008004100000245003000041210003000071260000800101300001200109490000700121100002700128856005800155       2017                        eng d00aLiving in the polymer age0 aLiving in the polymer age  cAPR  a333-3340 v221 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/living-polymer-age01893nas a2200193   4500008004100000245006700041210006700108260000800175300001200183490000700195520124100202100003401443700002901477700002401506700003201530700001701562700002701579856009301606       2017                        eng d00aMolecular motifs for additives that retard PEO crystallization0 aMolecular motifs for additives that retard PEO crystallization  cAUG  a857-8640 v573 a<p>We investigate the influence of several bifunctional phenol additives (resorcinol: RES, hydroquinone: HYD, p-hydroxybenzoic acid: PHBA, and p-nitrophenol: PNP) on the crystallization of matrix polymer, polyethyleneoxide. We employ solid state Nuclear Magnetic Resonance spectroscopy (NMR), Differential Scanning Calorimetry (DSC), optical microscopy, and Small Angle X-ray Scattering (SAXS) to investigate crystallization of the additivated PEO and compare with Density Functional Theory (DFT) calculations of additive-PEO interactions. Additive-polymer interactions are a function of the functional groups on the additive. Temperature-dependent spherulitic growth rate measurements from optical microscopy and SAXS lamellar long spacings indicate a distinct trend in the effect of additives on PEO crystallization. Change in PEO crystallization is most pronounced with PNP, followed by PHBA and finally RES and HYD. This trend correlates qualitatively with the binding energies of additive-PEO interactions from DFT studies. Our results suggest that DFT calculations might be a useful screening tool to evaluate the influence of additives on polymer crystallization. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers</p>1 aShrivastava, Sudhakar, Dinesh1 aEldho, Kavalakal, Mathai1 aRajamohanan, P., R.1 aAjithkumar, Thalasseril, G.1 aVanka, Kumar1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/molecular-motifs-additives-retard-peo-crystallization02341nas a2200229   4500008004100000245007100041210006900112260000800181300001400189490000800203520158700211100002101798700002701819700003101846700002701877700001901904700001501923700002801938700001801966700002401984856010302008       2017                        eng d00aNanoparticle assembly: a perspective and some unanswered questions0 aNanoparticle assembly a perspective and some unanswered question  cAPR  a1635-16410 v1123 aIn early 2016, the Royal Society of Chemistry arranged a meeting on the topic 'Nanoparticle Assemblies: from Fundamentals to Applications' which was hosted at IIT-Bombay, Mumbai. The meeting brought several leading nanoscience and nanotechnology researchers to India and is only the second Faraday Discussions meeting to have been held in the country. The papers presented at the meeting and the resulting active discussions have been summarized in a Faraday Discussion issue(1). The broad range of topics discussed at the meeting led to an understanding on where we stand in the field of nanoparticle assembly, and also enunciated some of the outstanding fundamental and practical issues that remain to be resolved before these ideas can be applied to practical situations. Driven by these ideas, here we focus on four topics/questions: (i) Can we achieve function-driven design of nanoparticle assemblies? (ii) What is the minimal information needed to build a desired assembly? (iii) How complex a structure can one build? How can one make it responsive? What are the relative roles of equilibrium versus dynamics in the assembly process, and are we at a point where we can now pursue active assembly as a viable mode for creating complex assemblies? (iv) What are the applications that are being targeted and what are the barriers to implementation? In this perspective, we do not present an exhaustive survey of the vast literature in this area, but indicate overarching themes/questions that require immediate attention, largely based on the discussions at the Mumbai meeting.1 aKumar, Sanat, K.1 aKumaraswamy, Guruswamy1 aPrasad, Bhagavatula, L. V.1 aBandyopadhyaya, Rajdip1 aGranick, Steve1 aGang, Oleg1 aManoharan, Vinothan, N.1 aFrenkel, Daan1 aKotov, Nicholas, A.  uhttps://library.ncl.res.in/content/nanoparticle-assembly-perspective-and-some-unanswered-questions01559nas a2200181   4500008004100000245011100041210006900152260000800221490000600229520085800235100002001093700003001113700002401143700002501167700002701192700003001219856012801249       2018                        eng d00aAccelerated in vitro model for occlusion of biliary stents: investigating the role played by dietary fibre0 aAccelerated in vitro model for occlusion of biliary stents inves  cNOV0 v43 aackground To develop a new accelerated in vitro model that has implications for investigating the mechanism of biliary stent occlusion and help in the development of new materials that can alleviate this problem.

Methods We employ a combination of reconstituted animal bile, bacteria and cellulose fibres optimised to reproducibly generate accelerated occlusion of stents, and produce occlusions that closely mimic those found in clinical studies.

Results Our model affords repeatable, highly accelerated occlusion (within 2–3 days, compared with between about a week to 2 months in previous models). Our results highlight the role of dietary fibre in blockage of stents and demonstrate their importance in the onset of occlusion.

Conclusions This accelerated model may have implications for developing biliary stents with enhanced patency.1 aSurwase, Sachin1 aBalakrishnan, Harishankar1 aAcharya, Subrat, K.1 aMakharia, Govind, K.1 aKumaraswamy, Guruswamy1 aPrasad, Bhagavatula L. V.  uhttps://library.ncl.res.in/content/accelerated-vitro-model-occlusion-biliary-stents-investigating-role-played-dietary-fibre02435nas a2200193   4500008004100000022001400041245009300055210006900148260000900217300001200226490000700238520175300245100001701998700002702015700002702042700002002069700002702089856012502116       2018                        eng d  a1744-683X00aAqueous dispersions of lipid nanoparticles wet hydrophobic and superhydrophobic surfaces0 aAqueous dispersions of lipid nanoparticles wet hydrophobic and s  cJAN   a205-2150 v143 a<p>Efficient delivery of aqueous sprays to hydrophobic surfaces is the key technological challenge in a wide variety of applications, including pesticide delivery to plants. To account for losses due to bouncing of pesticide sprays off hydrophobic leaf surfaces, a large excess of pesticide is typically employed, resulting in environmentally hazardous run-offs that contaminate soil and ground water. We demonstrate that aqueous dispersions of glycerol monooleate nanoparticles, called cubosomes, wet hydrophobic and superhydrophobic surfaces and adhere to them. Cubosomes comprise glycerol monooleate lipid molecules self-assembled into a double diamond cubic phase, that form stable aqueous dispersions that are sterically stabilized using amphiphilic block copolymers. We use high speed imaging to monitor the spreading and retraction of aqueous drops impinged on model hydrophobic substrates and on superhydrophobic lotus leaves. We show that cubosomes diffuse to hydrophobic substrates and reorganize to form a thin, approximate to 2 nm adsorbed lipid layer during the millisecond time scales that characterize drop impact. This adsorbed film drastically reduces the water contact angle, transforming the hydrophobic surface to hydrophilic, thus facilitating retention of the aqueous drop on the surface. Aqueous drops of cubosomes impinged at low velocities on inclined natural superhydrophobic lotus leaf surfaces do not roll off, unlike drops of water or surfactant solutions. When sprayed on inclined lotus leaves, corresponding to the case of high velocity drop impingement, cubosome dispersions form a continuous wetting film. Our results have important implications for efficient, environment-friendly delivery of pesticide sprays.</p>1 aKumar, Manoj1 aKulkarni, Mayuresh, A.1 aChembu, Narendiran, G.1 aBanpurkar, Arun1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/aqueous-dispersions-lipid-nanoparticles-wet-hydrophobic-and-superhydrophobic-surfaces02185nas a2200253   4500008004100000022001400041245011300055210006900168260000800237300001600245490000800261520131000269100001501579700001901594700001901613700002801632700001901660700001801679700002501697700002501722700002701747700003101774856012601805       2018                        eng d  a1932-744700aFluorinated nanocellulose-reinforced all-organic flexible ferroelectric nanocomposites for energy generation0 aFluorinated nanocellulosereinforced allorganic flexible ferroele  cJUL  a16540-165490 v1223 a<p>We report here enhanced ferroelectric crystal formation and energy generation properties of polyvinylidene fluoride (PVDF) in the presence of surface-modified crystalline nanocellulose. Incorporation of only 2-5 wt % fluorinated nanocellulose (FNC) in PVDF has been found to significantly induce polar beta/gamma-phase crystallization as compared to the addition of unmodified nanocellulose (carboxylated nanocellulose). A device made up of electrically poled PVDF/FNC composite films yielded 2 orders of magnitude higher voltage output than neat PVDF in vibrational energy harvesting. This remarkable increase in energy generation properties of PVDF at such a low loading of an organic natural biopolymer could be attributed to the tailored surface chemistry of nanocellulose, facilitating strong interfacial interactions between PVDF and FNC. Interestingly, energy harvesting devices fabricated from PVDF/FNC nanocomposites charged a 4.7 mu F capacitor at significantly faster rate and the accumulated voltage on capacitor was 3.8 times greater than neat PVDF. The fact that PVDF/FNC nanocomposites still retain a strain at break of 10-15% and can charge a capacitor in few seconds suggests potential use of these nanocomposites as flexible energy harvesting materials at large strain conditions.</p>1 aRam, Farsa1 aAmbone, Tushar1 aSharma, Aakash1 aMurugesan, Rajarathinam1 aKajale, Deepak1 aBorkar, Vivek1 aAli, Shaikh, Faruque1 aBalu, Praveen, Kumar1 aKumaraswamy, Guruswamy1 aShanmuganathan, Kadhiravan  uhttps://library.ncl.res.in/content/fluorinated-nanocellulose-reinforced-all-organic-flexible-ferroelectric-nanocomposites02351nas a2200181   4500008004100000022001400041245009500055210006900150260000800219300001400227490000700241520169600248100001701944700003201961700002601993700002702019856012302046       2018                        eng d  a0743-746300aLarge PAMAM dendron induces formation of unusual P4332 mesophase in monoolein/water system0 aLarge PAMAM dendron induces formation of unusual P4332 mesophase  cMAY  a6827-68340 v343 aCompact macromolecular dendrons have been shown to induce the formation of discontinuous inverse micellar assemblies with Fd3m symmetry in monoolein/water systems. Here, we demonstrate that a large PAMAM dendron (G5: fifth generation) induces the formation a very unusual mesophase with P4332 symmetry. This mesophase had previously been observed in monoolein/water systems only on addition of cytochrome C. The P4332 mesophase can be considered an intermediate phase between the bicontinuous Ia3d and discontinuous micellar mesophases. In this unusual phase, every third rod junction of the Ia3d mesophase is replaced with a spherical micelle. We present a detailed investigation of the phase behaviour of monoolein/water as a function of G5 concentration and temperature. Addition of 1% G5 in 85/15 monoolein/water system induces a transition from the L to Ia3d phase. Further increase in G5 concentration to above 2% induces the formation of the P4332 phase. Thus, incorporation of G5 yields a qualitatively different phase diagram when compared with incorporation of lower generation PAMAM dendrons (G2 – G4) in monoolein/water, where the reverse micellar Fd3m phase forms. PAMAM dendrons of all generations, G2 – G5, bear terminal amine groups that interact with the monoolein head group. The compact molecular architecture of the dendrons and these attractive interactions induce bending of the monoolein bilayer structure. For smaller dendrons, G2 – G4, this results in the formation of the Fd3m phase. However, the large size of the G5 dendron precludes this and a rare intermediate phase between the Ia3d and discontinuous micellar phase, the P4332 mesophase forms instead.1 aKumar, Manoj1 aPatil, Naganath, Ganapatara1 aAmbade, Ashootosh, V.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/large-pamam-dendron-induces-formation-unusual-p4332-mesophase-monooleinwater-system01782nas a2200169   4500008004100000022001400041245006700055210006700122260000800189300001100197490000600208520123700214100001901451700002701470700002001497856009501517       2018                        eng d  a2475-995300aModeling the universal viscoelastic response of polymer fibers0 aModeling the universal viscoelastic response of polymer fibers  cJUN  a0626010 v23 a<p>Polymer fibers, including natural silk and synthetic fibers, exhibit universal viscoelastic response. On stretching below yield, they show logarithmic stress decay. On unloading fibers with a glassy amorphous phase, the stress recovers. A simple phenomenological model accurately describes data from independent mechanical experiments and provides insights into the micro structural origins of the fiber response. Counter to intuition, the model indicates that it is the crystalline regions, rather than the amorphous glass, that deform first on stretching fibers at high strain rates. On holding a stretched fiber, stress decays as a consequence of relaxations in amorphous regions. Finally, unloading the fiber transfers stress from the amorphous to crystalline regions resulting in stress recovery. Model parameters correlate well with the fiber microstructure. Crystal and amorphous moduli from the model match those from x-ray diffraction. Activation energies for the temperature dependence of the peak relaxation time are similar to those reported in the literature. Thus, a simple model that invokes only crystal-amorphous coexistence can successfully model the mechanical response of a wide variety of polymer fibers.</p>1 aSharma, Aakash1 aKumaraswamy, Guruswamy1 aThakre, Shirish  uhttps://library.ncl.res.in/content/modeling-universal-viscoelastic-response-polymer-fibers02105nas a2200181   4500008004100000022001400041245010500055210006900160260000800229300001600237490000600253520144600259100002801705700001801733700001601751700002701767856012901794       2018                        eng d  a2046-206900aPreparation of macroporous scaffolds with holes in pore walls and pressure driven flows through them0 aPreparation of macroporous scaffolds with holes in pore walls an  cJAN  a24731-247390 v83 a<p>Controlling the pore architecture in macroporous scaffolds has important implications for their use as reactor packings and as catalyst supports. We report the preparation of a macroporous structure, where the pore walls are perforated by holes. These materials are prepared by modification of the ice-templating protocol developed in our group. We freeze a dispersion of colloidal silica, polymer and cross-linker in a water/acetonitrile medium and allow crosslinking to proceed in the frozen state. The presence of a small fraction of acetonitrile (varying between 1.6% to 6.4%) results in the formation of holes in the pore walls. Increasing the acetonitrile concentration changes the pore size distribution, and produces smaller pores on average. This also results in an increasing fraction of the wall area being covered by small pores, of the order of a few microns in size. Perforation of the walls by pores does not change the overall porosity or modulus of the scaffolds. However, the introduction of pores leads to a drastic reduction in the pressure drop required to pump liquid through the scaffolds. The observed residence time distribution (RTD) in the scaffolds is represented by two plug flow reactors (PFRs) in parallel. The RTD results indicate that increasing the hole fraction in the pore walls results in increased channelling which explains the aforementioned decreased pressure drop during pressure driven flow.</p>1 aChatterjee, Soumyajyoti1 aPotdar, Aditi1 aKuhn, Simon1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/preparation-macroporous-scaffolds-holes-pore-walls-and-pressure-driven-flows-through-them02769nas a2200217   4500008004100000022001200041245011000053210006900163260000800232300001600240490000700256520201100263100002102274700001902295700002102314700002602335700001602361700002302377700002702400856012402427       2018                        eng d  a743746300aSingle-particle tracking to probe the local environment in ice-templated crosslinked colloidal assemblies0 aSingleparticle tracking to probe the local environment in icetem  cAPR  a4603–46130 v343 a<p>We use single-particle tracking to investigate colloidal dynamics in hybrid assemblies comprising colloids enmeshed in a crosslinked polymer network. These assemblies are prepared using ice templating and are macroporous monolithic structures. We investigate microstructure-property relations in assemblies that appear chemically identical but show qualitatively different mechanical response. Specifically, we contrast elastic assemblies that can recover from large compressive deformations with plastic assemblies that fail on being compressed. Particle tracking provides insights into the microstructural differences that underlie the different mechanical response of elastic and plastic assemblies. Since colloidal motions in these assemblies are sluggish, particle tracking is especially sensitive to imaging artifacts such as stage drift. We demonstrate that the use of wavelet transforms applied to trajectories of probe particles from fluorescence microscopy eliminates stage drift, allowing a spatial resolution of about 2 nm. In elastic and plastic scaffolds, probe particles are surrounded by other particles—thus, their motion is caged. We present mean square displacement and van Hove distributions for particle motions and demonstrate that plastic assemblies are characterized by significantly larger spatial heterogeneity when compared with the elastic sponges. In elastic assemblies, particle diffusivities are peaked around a mean value, whereas in plastic assemblies, there is a wide distribution of diffusivities with no clear peak. Both elastic and plastic assemblies show a frequency independent solid modulus from particle tracking microrheology. Here too, there is a much wider distribution of modulus values for plastic scaffolds as compared to elastic, in contrast to bulk rheological measurements where both assemblies exhibit a similar response. We interpret our results in terms of the spatial distribution of crosslinks in the polymer mesh in the colloidal assemblies.</p>1 aSuresh, Karthika1 aSharma, D., K.1 aChulliyil, Ramya1 aSarode, Ketan, Dinkar1 aKumar, Ravi1 aChoudhary, Arindam1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/single-particle-tracking-probe-local-environment-ice-templated-crosslinked-colloidal02461nas a2200181   4500008004100000022001400041245010600055210006900161260000800230300001400238490000700252520181400259100001902073700001702092700002002109700002702129856012302156       2019                        eng d  a0024-929700aCharacterizing microvoids in regenerated cellulose fibers obtained from viscose and lyocell processes0 aCharacterizing microvoids in regenerated cellulose fibers obtain  cJUN  a3987-39940 v523 a<p>Regenerated cellulose fibers are among the most widely used bio-derived materials. Currently, there is great interest in transitioning from the traditional viscose process to the more environmentally friendly lyocell process for fiber production. Differences between the characteristics of viscose and lyocell fibers can be attributed to microstructural differences that arise due to differences in the processing techniques. Here, we use small-angle scattering to characterize the microvoids in regenerated cellulose fibers that might govern the onset of mechanical failure in these. In regenerated cellulose fibers, scattering of X-rays or neutrons at small angles is largely dominated by scattering from microvoids. We demonstrate that small angle X-ray scattering (SAXS) over the q range that is typical for most commercial instruments arises from Porod scattering from the microvoid surfaces, viz., the scattered intensity scales as q(-4). Therefore, it is not possible to extrapolate this data to lower q to obtain microvoid dimensions and volume fraction. We combine SAXS with medium-resolution small-angle neutron scattering to characterize the microvoids in regenerated cellulose fibers. Specifically, we compare fibers produced using the viscose process with those from the lyocell process. For both viscose and lyocell fibers, microvoids have a high aspect ratio and are elongated in the fiber direction. Also, the volume fraction occupied by the microvoids is comparable for viscose and lyocell fibers (0.04-0.05%). However, there are differences in the microvoid size: Microvoids are more highly oriented in lyocell fibers and have a larger average length and diameter compared with viscose fibers. This result might have important implications for understanding failure of these fibers.</p>
1 aSharma, Aakash1 aSen, Debasis1 aThakre, Shirish1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/characterizing-microvoids-regenerated-cellulose-fibers-obtained-viscose-and-lyocell04684nas a2200157   4500008004100000245010700041210006900148300001400217490000700231520406800238100002104306700002304327700002104350700002704371856012804398       2019                        eng d00aCritical role of processing on the mechanical properties of cross-linked highly loaded nanocomposites 0 aCritical role of processing on the mechanical properties of cros  a5955-59620 v523 a<p>Polymer <span class="hitHilite">nanocomposites</span> are frequently not at equilibrium-therefore, <span class="hitHilite">the</span> structure and <span class="hitHilite">properties</span> critically depend <span class="hitHilite">on</span> <span class="hitHilite">the</span> protocol followed in their preparation. Here, we demonstrate that <span class="hitHilite">the</span> elastic-brittle transition in <span class="hitHilite">highly</span> <span class="hitHilite">loaded</span> ice-templated polymer <span class="hitHilite">nanocomposites</span> is sensitively determined by <span class="hitHilite">the</span> conformation <span class="hitHilite">of</span> polymer chains during nanocomposite preparation. Macroporous polymer <span class="hitHilite">nanocomposites</span> are synthesized using two preparation pathways, both exhibiting minor modifications <span class="hitHilite">of</span> <span class="hitHilite">the</span> ice-templating method wherein an aqueous dispersion <span class="hitHilite">of</span> nanoparticles, polymers, and cross-linkers is frozen. In one method, <span class="hitHilite">the</span> matrix polymer is <span class="hitHilite">cross-linked</span> in <span class="hitHilite">the</span> presence <span class="hitHilite">of</span> ice, whereas in <span class="hitHilite">the</span> other method, <span class="hitHilite">the</span> ice is removed by freeze-drying before <span class="hitHilite">the</span> polymer is <span class="hitHilite">cross-linked</span>. Although all measurable structural metrics are practically identical for <span class="hitHilite">the</span> two composites, they exhibit qualitatively different <span class="hitHilite">mechanical</span> <span class="hitHilite">properties</span>. <span class="hitHilite">Nanocomposites</span> <span class="hitHilite">cross-linked</span> in <span class="hitHilite">the</span> presence <span class="hitHilite">of</span> ice show exceptional resilience, recovering elastically from large compression for very high nanoparticle loadings-in some instances, above 90% by weight. Here, <span class="hitHilite">the</span> <span class="hitHilite">critical</span> particle loading for <span class="hitHilite">the</span> elastic- brittle transition is dependent <span class="hitHilite">on</span> <span class="hitHilite">the</span> molecular weight <span class="hitHilite">of</span> <span class="hitHilite">the</span> polymer. In comparison, samples <span class="hitHilite">cross-linked</span> after freeze-drying appear structurally identical but turn brittle at much lower particle loadings (about 60% by weight), independent <span class="hitHilite">of</span> <span class="hitHilite">the</span> matrix polymer molecular weight. We rationalize these differences in terms <span class="hitHilite">of</span> <span class="hitHilite">the</span> conformational state <span class="hitHilite">of</span> <span class="hitHilite">the</span> polymer during cross- linking. In <span class="hitHilite">the</span> former case, polymer chains are in good solvent during nanocomposite preparation, while after lyophilization, they are in a poor solvent. <span class="hitHilite">The</span> large spatial extent <span class="hitHilite">of</span> well-solvated chains and chain-chain overlap during cross-linking results in <span class="hitHilite">the</span> formation <span class="hitHilite">of</span> intermolecular cross-links, and we obtain elastic <span class="hitHilite">nanocomposites</span> even at high nanoparticle loadings. In contrast, for chains in collapsed conformations in a bad solvent, chain connectivity during cross-linking is achieved only for much lower particle loadings. Our results reiterate that <span class="hitHilite">the</span> sensitivity <span class="hitHilite">of</span> polymer conformations to different <span class="hitHilite">processing</span> methods can result in large differences in <span class="hitHilite">properties</span>, even though their consequences <span class="hitHilite">on</span> structural characteristics are effectively indistinguishable.</p>
1 aSuresh, Karthika1 aChowdhury, Arindam1 aKumar, Sanat, K.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/critical-role-processing-mechanical-properties-cross-linked-highly-loaded-nanocomposites02650nas a2200217   4500008004100000022001400041245012400055210006900179260000900248300001100257490000700268520187900275653001202154653003002166653001902196653002602215653001202241100002102253700002702274856013102301       2019                        eng d  a0022-372700aEffect of electrostatic interactions on structure and mechanical properties of ice templated colloid-polymer composites0 aEffect of electrostatic interactions on structure and mechanical  cMAY   a2140020 v523 a<p>When an aqueous dispersion of negatively charged colloids, cationic polymer and crosslinker is frozen and the polymer is allowed to crosslink in the frozen state, we obtain a self-standing macroporous composite foam. This material is soft, despite the high concentration of colloids and yet is remarkably elastic to large compressive strains. In these macroporous composites, the pore walls comprise colloidal particles held within a crosslinked polymer network. Here, we investigate the effect of varying colloid- polymer interactions in pre-fabricated macroporous composites on their microstructure and mechanical properties. During preparation of the composite, cationic polymer adsorbs on the negatively charged colloids. We tune the surface charge of particles embedded in a macroscopic monolith by immersing the composites in water maintained at different pH. In this way, we tune polymer-particle interactions in the composite. We observe a sudden increase in interparticle distance and swelling of composite when pH is decreased below the particle's isoelectric point. Correspondingly, we observe reduction in Young's and shear moduli, compression strength and macroscopic energy dissipation. We did not observe any pH dependent changes in pure polymer sponges (prepared by ice templating and crosslinking a polymer solution that does not contain colloidal particles). Therefore, the pH dependent structural and mechanical property changes arise from the composite structure rather than purely from the crosslinked polymer. We believe that the reduction in mechanical stiffness when the polymer-particle interaction becomes repulsive is because of the reduction in interfacial contacts between particle and polymer. Therefore, the mechanical stiffness of ice templated composite is strongly influenced by interactions between the polymer and particle surface.</p>10acolloid10aelectrostatic interaction10aice templating10amechanical properties10aPolymer1 aSuresh, Karthika1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/effect-electrostatic-interactions-structure-and-mechanical-properties-ice-templated-colloid01239nas a2200181   4500008004100000022001400041245005900055210005200114260000900166300001200175490000700187520069100194100002100885700002100906700002700927700002200954856008100976       2019                        eng d  a1744-683X00aOn the sensitivity of alginate rheology to composition0 asensitivity of alginate rheology to composition  cJAN   a159-1650 v153 a<p>The linear response of alginate-phenyl boronic acid (Alg-PBA) esters shows a universal, composition-independent viscoelastic fluid-like behaviour. Reversible association of alginates governs their rheology at all compositions (viz. at all alginate concentrations and solution pH). However, their high strain behaviour is very sensitive to composition. Tuning composition affords liquids that neck to form filaments capable of being drawn to large elongations without failure. We interpret our data by invoking strain-dependent association and dissociation rates for the alginates. High association rates at high strain result in materials with viscoelastic liquid like behaviour.</p>1 aSuresh, Karthika1 aHaering, Marleen1 aKumaraswamy, Guruswamy1 aDiaz, David, Diaz  uhttps://library.ncl.res.in/content/sensitivity-alginate-rheology-composition02769nas a2200229   4500008004100000022001400041245013600055210006900191260000800260300001400268490000700282520195800289653002602247653001002273653002602283653001302309100001902322700002302341700002002364700002702384856012802411       2019                        eng d  a0969-023900aStructure-property relations in regenerated cellulose fibers: comparison of fibers manufactured using viscose and lyocell processes0 aStructureproperty relations in regenerated cellulose fibers comp  cAPR  a3655-36690 v263 a<p>Regenerated cellulose fibers are produced using two industrially dominant technologies: the viscose and lyocell processes. Here, we compare commercially available fibers, prepared using the viscose and lyocell processes. Single fibers are subjected to a variety of mechanical deformations to obtain stress-strain, stress relaxation and stress recovery data. These are fitted to a phenomenological model, whose parameters are interpreted in terms of the fiber semicrystalline microstructure. This simple model does not incorporate the complexities of semicrystalline microstructure. Rather, it represents structure in a semicrystalline polymer fiber in terms of an elastic crystalline phase that coexists with a viscoelastic Voigt-like glassy amorphous phase. Lyocell fibers are characterized by higher values of crystalline modulus relative to viscose. Lyocell fibers also have a higher amorphous phase modulus and a wider relaxation spectrum than viscose, suggesting that amorphous and crystalline phases are dispersed in close connectivity in lyocell. Viscose and lyocell fibers exhibit qualitative similarities in their mechanical response. On stretching, there is a transition in the stress-strain curve from a low strain elastic response at a critical value of strain. This critical strain has been incorrectly attributed to yielding of the fiber. We establish that this critical value corresponds to an apparent yield. When subjected to strains higher than this apparent yield point, the fibers develop a memory of the mechanical deformation. This memory decays slowly, logarithmically with time and is lost over about a day as the fiber structure transitions back to the original as spun fiber. Finally, we demonstrate that on wetting the fibers with water, there is an increase in the apparent yield strain for viscose fibers, but not for lyocell. We interpret these results in terms of the semicrystalline microstructure of the fibers.</p>
10amechanical properties10aModel10aRegenerated cellulose10aYielding1 aSharma, Aakash1 aNagarkar, Shailesh1 aThakre, Shirish1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/structure-property-relations-regenerated-cellulose-fibers-comparison-fibers-manufactured01753nas a2200241   4500008004100000022001400041245006800055210006600123260000800189300001400197490000600211520100700217653003801224653001801262653001801280653001201298100002001310700002201330700001601352700001801368700002701386856009801413       2019                        eng d  a2637-610500aThree-dimensional printing with waste high-density polyethylene0 aThreedimensional printing with waste highdensity polyethylene  cNOV  a3157-31640 v13 a<p>Fused filament fabrication (FFF) three-dimensional (3D) printing of semicrystalline polymers such as high density polyethylene (HDPE) is challenging because crystallization-induced shrinkage of the filament, as it cools, results in stresses that warp the printed part and debond it from the print substrate. Here, we demonstrate that waste-derived HDPE can be successfully 3D printed by (i) blending with a small fraction (&lt;0.5% by weight) of dimethyl dibenzylidene sorbitol (DMDBS) and (similar to 10%) linear low density polyethylene (LLDPE) and (ii) printing the object with a thin ``brim'' around it that is adhered to the print substrate using common polyvinyl acetate-based glue. We match our experimental results with FEM simulations that provide insight into the origin of the stresses developed during printing. Because HDPE forms a significant fraction of the plastic waste stream, conversion of waste-derived HDPE to 3D printing filament has important technological implications.</p>
10a3d printing polyethylene printing10apolymer blend10aRecyclability10awarpage1 aGudadhe, Aniket1 aBachhar, Nirmalya1 aKumar, Anil1 aAndrade, Prem1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/three-dimensional-printing-waste-high-density-polyethylene02470nas a2200229   4500008004100000022001400041245009700055210006900152260000800221300000800229490000700237520171300244653001601957653002701973653001202000100002202012700002002034700001602054700001802070700002702088856012502115       2020                        eng d  a0250-470700a3D printing of semicrystalline polypropylene: towards eliminating warpage of printed objects0 a3D printing of semicrystalline polypropylene towards eliminating  cJUL  a1710 v433 a<p>Fused filament fabrication (FFF) is an extrusion-based 3D printing technique for thermoplastic polymers. In this technique, molten polymer is extruded through a print nozzle and is laid down layer by layer to build up the printed object. Currently, FFF is used primarily to print amorphous or low-crystallinity polymers, such as acrylonitrile butadiene styrene copolymer (ABS) or polylactic acid (PLA). Printing of semicrystalline polymers, such as polyethylene or polypropylene remains particularly challenging. During FFF of semicrystalline polymers, large thermomechanical stresses are generated when the polymer solidifies on cooling. These stresses result in warpage of the printed part. Here, we analyse the factors that influence stresses generated during FFF 3D printing of a commercial semicrystalline polymer, isotactic polypropylene. We investigate the effect of height of the printed object on part warpage, as well the effect of infilling during printing. We demonstrate that the stresses generated during FFF can be substantially decreased by incorporation of a `brim', viz. a thin layer at the base of the printed object, and by adhering the brim to the print substrate using common polyvinyl acetate-based glue. We systematically investigate the effect of the brim size on the warpage of the printed object. We support our experimental findings with finite element method (FEM) simulations that explain the mechanism of stress buildup during printing. The trend in stresses calculated in the FEM simulations parallel the warpage measured in the experiments. Thus, this work represents an important methodological advance towards warpage-free FFF printing of semicrystalline polymers.</p>
10a3D printing10apolypropylene printing10awarpage1 aBachhar, Nirmalya1 aGudadhe, Aniket1 aKumar, Anil1 aAndrade, Prem1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/3d-printing-semicrystalline-polypropylene-towards-eliminating-warpage-printed-objects02372nas a2200193   4500008004100000022001400041245014400055210006900199260000900268300001100277490000800288520163500296100002701931700002101958700001601979700002801995700002602023856012902049       2020                        eng d  a0021-897900aIce templated nanocomposites containing rod-like hematite particles: Interplay between particle anisotropy and particle-matrix interactions0 aIce templated nanocomposites containing rodlike hematite particl  cJUL   a0347020 v1283 a<p>We demonstrate that the mechanical response of ice templated nanocomposite scaffolds prepared from ellipsoidal hematite particles is determined by both the particle aspect ratio and the interaction between the particles and the matrix polymer. We ice template aqueous dispersions of hematite particles, polyethyleneimine, and diepoxy crosslinker and crosslink the polymer in the frozen state. This protocol results in the formation of elastic macroporous monoliths capable of complete recovery from large compressive strains. Hematite particles show an inversion of their surface charge with pH: they are negatively charged at a basic pH and positively charged under acidic conditions. This allows us to change the interaction between hematite particles and crosslinked matrix polymer that they are embedded in, simply by immersing the monoliths in aqueous solutions with different pH's. We report that under basic conditions, viz, when polyethyleneimine adsorbs on the particle surface, there is a decrease in the monolith modulus with an increase in the particle aspect ratio. We demonstrate that this correlates with a change in the mechanism of monolith response: from wall compression for isotropic particles to wall bending for anisotropic particles with an aspect ratio of 4. Under acidic conditions (pH=2), where hematite particles show a positive zeta potential, the monolith modulus increases with the aspect ratio of the ellipsoidal fillers. Understanding the interplay between filler aspect ratio and filler-matrix interaction has important implications for the control of nanocomposite mechanical properties.</p>
1 aKumaraswamy, Guruswamy1 aSuresh, Karthika1 aLama, Hisay1 aBasavaraj, Madivala, G.1 aSatapathy, Dillip, K.  uhttps://library.ncl.res.in/content/ice-templated-nanocomposites-containing-rod-hematite-particles-interplay-between-particle02816nas a2200217   4500008004100000022001400041245011000055210006900165260000800234300001400242490000700256520204500263653001802308653003402326653001702360653002602377100001902403700002002422700002702442856012902469       2020                        eng d  a0969-023900aMicrostructural differences between Viscose and Lyocell revealed by in-situ studies of wet and dry fibers0 aMicrostructural differences between Viscose and Lyocell revealed  cFEB  a1195-12060 v273 a<p>Regenerated cellulose fibers manufactured using Lyocell and Viscose processes exhibit differences in their structural response to mechanical deformation. Here, we study the effect of stretching and stress relaxation on the orientation of crystal and amorphous phases. Our results show that on stretching, orientation in both crystal and amorphous phases increases linearly with strain, correlating with the increase in stress and with the stretching of the crystalline unit cell along the c-axis. On holding after stretching to a particular strain, the stress relaxes logarithmically in time, correlating with a decrease in the strain along the c-axis of the crystal unit cell. The stress relaxation is also correlated with a logarithmic increase in amorphous orientation, while crystalline orientation stays constant. We attribute the stress development during stretching to deformation of the crystal unit cell, while crystal reorientation in the fiber direction results in increase in the crystalline orientation parameter. On holding the fiber at a fixed total strain, the stress relaxes as strain is transferred from crystal to amorphous regions. Thus, the strain on the unit cell c-axis decreases and amorphous orientation increases. There are quantitative differences between the rate of increase in amorphous phase orientation during stress relaxation for Lyocell and Viscose fibers. For dry fibers, Lyocell shows a slower increase in orientation during stress relaxation. On wetting the fibers, their structural response changes qualitatively. We combine wide angle x ray diffraction and birefringence experiments with our model to infer that that on stretching the wet fiber, the crystalline phase is neither strained nor oriented. However, orientation develops in the amorphous phase. During stress relaxation in wet condition, Lyocell fibers shows a faster increase in amorphous orientation than Viscose fibers, in line with the comparison of relaxation time spectra for wet Viscose and Lyocell fibers. Graphic abstract</p>
10abirefringence10aCrystal-amorphous orientation10aIn-situ WAXD10aRegenerated cellulose1 aSharma, Aakash1 aThakre, Shirish1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/microstructural-differences-between-viscose-and-lyocell-revealed-situ-studies-wet-and-dry02665nas a2200193   4500008004100000022001400041245005300055210005300108260000900161300001400170490000700184520208800191100001802279700001802297700002302315700002102338700002702359856008502386       2021                        eng d  a1744-683X00aColloidal assembly by directional ice templating0 aColloidal assembly by directional ice templating  cAPR   a4098-41080 v173 a<p>We investigate directional ice templating of dilute aqueous colloidal particle dispersions and examine the nature of the assemblies that result. We coat micron-size polystyrene colloids with cross-linkable polymer (polyethyleneimine, PEI), add cross-linker, and subject this dispersion to unidirectional freezing. We work at sufficiently low colloid concentrations, such that the particles do not percolate on freezing. When the aqueous dispersion freezes, ice crystals force polymer-coated particles and cross-linker into close proximity. This results in the formation of cross-linked clusters of particles at ice crystal boundaries. We vary the particle volume fraction from phi similar to 2.5 x 10(-3) to phi similar to 5.0 x 10(-2) and observe that there is a transition from isolated single particles to increasingly large sized clusters. Most of the clusters formed under these conditions are either linear, two-particle wide chains, or sheet-like aggregates. The probability (P-n) of clusters containing n particles (n &gt; 2) obeys a power law P-n similar to n(-eta), where eta strongly depends on the particle concentration in the dispersion, varying from 2.10 (for phi similar to 5.0 x 10(-2)) to 3.03 (for phi similar to 2.5 x 10(-3)). This change in eta is qualitatively different from the case of isotropic freezing, where eta is particle concentration-independent and depends only on the ice nucleation density. To understand the differences between isotropic and directional ice templating, we performed lattice simulations of a highly simplified model, where ice crystals grow at a constant rate to force clustering. We ignore hydrodynamic interactions and ice growth instabilities. Despite ignoring these experimental details, the simulations capture the experimental results, nearly quantitatively. As the ice crystals grow and the space available to the colloids ``closes up'' so that the particles cluster to form aggregates, crystallization protocol-induced differences in the geometry of these ``closed up'' spaces determine the scaling behaviour of P-n.</p>1 aBiswas, Bipul1 aMisra, Mayank1 aBisht, Anil, Singh1 aKumar, Sanat, K.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/colloidal-assembly-directional-ice-templating02152nas a2200253   4500008004100000022001400041245015200055210006900207260000800276300001400284490000700298520126500305653001201570653001601582653002701598653002201625653002101647100001501668700001801683700001701701700002701718700003101745856012201776       2021                        eng d  a0969-023900aElastic piezoelectric aerogels from isotropic and directionally ice-templated cellulose nanocrystals: comparison of structure and energy harvesting0 aElastic piezoelectric aerogels from isotropic and directionally   cJUL  a6323-63370 v283 a<p>We report the preparation of highly compressible and elastic piezoelectric aerogels of carboxylated cellulose nanocrystals (CNCs). Aqueous CNC dispersions containing polyethyleneimine and crosslinker were frozen isotropically to yield isotropic aerogels, while oriented aerogels were prepared by directional freezing. These aerogels were highly flexible and porous (similar to 85% void fraction), exhibiting greater than 90% recovery at 50% compressive strain even after 100 compression-decompression cycles. Since such aerogels with low bulk modulus and high anisotropy would be an ideal platform for leveraging the piezoelectric properties of CNCs, we used them to prepare piezoelectric nanogenerator devices and determined their energy transduction behavior. Anisotropic aerogels led to an enhanced open-circuit voltage of 840 mV (at similar to 8 N applied force), which is over 2.6 times higher than isotropic aerogels (320 mV). The energy density of anisotropic aerogels was around 52 nW/cm(2), representing outstanding piezoelectric performance for cellulose-based aerogels. Such aerogels with high compressibility, elastic recovery and exceptional piezoelectric performance could have potential applications in sensors, wearable electronics, etc.</p>10aAerogel10aAnisotropic10aCellulose nanocrystals10aenergy harvesting10aPiezoelectricity1 aRam, Farsa1 aBiswas, Bipul1 aTorris, Arun1 aKumaraswamy, Guruswamy1 aShanmuganathan, Kadhiravan  uhttps://library.ncl.res.in/content/elastic-piezoelectric-aerogels-isotropic-and-directionally-ice-templated-cellulose02445nas a2200241   4500008004100000022001400041245013500055210006900190260000900259300001600268490000700284520158700291653002901878653002201907653001901929653001801948100001501966700002101981700001702002700002702019700003102046856012602077       2021                        eng d  a0272-884200aHighly compressible ceramic/polymer aerogel-based piezoelectric nanogenerators with enhanced mechanical energy harvesting property0 aHighly compressible ceramicpolymer aerogelbased piezoelectric na  cJUN   a15750-157580 v473 a<p>Ceramic piezoelectric materials have orders of magnitude higher piezoelectric coefficients compared to polymers. However, their brittleness precludes imposition of large strains in mechanical energy harvesting applications. We report here that ice templating affords low bulk modulus lead-free aerogel piezoelectric nanogenerators (PENG) with unprecedented combination of flexibility and high piezoelectric response (voltage and power density). A modified ice templating protocol was used to fabricate piezoelectric nanocomposites of surface modified BaTiO3 (BTO) nanoparticles in crosslinked polyethylene imine. This protocol allowed incorporating a significantly high fraction of BTO particles (up to 83 wt %) in the aerogel, while retaining remarkably high compressibility and elastic recovery up to 80% strain. The output voltage, at an applied compressive force of 20 N (100 kPa), increased with BTO loading and a maximum output voltage of 11.6 V and power density of 7.22 ?W/cm2 (49.79 ?W/cm3) was obtained for PENG aerogels containing 83 wt% BTO, which is orders of magnitude higher than previously reported values for foam-based piezoelectric energy harvesters. The BTO/PEI PENGs also showed cyclic stability over 900 cycles of deformation. PENGs with higher porosity showed better elastic recovery and piezoelectric properties than lower porosity and higher BTO content aerogels. To the best of our knowledge, this is the first report to demonstrate the piezoelectric properties of high ceramic content aerogels having very high compressibility and elastic recovery.</p>10aCeramic polymer aerogels10aenergy harvesting10aice templating10apiezoelectric1 aRam, Farsa1 aSuresh, Karthika1 aTorris, Arun1 aKumaraswamy, Guruswamy1 aShanmuganathan, Kadhiravan  uhttps://library.ncl.res.in/content/highly-compressible-ceramicpolymer-aerogel-based-piezoelectric-nanogenerators-enhanced03020nas a2200289   4500008004100000022001400041245013500055210006900190260000900259300001400268490000600282520205800288653001702346653002502363653001102388653001202399653002302411653002602434653000902460100001902469700002402488700002002512700002302532700002002555700002702575856012802602       2021                        eng d  a2637-610500aProcess-induced microstructure in viscose and lyocell regenerated cellulose fibers revealed by SAXS and SEM of acid-etched samples0 aProcessinduced microstructure in viscose and lyocell regenerated  cMAY   a2598-26070 v33 a<p>Regenerated cellulose fibers represent an important class of bioderived commercial fibers. The traditional viscose process requires the use of environmentally harmful carbon disulfide solvent to produce fibers. Lyocell fibers, produced using a more sustainable recent process, exhibit differences in properties from viscose. These differences arise from their semicrystalline microstructure, formed during fiber spinning. It is widely believed that regenerated cellulose fibers predominantly form fringed fibrillar crystals. We optimize acid etching, followed by SEM as an experimental tool to visualize this fibrillar structure. Acid etching provides sufficient topological contrast to directly visualize similar to O(10 nm) fibrils using field-emission scanning electron microscopy (SEM). We combine SEM with small-angle X-ray scattering (SAXS) to reveal other microstructural details. We observe a Bragg peak, indicating the coexistence of stacked lamellar structure with crystalline fibrils for viscose fibers, but not for lyocell. Viscose and lyocell fibers are characterized by partially oriented semicrystalline microstructure. We present a methodology to calculate the Lorentz correction for such microstructure and employ this to analyze the lamellar scattering from viscose fibers using a 1D correlation function approach. We characterize the lamellar microstructure after swelling viscose fibers with water and observe expansion of the Bragg spacing due to water absorption in the amorphous regions. Our data suggest that the water-induced plasticization of amorphous regions is inhomogeneous. Lamellar stacks that are more misoriented from the fiber direction exhibit lower swelling than those along the fiber direction. The experimental methods described in this work reveal interesting details of semicrystalline microstructure in regenerated cellulose fibers, with important implications for the mechanical response of dry and wet fibers. The methods developed here might find use in investigations of other polymer fibers as well.</p>10aacid etching10acrystalline lamellae10afibers10afibrils10aLorentz correction10aRegenerated cellulose10aSAXS1 aSharma, Aakash1 aWankhede, Parnashri1 aSamant, Roopali1 aNagarkar, Shailesh1 aThakre, Shirish1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/process-induced-microstructure-viscose-and-lyocell-regenerated-cellulose-fibers-revealed02123nas a2200193   4500008004100000245010300041210006900144260000800213300001600221490000700237520143400244100001801678700002001696700001401716700001701730700002301747700002701770856013201797       2021                        eng d00aRigidity dictates spontaneous helix formation of thermoresponsive colloidal chains in poor solvent0 aRigidity dictates spontaneous helix formation of thermoresponsiv  cDEC  a19702-197110 v153 aThe formation of helical motifs typically requires specific directional interactions. Here, we demonstrate that isotropic interparticle attraction can drive self-assembly of colloidal chains into thermo-reversible helices, for chains with a critical level of backbone rigidity. We prepare thermoresponsive colloidal chains by cross-linking PNIPAM microgel-coated polystyrene colloids (“monomers”), aligned in an AC electric field. We control the chain rigidity by varying cross-linking time. Above the LCST of PNIPAM, there is an effective attraction between monomers so that the colloidal chains are in a bad solvent. On heating, the chains decrease in size. For the most rigid chains, the decrease is modest and is not accompanied by a change in shape. Much less rigid chains form relatively compact structures, resulting in a large increase in the local monomer density. Unusually, chains with intermediate rigidity spontaneously assemble into helical structures. The chain helicity increases with temperature and plateaus above the collapse transition temperature of the microgel particles. We simulate a minimal model that captures the spontaneous emergence of the helical conformations of the polymeric chain and provides insight into this shape transition. Our work suggests that a purely mechanical instability for semiflexible filaments can drive helix formation, without the need to invoke directional interactions.1 aBiswas, Bipul1 aMitra, Debarshi1 aKP, Fayis1 aBhat, Suresh1 aChatterji, Apratim1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/rigidity-dictates-spontaneous-helix-formation-thermoresponsive-colloidal-chains-poor-solvent01642nas a2200145   4500008004100000245006900041210006900110260000800179490000700187520112800194100002501322700002101347700002701368856010101395       2021                        eng d00aSlip behavior during pressure driven flow of Laponite suspension0 aSlip behavior during pressure driven flow of Laponite suspension  cMAY0 v333 a<p><span style="font-family: Lora, serif; font-size: 20px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400;">We investigate pressure driven pipe flow of Laponite suspension, as a model thixotropic fluid. The tendency of the suspension to age is controlled by addition of sodium chloride salt to vary the ionic strength. We use a syringe pump to prescribe the flow and observe that a steady state flow is obtained. Unusually, the steady state pressure drop required to maintain a constant flow rate decreases with an increase in the flow rate, in qualitative contrast to the expectation for Poiseuille flow. We demonstrate that experimental results obtained by varying the flow rate, salt concentration, and flow geometry (pipe diameter and length) can be collapsed onto a single universal curve that can be rationalized by invoking slip of the suspension at the tube walls. The Laponite suspension exhibits plug-like flow, yielding at the tube walls. Our results suggest that the slip length varies linearly with the flow rate and inversely with the tube diameter.</span></p>1 aKamdi, Prophesar, M.1 aOrpe, Ashish, V.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/slip-behavior-during-pressure-driven-flow-laponite-suspension01965nas a2200253   4500008004100000022001400041245011400055210006900169260000800238300001400246490000600260520113300266653001301399653000901412653001801421653001701439653001901456100001801475700002001493700002201513700002401535700002701559856012501586       2023                        eng d  a2637-610500aPolyethylene-grafted sheet-like silsesquioxane nanocomposites with unprecedented adhesion to polar substrates0 aPolyethylenegrafted sheetlike silsesquioxane nanocomposites with  cJUL  a5972-59830 v53 a<p>
	Polyethylene is a highly apolar polymer with very pooradhesionto most substrates, necessitating the use of tie layers. Therefore,the synthesis of functional polyethylene is a long-standing challengein catalytic ethylene polymerization. Here, we report the preparationof a nanocomposite comprising polyethylene covalently grafted ontosheet-like silsesquioxanes, with unprecedented adhesion to metal andglass. A norbornene-grafted, layered Mg-silsesquioxane is treatedwith Grubbs second-generation catalyst (G-II), and the identity ofcovalently tethered G-II is unambiguously ascertained. Covalentlytethered G-II catalyzes the ring opening metathesis polymerizationof cyclooctene to poly(cyclooctene). The resulting poly(cyclooctene)is catalytically hydrogenated to yield polyethylene. This polyethylenenanocomposite exhibited a bonding strength of the order of 100 MPaon stainless steel and aluminum, 10-fold higher than reported forengineered polyethylene copolymers. The nanocomposite exhibits anincrease in the polar component of surface energy, yet remains compatibleand cocrystallizes with a polyethylene matrix.</p>
10aadhesion10aclay10aNanocomposite10aPolyethylene10asilsesquioxane1 aSharma, Vivek1 aPaulbudhe, Uday1 aBachhar, Nirmalya1 aChikkali, Samir, H.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/polyethylene-grafted-sheet-silsesquioxane-nanocomposites-unprecedented-adhesion-polar02521nas a2200265   4500008004100000022001400041245007300055210006900128260000800197300001400205490000600219520170800225653000901933653002001942653001801962653001701980653001901997100001802016700002002034700001802054700002702072700002402099700002702123856010502150       2025                        eng d  a2637-610500aThermal properties of polyethylene-grafted sheetlike silsesquioxanes0 aThermal properties of polyethylenegrafted sheetlike silsesquioxa  cMAR  a4290-43000 v73 a<p>
	Polyethylene-grafted layered silsesquioxanes, termed polyethylene-clays (PEC), are nanocomposites comprising polyethylene chains tethered to inorganic sheets with a phyllosilicate-like structure. Here, we report that these nanocomposites show two-stage crystallization on cooling, qualitatively different from previous reports on polyethylene nanocomposites. We employ differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) to study the melting and crystallization of PEC. End tethering of the polyethylene chains to a nanosheet strongly influences the manner in which PEC crystallizes from the melt on cooling. PEC exhibits two-step crystallization, characterized by a sharp high-temperature exotherm, followed by a broader exotherm at lower temperatures, in contrast to a single sharp exotherm for neat polyethylene. SAXS indicates that lamellar stacks form at high temperatures and that the low-temperature exotherm corresponds to the formation of additional lamellae and their insertion within these stacks. PEC exhibits lower peak melting temperature, lower crystallinity, and a wider melting range relative to polyethylene. We show that the progress of crystallization of PEC is determined by its ultraslow relaxation dynamics. In contrast, PEC in xylene solution exhibits a significantly shorter relaxation time than the melt PEC. Such systems exhibited a single exotherm on cooling and SAXS structure factor peaks with peak positions in a ratio of 1:2. We hypothesize that the high melt viscosity inhibits the crystallization-induced decrease in the specific volume of PEC, resulting in tensile internal stresses that determine the observed thermal behavior.</p>
10aclay10aCrystallization10aNanocomposite10aPolyethylene10asilsesquioxane1 aSharma, Vivek1 aPaulbudhe, Uday1 aGupta, Poonam1 aZalte, Akshat, Shirish1 aChikkali, Samir, H.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/thermal-properties-polyethylene-grafted-sheetlike-silsesquioxanes