01922nas 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

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.

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-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

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.

1 aVenugopal, Edakkal1 aAswal, Vinod, K.1 aKumaraswamy, Guruswamy uhttps://library.ncl.res.in/content/nanoparticle-size-controls-aggregation-lamellar-nonionic-surfactant-mesophase-002100nas a2200301 4500008004100000022001400041245012500055210006900180260009500249300001200344490000800356520102200364653003201386653001901418653002601437653000901463653000901472653001801481653003301499100001701532700001901549700002101568700002401589700001801613700001501631700002101646856013101667 2014 eng d a0021-979700aEffect of self-assembly on triiodide diffusion in water based polymer gel electrolytes: an application in dye solar cell0 aEffect of selfassembly on triiodide diffusion in water based pol a525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USAbACADEMIC PRESS INC ELSEVIER SCIENCEcJUL a110-1170 v4253 a

The preparation of ordered polymer gels from the amphiphilic block copolymers, Pluronic (R) F77, P123 and polyethylene glycol in the presence of ionic liquid, iodine and organic additives is presented. At 35%(w/w) concentration these copolymers (F77 and P123) self-assembled into cubic liquid crystalline phase in aqueous solution and characterized by using SAXS and AFM measurements. The effects of micellar aggregation formed by polymers on the ionic transport and triiodide diffusion have been studied by electro-chemistry and SANS experiments. The ionic migration or triiodide diffusion through these polymer gels is found to be affected by the PEO/PPO content in the polymer backbone. These gels were successfully employed as an electrolyte in a dye sensitized solar cell. A remarkable solar to electricity conversion efficiency and good stability was obtained using Pluronic (R) F77 based gel, which is attributed to its thermoreversible sol to gel transition. (C) 2014 Elsevier Inc. All rights reserved.

10aAmphiphilic block copolymer10aDye solar cell10aMicellar nanochannels10aSANS10aSAXS10aSelf-assembly10aWater based gel electrolytes1 aSoni, S., S.1 aFadadu, K., B.1 aVekariya, R., L.1 aDebgupta, Joyashish1 aPatel, K., D.1 aGibaud, A.1 aAswal, Vinod, K. uhttps://library.ncl.res.in/content/effect-self-assembly-triiodide-diffusion-water-based-polymer-gel-electrolytes-application-001765nas a2200229 4500008004100000022001400041245012100055210006900176260007700245300001400322490000800336520087100344653002301215653003201238653001301270653002301283653003301306100002001339700002101359700002601380856012901406 2014 eng d a1022-135200aEffect of the branching pattern of hydrophobic dendrons on the core structure of linear-dendritic copolymer micelles0 aEffect of the branching pattern of hydrophobic dendrons on the c aBOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcAUG a1456-14650 v2153 a

Hydrophobic dendrons based on different branching patterns, viz. 3,5-di- and 3,4,5-trisubstituted phenyl rings, consist of the same backbone but exhibit different sizes, shapes, and hydrophobic densities. These dendrons are attached to poly(ethylene glycol) and the core properties of the copolymer micelles are investigated in tetrahydrofuran (THF)/water mixtures by neutron scattering. Two polymers with intermediate hydrophobicity are studied further with variations in the solvent composition and the temperature. The aggregation numbers for 3,4,5-based dendron copolymers are lower, with more THF molecules of solvation compared with the 3,5-based dendron copolymer, the difference being greater at higher generations due to different molecular shapes. The micellar core size increases in small steps with dendron size so that dye encapsulation is tuned.

10adiblock copolymers10alinear-dendritic copolymers10amicelles10aneutron scattering10astructure-property relations1 aKalva, Nagendra1 aAswal, Vinod, K.1 aAmbade, Ashootosh, V. uhttps://library.ncl.res.in/content/effect-branching-pattern-hydrophobic-dendrons-core-structure-linear-dendritic-copolymer-001955nas a2200217 4500008004100000022001400041245007700055210006900132260000800201300001400209490000700223520124600230100001701476700001701493700002101510700002601531700003501557700002101592700001701613856010701630 2016 eng d a1525-779700aSilk fibroin-sophorolipid gelation: deciphering the underlying mechanism0 aSilk fibroinsophorolipid gelation deciphering the underlying mec cOCT a3318-33270 v173 a

Silk fibroin (SF) protein, produced by silkworm Bombyx mori, is a promising biomaterial, while sophorolipid (SL) is an amphiphilic functional biosurfactant synthesized by nonpathogenic yeast Candida bombicola. SL is a mixture of two forms, acidic (ASL) and lactonic (LSL), which when added to SF results in accelerated gelation of silk fibroin. LSL is known to have multiple biological functionalities and hence hydrogels of these green molecules have promising applications in the biomedical sector. In this work, SANS, NMR, and rheology are employed to examine the assembling properties of individual and mixed SLs and their interactions with SF to understand the mechanism that leads to rapid gelation. SANS and NMR studies show that ASL assembles to form charged micelles, while LSL forms micellar assemblies and aggregates of a mass fractal nature. ASL and LSL together form larger mixed micelles, all of which interact differently with SF. It is shown that preferential binding of LSL to SF causes rapid unfolding of the SF chain leading to the formation of intermolecular beta sheets, which trigger fast gelation. Based on the observations, a mechanism for gelation of SF in the presence of different sophorolipids is proposed.

1 aDubey, Parul1 aKumar, Sugam1 aAswal, Vinod, K.1 aRavindranathan, Sapna1 aRajamohanan, Pattuparambil, R.1 aPrabhune, Asmita1 aNisal, Anuya uhttps://library.ncl.res.in/content/silk-fibroin-sophorolipid-gelation-deciphering-underlying-mechanism02000nas a2200301 4500008004100000022001400041245009700055210006900152260000900221300000900230490000800239520101400247653001501261653004401276653000701320653001701327653003501344653001701379100001701396700001701413700002601430700002201456700002101478700003501499700001701534700002101551856012601572 2018 eng d a0254-058400apH dependent sophorolipid assemblies and their influence on gelation of silk fibroin protein0 apH dependent sophorolipid assemblies and their influence on gela cJAN  a9-160 v2033 a

Sophorolipid (SL), a bio-derived surfactant is an excellent gelling agent for natural fibrous protein, silk fibroin (SF) leading to potential biomedical applications. Interaction of SF with SL has been shown to accelerate the formation of hydrogel with the rate being dependent on the form of SL used. Here, we examine the effect of pH on SL-SF interaction and gel formation by employing rheology, fluorescence spectroscopy, SANS and NMR. The results indicate that the size of SL assemblies decrease as pH increases from acidic to alkaline and significantly impacts the association of SL and SF. The association of SF and SL is mainly via hydrophobic interactions, with the SL molecules forming bead like structures along the SF chain. The increased charge on the acidic form of SL at higher pH results in greater repulsion between acidic SL molecules, which are bound to the hydrophobic sites of SF, leading to rapid chain unfolding and subsequent gelation. (C) 2017 Elsevier B.V. All rights reserved.

10aAssemblies10aNuclear magnetic resonance spectroscopy10apH10aSilk fibroin10aSmall angle neutron scattering10aSophorolipid1 aDubey, Parul1 aKumar, Sugam1 aRavindranathan, Sapna1 aVasudevan, Sahana1 aAswal, Vinod, K.1 aRajamohanan, Pattuparambil, R.1 aNisal, Anuya1 aPrabhune, Asmita uhttps://library.ncl.res.in/content/ph-dependent-sophorolipid-assemblies-and-their-influence-gelation-silk-fibroin-protein01670nas a2200205 4500008004100000022001400041245009800055210006900153260000800222300001600230490000700246520095900253100002201212700001501234700002101249700002101270700001701291700002601308856013001334 2019 eng d a0743-746300aSilk fibroin-sodium dodecyl sulfate gelation: molecular, structural, and rheological insights0 aSilk fibroinsodium dodecyl sulfate gelation molecular structural cNOV a14870-148780 v353 a

A gelling agent is necessary to accelerate sol to gel transition in an aqueous solution of silk fibroin (SF), which otherwise takes several days to complete. In this paper, we investigate the mechanism of gelation of Bornbyx mori SF by a model anionic surfactant, sodium dodecyl sulfate (SOS). Even though interactions between SDS and proteins have been extensively investigated, most of these studies have focused on globular proteins, which undergo denaturation. The interaction with a fibrous protein such as SF is different and results in an altered secondary structure leading to gelation. In this work, the concentration-dependent gelation process of the SF-SDS system is examined using rheology, SANS, FTIR, and NMR. We observed preferential binding of SDS to specific regions on the SF chain, which aids structural changes favoring beta-sheet formation. We propose a mechanism for the accelerated sol-gel transition in the SF-SDS system.

1 aHirlekar, Swarali1 aRay, Debes1 aAswal, Vinod, K.1 aPrabhune, Asmita1 aNisal, Anuya1 aRavindranathan, Sapna uhttps://library.ncl.res.in/content/silk-fibroin-sodium-dodecyl-sulfate-gelation-molecular-structural-and-rheological-insights01752nas a2200193 4500008004100000022001400041245007200055210006900127260000800196300001600204490000600220520113300226100002201359700001501381700002101396700002501417700001701442856009901459 2020 eng d a2470-134300aLauric acid sophorolipid: accelerating the gelation of silk fibroin0 aLauric acid sophorolipid accelerating the gelation of silk fibro cNOV a28571-285780 v53 a

Silk fibroin (SF) hydrogels find wide applications in tissue engineering. However, their scope has been limited due to the long gelation time in ambient conditions. This paper shows the reduction in gelation time of silk fibroin to minutes upon doping with a newly synthesized lauric acid sophorolipid (LASL). LASL comprises a fatty acid, lauric acid (with a 12-carbon aliphatic chain), that is derivatized by glucose molecules using a non-pathogenic yeast Candida bombicola. LASL was characterized using spectroscopic (Fourier transform infrared spectroscopy) and chromatographic (high-performance liquid chromatography, thin-layer chromatography, and high-resolution mass spectrometry) methods. This gelation of SF is comparable to the effect of an anionic surfactant, sodium dodecyl sulfate (SDS). The microstructure of SF-LASL hydrogels was investigated by small-angle neutron scattering (SANS) measurements and exhibited the beads-on-a-necklace model. The rheological properties of these hydrogels show similarity to SF-SDS hydrogels, therefore presenting a greener alternative for tissue engineering applications.

1 aHirlekar, Swarali1 aRay, Debes1 aAswal, Vinod, K.1 aPrabhune, Asmita, A.1 aNisal, Anuya uhttps://library.ncl.res.in/content/lauric-acid-sophorolipid-accelerating-gelation-silk-fibroin