GULMI CHAKRABORTY | UNIVERSITY OF NORTH BENGAL (original) (raw)

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Papers by GULMI CHAKRABORTY

The present report was undertaken due to the scarcity of information regarding the microstructura... more The present report was undertaken due to the scarcity of information regarding the microstructural transition from aqueous to acetonitrile (ACN)-based non-aqueous reverse micelles (RMs) stabilized by cationic didodecyldimethylammonium bromide (DDAB) and anionic sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in cyclohexane. The synergistic solubilization capacity of corresponding polar solvent at a fixed composition and the nature of conductance plots in these RMs were markedly varied along with the composition of binary solvents (water and ACN at pure or mixed states) and the surfactant charge types (DDAB and AOT). The structural alteration in these RMs through water- and ACN-rich compositions were studied by FTIR, where the results were explained in terms of molecular states of water and ACN inside RMs. The differential binding affinity of both polar solvents with the two surfactants was shown using ab initio calculations. The subsequent appearance and disappearance of aqueous nano-...

The surface property of the cationic micelles of cetyltrimethylammonium bromide (CTAB) in an aque... more The surface property of the cationic micelles of cetyltrimethylammonium bromide (CTAB) in an aqueous medium is highly modified in the presence of tyrosineoctyl ester (TYOE) and tyrosinedodecyl ester (TYDE), the models for aromatic amino acid side chains of transmembrane proteins. While the synergistic interaction between the quaternary ammonium head group of CTAB and the π-electron cloud of aromatic amino acid ester is influenced by the relative orientation and the unusual molecular geometry of the latter, this eventually triggers a morphology transition of the spherical micelle to cylindrical/wormlike micelles and imparts a strong viscoelasticity in the medium. Physical characteristics of the elongated micelles have been investigated by high resolution transmission electron microscopy (HRTEM) and the small angle neutron scattering (SANS) technique; the complex fluidic nature of the system is investigated by a dynamic rheological measurement. The intermolecular interactions have bee...

Journal of Molecular Liquids

Journal of Macromolecular Science, Part A

The journal of physical chemistry. B, Mar 1, 2018

Langmuir : the ACS journal of surfaces and colloids, Jan 5, 2017

Hydrophobic derivatives of tyrosine and tryptophan, viz. octyl and dodecyl esters of tyrosine and... more Hydrophobic derivatives of tyrosine and tryptophan, viz. octyl and dodecyl esters of tyrosine and octyl ester of tryptophan, are synthesized, and the interfacial and bulk properties in aqueous media are investigated as models for the membrane proteins. Molecular modeling by the density functional theory method is carried out to understand the molecular conformation and geometry for the purpose of determining the packing parameters. Water-induced molecular folding of the esters of both tyrosine and tryptophan, as observed using rotating frame nuclear Overhauser effect spectroscopy, indicates that the segregation of the hydrophobic and hydrophilic blocks in water is the key to the development of fascinating interfacial property displayed by the aromatic amino acid esters. The unusually high-order morphology of the aggregates, as observed using high-resolution transmission electron microscopy, is highly uncommon for single-chain amphiphiles and points to the fact that the self-assembly...

Journal of Polymer Research, 2016

Encyclopedia of Biocolloid and Biointerface Science 2V Set, 2016

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2016

RSC Adv., 2016

Efficient soft chemical nanoreactors: a design strategy to improve the performance of a model C–C... more Efficient soft chemical nanoreactors: a design strategy to improve the performance of a model C–C cross coupling (Heck) reaction under nanoscopic confinement of surfactant blends.

The nature of transition from ordinary micelles (of nanometer length scale) of surface active ion... more The nature of transition from ordinary micelles (of nanometer length scale) of surface active ionic liquid 1-Hexadecyl-3-methylimidazolium chloride, to wormlike micelles (WLM) (micrometer length scale), mediated by hydroxy aromatic π-electron systems 1-Naphthol, 2-Naphthol and 2,3-Dihydroxynaphthalene (2,3-DHN) in salt free condition have been studied under Newtonian as well as non-Newtonian flow regimes. Conductance and tensiometry show that the additives lower the CMC of the ionic liquid. The interaction parameter (β) of the systems at different mole fraction evaluated on basis of Rubingh’s Regular solution approach were negative at all SAIL/Additive compositions. UV-Vis spectroscopy showed that micelle-bound additives formed hydrogen bonds with interfacial water molecules. Increase in steady state fluorescence anisotropic measurements revealed that the additives increasingly partitioned within the micelles. 1H-NMR study confirmed that although the additives reside at the palisade layer, they perturb the micellar core as well. At higher concentration (100mM, 1:1), systems formed transparent viscoelastic gel. Rheological study of the viscoelastic gels showed that their zero shear viscosity is a function of temperature. 2,3-DHN interacted most strongly with the SAIL micelles, both in Newtonian and non-Newtonian regimes. This was corroborated by DFT study of binding energy. Hydrogen bonding of the hydroxy functionality along with strong cation-π interaction between the aromatic moieties and the imidazolium ring are considered as the main driving forces behind the morphology change. The viscosity of C16-3-MeImCl/1-Naphthol increased as function of salt concentration unlike C16-3-MeImCl/NaSal system. A possible mechanism is suggested and discussed. The present study sheds light on understanding the molecular interactions behind the structural change from spherical to elongated micelles, in both microscopic and macroscopic scale, triggered by hydroxy naphthalenes under salt-free condition. The metal tolerance of the gels has huge application prospects as fractured fluids in oil-mining industry.

The intrinsic viscosities [η] of poly(vinyl alcohol)s (PVAs, which are biocompatible polymers)—wi... more The intrinsic viscosities [η] of poly(vinyl alcohol)s (PVAs, which are biocompatible polymers)—with different (high, medium, and low) molecular weights were measured at 293–303 K in water (good solvent)–acetone (ACE, poor solvent) and water–tetrahydrofuran (THF, poor solvent) mixtures. The results observed, particularly the values of the Hug-gins constant (K H), indicated that the solvency of each PVA varied as a function of solvent composition (Φ ACE /Φ THF) and temperature. The unperturbed dimensions (K θ) of the PVAs under nontheta conditions in a variety of water–acetone and water–tetrahydrofuran solutions were also calculated using various equations. The values of K θ obtained via three different equations, i.e., those of Burchard–Stockmayer–Fixman (BSF), Berry, and Inagaki–Suzuki–Kurata (ISK), agreed well except for a few solvent compositions. The molecular extension factor (α n) and actual end-to-end distance (α n K θ) of each PVA were also computed.

Organized assemblies in aqueous and non-aqueous media based on mixed surfactants are one of the d... more Organized assemblies in aqueous and non-aqueous media based on mixed surfactants are one of the desired areas for experimental studies and carrying out chemical reactions due to synergistic performance and efficient solvents for various substrates. In this report, a model C–C cross coupling Heck reaction between n-butyl acrylate and 4-iodo-toluene is performed both in micelles and water/oil microemulsion systems as reaction media using a similar set of surfactants, [cetyltrimethylammonium bromide (CTAB) and polyoxyethylene (20) cetyl ether (C 16 E 20)], in their single and mixed states for the first time. In order to explain the possible location and mechanism of reaction in these media, multitechnique approaches are employed to understand the mutual interactions between surfactant(s) and other constituents in pure and mixed states at air–water as well as oil–water interfaces. A synergistic interaction is evidenced experimentally for a mixed CTAB/C 16 E 20 micellar system, which is also supported by theoretical calculations using density functional theory (DFT). The yield of Heck product in different media follows the order water < pure micelle < mixed micelle, which indicates a significant role of the confined environment of the aggregated systems. Further, mixed microemulsions including constituents of the formulations 1-pentanol and n-heptane or n-decane are explored as nanoreactors for carrying out such a reaction. Reaction yield in mixed water-in-oil (w/o) systems as a function of different hydration levels has been correlated with formation and microstructural characteristics of these systems. Further, mixed microemulsions at lower hydration levels produce synergistic performance compared to micelles and individual constituents in terms of reaction yield. These results reveal that the reaction occurs in neither the water nor oil domain, evidently in the micelle/water pseudo-phase and at the palisade layer of the oil/water interface of microemulsions. Moreover, reaction yields in the studied media are rationalized in terms of interaction parameters, spontaneity of micellization, interfacial population of 1-pentanol, and spontaneity of formation of w/o microemulsions.