Bidyut Paul | Indian Statistical Institute, Calcutta (original) (raw)
Papers by Bidyut Paul
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2016
Abstract Mixtures of dissimilar surfactants can have superior properties compared to those of the... more Abstract Mixtures of dissimilar surfactants can have superior properties compared to those of the individual surfactant components involved, which provide impetus for research on interactions between surfactants. It was also demonstrated that a change in the composition of external phase promotes remarkable changes in interfacial properties of reverse micelles (RMs), which are crucial to understand the system in order to use them as nanoreactors. Hence, it should be achievable to explore the influence of non-ionic Tween-85 on the properties of anionic AOT based micelle as well as RMs in fatty acid esters [e.g., ethyl myristate (EM), ethyl palmitate (EP) and ethyl oleate (EO)]. A comprehensive micellization behavior is studied at different mixed compositions (XTween-85) by surface tension method. Non-ideal mixing behaviors along with synergistic interaction between the constituent surfactants in the mixed micelles are evidenced. Mixed micelles illustrate favorable micellization behavior in terms of thermodynamic parameters. Further, fatty acid ester medium-based mixed RM shows synergism in water solubilization capacity. Microstructures of these systems are investigated by conductance, DLS, and FTIR studies. The solvation and rotational relaxation dynamics using picosecond time-resolved emission spectroscopy (TRES) is used to investigate the effect of XTween-85 as well as chemical architecture of fatty acid esters for the first time on the excited state dynamics of fluorophore. The solvation dynamics is found to be faster with an increase in XTween-85 and the average solvation time follows the order, EO
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.
Indian journal of biochemistry & biophysics
The results of formation, phase behaviour and physical properties of biological microemulsions pr... more The results of formation, phase behaviour and physical properties of biological microemulsions prepared from saffola/AOT/hexylamine/water in presence of different additives, viz. cholesterol, crown ether, urea and brine, are presented. It has been found that the additives and temperature have striking effects; mono-, bi- and triphasic solutions interchanging proportions among themselves. The conduction of microemulsion at different [Water/AOT] ratios (w = 9,10,14,18,20,39 and 45) has shown conspicuous dependence on temperature with a significant degree of percolation, whereas the dependence of viscosity on temperature has shown normal declining trend with temperature. A maximum in viscosity with respect to its variation with amount of water has been observed. The Walden product (lambda eta) has evidenced noncompensation of ion transport by conduction with the viscosity of the medium. The activation energies evaluated for conduction (delta E*cond) and viscosity (delta E*vis) are syst...
Journal of Surfactants and Detergents, 2015
ABSTRACT Microemulsions are thermodynamically stable, isotropic transparent mixtures of two immis... more ABSTRACT Microemulsions are thermodynamically stable, isotropic transparent mixtures of two immiscible liquids (polar and nonpolar) and amphiphile(s) (usually surfactant and/or cosurfactant). The cosurfactant plays an important role by blending with surfactants, and partitioned between the coexisting aqueous and oleic phases to control the bending elasticity of the interfacial layer to render stability to the dispersion. The microheterogeneity of such disper- sions makes them useful in biological and technological applications. Various techniques viz. , conductance, inter- facial tension, SANS etc. were applied to estimate the distribution of cosurfactant between the interface and the bulk oil. However, a simple but ingenious method com- prising repetitively oil dilution with cosurfactant titration till attainment of stable microemulsions was also used to measure the distribution of cosurfactant. This review summarizes formation and characterization of water-in-oil microemulsions stabilized by single or mixed surfactants of different charge types and polar head groups or mixed surface active ionic liquid and surfactant, and cosurfactants of different lipophilicities in both hydrocarbons and long chain alkyl ester oil, emphasizing interfacial composition, thermodynamics of formation and structural parameters by the dilution method coupled with transport properties, microstructures and states of water organization inside the pool etc. using instrumental techniques. Applicability of the data obtained from dilution method in different areas, viz. nanomaterial synthesis, enzyme activity, etc. have been reported. Indeed, this article presented a journey of development and significant contribution in utilizing this elegant and inexpensive method to accomplish the forma- tion of microemulsion through consistent motivation by researchers of different countries.
RSC Advances, 2014
ABSTRACT The present report focuses on the evaluation of the interfacial composition and the ther... more ABSTRACT The present report focuses on the evaluation of the interfacial composition and the thermodynamics of transfer of 1-pentanol (Pn) from the continuous oil phase to the interface of w/o nonionic microemulsion [Tween-20/Pn/cyclohexane(Cy)/water] in absence and presence of an ionic liquid (IL) (1-butyl-3- propylbenzimidazolium bromide) under different physicochemical conditions [viz. variation in concentration of IL (0.0→0.20 mol dm-3) and temperature (293→323K] at a fixed molar ratio of water to surfactant (ω) by the Schulman’s method of cosurfactant titration at the oil/water interface. The overall transfer process has been found to be spontaneous, exothermic and organized in absence or presence of IL, but shown to be influenced by [IL]. The microstructure and state of water organization inside the pool of these systems have been characterized by different experimental techniques, e.g., conductivity, DLS and FTIR in absence or presence of IL. In addition, C-C cross coupling reaction (Heck reaction) has been employed to explore the properties of the IL (additive) in confined environment of the microemulsion vis-à-vis its interaction with the constituents of the interface. The progress of reaction has been monitored using above techniques. The reaction was ended up with the highest yield (75%) in presence of 0.05 mol dm-3 of IL, wherein the microemulsion forms spontaneously with highest stability.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2015
The Journal of Chemical Thermodynamics, 2013
ABSTRACT Temperature-induced percolation behavior in mixed reverse micellar systems (RMs) compris... more ABSTRACT Temperature-induced percolation behavior in mixed reverse micellar systems (RMs) comprising sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and polyoxyethylene(20) sorbitan trioleate (Tween-85) in polar lipophilic oils e.g., ethyl oleate (EO), isopropyl myristate (IPM) and isopropyl palmitate (IPP) was studied at a total surfactant concentration (ST) of 0.25 � 103 mol � m�3 in absence and presence of the additives (acetyl modified amino acids (MAA) of different chemical structures). The threshold temperature of percolation (Tp) of these systems was found to be dependent on water content (x), content of nonionic surfactant (XTween-85), and concentration of NaCl. The standard free energy change (DG0 cl), enthalpy change (DH0 cl) and entropy change (DS0 cl) of cluster formation were evaluated based on an association model at different physicochemical environments. The clustering process was spontaneous and found to be endothermic and entropically driven. Scaling laws for the temperature-induced percolation demonstrated dynamic nature of the percolation process. The activation energy, Ep of these systems was estimated both in absence and presence of additives. Droplet sizes of these systems were measured using dynamic light scattering (DLS) technique at different physicochemical environments (comparable to conductivity measurements) to underline the factors governed the percolation process. The chemical structure of the oils played an important role in influencing Tp, Ep, thermodynamic parameters and droplet size of these systems in absence and presence of the additives. An attempt has been made to underline the microstructures of these systems in the light of percolation of conductance vis-à-vis thermodynamics of droplet clustering and droplet dimensions.
Journal of Colloid and Interface Science, 2005
Journal of Colloid and Interface Science, 2007
The phase diagrams of the pseudo-quaternary systems poly(oxyethylene) (10) stearyl ether (Brij-76... more The phase diagrams of the pseudo-quaternary systems poly(oxyethylene) (10) stearyl ether (Brij-76)/1-butanol/isooctane/water (with equal amounts of oil and water in the presence of two nonaqueous polar solvents (NPS), ethylene glycol (EG), and tetraethylene glycol (TEG)), have been constructed at 30 degrees C. Regular fish-tail diagrams were obtained up to psi (weight fraction of EG or TEG in the mixture of polar solvents) equal to 0.5, confirming the establishment of hydrophile-lipophile balance (HLB) of the systems. The maximum solubilization capacity passed through a minimum at psi=0.2. No HLB was obtained at higher psi. The usual fish-tail diagrams were also obtained in temperature-induced phase mapping at fixed W(1) (weight fraction of 1-butanol in total amphiphile). Solubilization capacity and HLB temperature (T(HLB)) decreased with increasing psi at a fixed W(1), the effect being more pronounced for TEG than EG. A correlation between HLB temperature (T(HLB)) and HLB number (N(HLB)) of mixed amphiphiles (Brij-76+Bu) in pseudo-quaternary systems (in the presence of water and partial substitution of water with both NPS) has been established. The novelty of the work with respect to possible applications has been discussed.
Journal of Colloid and Interface Science, 2006
The conductivity of AOT/IPM/water reverse micellar systems as a function of temperature, has been... more The conductivity of AOT/IPM/water reverse micellar systems as a function of temperature, has been found to be non-percolating at three different concentrations (100, 175 and 250 mM), while the addition of nonionic surfactants [polyoxyethylene(10) cetyl ether (Brij-56) and polyoxyethylene(20) cetyl ether (Brij-58)] to these systems exhibits temperature-induced percolation in conductance in non-percolating AOT/isopropyl myristate (IPM)/water system at constant compositions (i.e., at fixed total surfactant concentration, omega and X(nonionic)). The influence of total surfactant concentration (micellar concentration) on the temperature-induced percolation behaviors of these systems has been investigated. The effect of Brij-58 is more pronounced than that of Brij-56 in inducing percolation. The threshold percolation temperature, Tp has been determined for these systems in presence of additives of different molecular structures, physical parameters and/or interfacial properties. The additives have shown both assisting and resisting effects on the percolation threshold. The additives, bile salt (sodium cholate), urea, formamide, cholesteryl acetate, cholesteryl benzoate, toluene, a triblock copolymer [(EO)13(PO)30(EO)13, Pluronic, PL64], polybutadiene, sucrose esters (sucrose dodecanoates, L-1695 and sucrose monostearate S-1670), formamide distinctively fall in the former category, whereas sodium chloride, cholesteryl palmitate, crown ether, ethylene glycol constitute the latter for both systems. Sucrose dodecanoates (L-595) had almost marginal effect on the process. The observed behavior of these additives on the percolation phenomenon has been explained in terms of critical packing parameter and/or other factors, which influence the texture of the interface and solution properties of the mixed reverse micellar systems. The activation energy, Ep for the percolation process has been evaluated. Ep values for the AOT/Brij-56 systems have been found to be lower than those of AOT/Brij-58 systems. The concentration of additives influence the parameters Tp and Ep for both systems. A preliminary report for the first time on the percolation phenomenon in mixed reverse micelles in presence of additives has been suggested on the basis of these parameters (Tp and Ep).
Journal of Colloid and Interface Science, 2002
Journal of Colloid and Interface Science, 2013
Journal of Colloid and Interface Science, 2005
The phase behavior of Brij-56/1-butanol/n-heptane/water is investigated at 30 degrees C with alph... more The phase behavior of Brij-56/1-butanol/n-heptane/water is investigated at 30 degrees C with alpha [weight fraction of oil in (oil+water)]=0.5, wherein a 2-->3-->2 phase transition occurs with increasing W1 (weight fraction of 1-butanol in total amphiphile) at low X (weight fraction of both the amphiphiles in the mixture) and a 2-->1-->2 phase transition occurs at higher X. Addition of an ionic surfactant, sodium dodecylbenzene sulfonate, destroys the three-phase body and decreases the solubilization capacity of the system at different delta (weight fraction of ionic surfactant in total surfactant). A three-phase body appears at alpha=0.25, but not at alpha=0.75 for the single system. No three-phase body appears with the mixed system at either alpha value. Increased temperature increases the solubilization capacity of the Brij-56 system; on the other hand, a negligible effect of temperature on the Brij-56/SDBS mixed system has been observed. Addition of salt (NaCl) produces a three-phase body for both single and mixed systems and increases their solubilization capacities. The monomeric solubility of 1-butanol in oil (S1) and at the interface (S1s) has been calculated using the equation hydrophile-lipophile balance plane for both singles- and mixed-surfactant systems. These parameters have been utilized to explain the increase in solubilization capacity of these systems in the presence of NaCl.
![Research paper thumbnail of Dilution Method Study on the Interfacial Composition, Thermodynamic Properties, and Structural Parameters of the [bmim][BF 4 ] + Brij-35 + 1-Butanol + Toluene Microemulsion](https://attachments.academia-assets.com/86116463/thumbnails/1.jpg)
](Journal of Chemical & Engineering Data, 2011
Journal of Chemical & Engineering Data, 2013
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
ABSTRACT In this report, phase behavior, conductivity, viscosity, dynamic light scattering, fluor... more ABSTRACT In this report, phase behavior, conductivity, viscosity, dynamic light scattering, fluorescence lifetime, steady state fluorescence anisotropy and Fourier transform infrared spectroscopy (FTIR) techniques were employed for understanding of the physicochemical properties and microenvironment of water-in-oil microemulsion comprising equimolar (1:1) cetyltrimethylammonium bromide (C(16)TAB) and polyoxyethylene (20) cetyl ether (C16E20)/1-butanol/heptane or decane, with varying water content (omega) at 303 K. Both conductivity and viscosity of these systems were increased with increase in omega in both oils. Droplet size was also increased with increase in omega and corroborated well with the conductance and viscosity measurements, and depends on oil chain length. The physicochemical changes in the microenvironment with increase in omega were presented by measuring the changes in decay time using a fluoroprobe (7-hydroxycoumarin). The effect of hydration on the microstructure of these systems was studied by polarized fluorescence measurements. FTIR measurements reveal three states of water molecules, viz. trapped, bound and bulk water, in water pool of these systems. Further, the interfacial composition and free energy of transfer of 1-butanol from oil to the interface were evaluated by the dilution method. Changes in interfacial composition as a function of omega corroborate well with FTIR results indicating bound and bulk water.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2013
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2013
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2005
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2016
Abstract Mixtures of dissimilar surfactants can have superior properties compared to those of the... more Abstract Mixtures of dissimilar surfactants can have superior properties compared to those of the individual surfactant components involved, which provide impetus for research on interactions between surfactants. It was also demonstrated that a change in the composition of external phase promotes remarkable changes in interfacial properties of reverse micelles (RMs), which are crucial to understand the system in order to use them as nanoreactors. Hence, it should be achievable to explore the influence of non-ionic Tween-85 on the properties of anionic AOT based micelle as well as RMs in fatty acid esters [e.g., ethyl myristate (EM), ethyl palmitate (EP) and ethyl oleate (EO)]. A comprehensive micellization behavior is studied at different mixed compositions (XTween-85) by surface tension method. Non-ideal mixing behaviors along with synergistic interaction between the constituent surfactants in the mixed micelles are evidenced. Mixed micelles illustrate favorable micellization behavior in terms of thermodynamic parameters. Further, fatty acid ester medium-based mixed RM shows synergism in water solubilization capacity. Microstructures of these systems are investigated by conductance, DLS, and FTIR studies. The solvation and rotational relaxation dynamics using picosecond time-resolved emission spectroscopy (TRES) is used to investigate the effect of XTween-85 as well as chemical architecture of fatty acid esters for the first time on the excited state dynamics of fluorophore. The solvation dynamics is found to be faster with an increase in XTween-85 and the average solvation time follows the order, EO
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.
Indian journal of biochemistry & biophysics
The results of formation, phase behaviour and physical properties of biological microemulsions pr... more The results of formation, phase behaviour and physical properties of biological microemulsions prepared from saffola/AOT/hexylamine/water in presence of different additives, viz. cholesterol, crown ether, urea and brine, are presented. It has been found that the additives and temperature have striking effects; mono-, bi- and triphasic solutions interchanging proportions among themselves. The conduction of microemulsion at different [Water/AOT] ratios (w = 9,10,14,18,20,39 and 45) has shown conspicuous dependence on temperature with a significant degree of percolation, whereas the dependence of viscosity on temperature has shown normal declining trend with temperature. A maximum in viscosity with respect to its variation with amount of water has been observed. The Walden product (lambda eta) has evidenced noncompensation of ion transport by conduction with the viscosity of the medium. The activation energies evaluated for conduction (delta E*cond) and viscosity (delta E*vis) are syst...
Journal of Surfactants and Detergents, 2015
ABSTRACT Microemulsions are thermodynamically stable, isotropic transparent mixtures of two immis... more ABSTRACT Microemulsions are thermodynamically stable, isotropic transparent mixtures of two immiscible liquids (polar and nonpolar) and amphiphile(s) (usually surfactant and/or cosurfactant). The cosurfactant plays an important role by blending with surfactants, and partitioned between the coexisting aqueous and oleic phases to control the bending elasticity of the interfacial layer to render stability to the dispersion. The microheterogeneity of such disper- sions makes them useful in biological and technological applications. Various techniques viz. , conductance, inter- facial tension, SANS etc. were applied to estimate the distribution of cosurfactant between the interface and the bulk oil. However, a simple but ingenious method com- prising repetitively oil dilution with cosurfactant titration till attainment of stable microemulsions was also used to measure the distribution of cosurfactant. This review summarizes formation and characterization of water-in-oil microemulsions stabilized by single or mixed surfactants of different charge types and polar head groups or mixed surface active ionic liquid and surfactant, and cosurfactants of different lipophilicities in both hydrocarbons and long chain alkyl ester oil, emphasizing interfacial composition, thermodynamics of formation and structural parameters by the dilution method coupled with transport properties, microstructures and states of water organization inside the pool etc. using instrumental techniques. Applicability of the data obtained from dilution method in different areas, viz. nanomaterial synthesis, enzyme activity, etc. have been reported. Indeed, this article presented a journey of development and significant contribution in utilizing this elegant and inexpensive method to accomplish the forma- tion of microemulsion through consistent motivation by researchers of different countries.
RSC Advances, 2014
ABSTRACT The present report focuses on the evaluation of the interfacial composition and the ther... more ABSTRACT The present report focuses on the evaluation of the interfacial composition and the thermodynamics of transfer of 1-pentanol (Pn) from the continuous oil phase to the interface of w/o nonionic microemulsion [Tween-20/Pn/cyclohexane(Cy)/water] in absence and presence of an ionic liquid (IL) (1-butyl-3- propylbenzimidazolium bromide) under different physicochemical conditions [viz. variation in concentration of IL (0.0→0.20 mol dm-3) and temperature (293→323K] at a fixed molar ratio of water to surfactant (ω) by the Schulman’s method of cosurfactant titration at the oil/water interface. The overall transfer process has been found to be spontaneous, exothermic and organized in absence or presence of IL, but shown to be influenced by [IL]. The microstructure and state of water organization inside the pool of these systems have been characterized by different experimental techniques, e.g., conductivity, DLS and FTIR in absence or presence of IL. In addition, C-C cross coupling reaction (Heck reaction) has been employed to explore the properties of the IL (additive) in confined environment of the microemulsion vis-à-vis its interaction with the constituents of the interface. The progress of reaction has been monitored using above techniques. The reaction was ended up with the highest yield (75%) in presence of 0.05 mol dm-3 of IL, wherein the microemulsion forms spontaneously with highest stability.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2015
The Journal of Chemical Thermodynamics, 2013
ABSTRACT Temperature-induced percolation behavior in mixed reverse micellar systems (RMs) compris... more ABSTRACT Temperature-induced percolation behavior in mixed reverse micellar systems (RMs) comprising sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and polyoxyethylene(20) sorbitan trioleate (Tween-85) in polar lipophilic oils e.g., ethyl oleate (EO), isopropyl myristate (IPM) and isopropyl palmitate (IPP) was studied at a total surfactant concentration (ST) of 0.25 � 103 mol � m�3 in absence and presence of the additives (acetyl modified amino acids (MAA) of different chemical structures). The threshold temperature of percolation (Tp) of these systems was found to be dependent on water content (x), content of nonionic surfactant (XTween-85), and concentration of NaCl. The standard free energy change (DG0 cl), enthalpy change (DH0 cl) and entropy change (DS0 cl) of cluster formation were evaluated based on an association model at different physicochemical environments. The clustering process was spontaneous and found to be endothermic and entropically driven. Scaling laws for the temperature-induced percolation demonstrated dynamic nature of the percolation process. The activation energy, Ep of these systems was estimated both in absence and presence of additives. Droplet sizes of these systems were measured using dynamic light scattering (DLS) technique at different physicochemical environments (comparable to conductivity measurements) to underline the factors governed the percolation process. The chemical structure of the oils played an important role in influencing Tp, Ep, thermodynamic parameters and droplet size of these systems in absence and presence of the additives. An attempt has been made to underline the microstructures of these systems in the light of percolation of conductance vis-à-vis thermodynamics of droplet clustering and droplet dimensions.
Journal of Colloid and Interface Science, 2005
Journal of Colloid and Interface Science, 2007
The phase diagrams of the pseudo-quaternary systems poly(oxyethylene) (10) stearyl ether (Brij-76... more The phase diagrams of the pseudo-quaternary systems poly(oxyethylene) (10) stearyl ether (Brij-76)/1-butanol/isooctane/water (with equal amounts of oil and water in the presence of two nonaqueous polar solvents (NPS), ethylene glycol (EG), and tetraethylene glycol (TEG)), have been constructed at 30 degrees C. Regular fish-tail diagrams were obtained up to psi (weight fraction of EG or TEG in the mixture of polar solvents) equal to 0.5, confirming the establishment of hydrophile-lipophile balance (HLB) of the systems. The maximum solubilization capacity passed through a minimum at psi=0.2. No HLB was obtained at higher psi. The usual fish-tail diagrams were also obtained in temperature-induced phase mapping at fixed W(1) (weight fraction of 1-butanol in total amphiphile). Solubilization capacity and HLB temperature (T(HLB)) decreased with increasing psi at a fixed W(1), the effect being more pronounced for TEG than EG. A correlation between HLB temperature (T(HLB)) and HLB number (N(HLB)) of mixed amphiphiles (Brij-76+Bu) in pseudo-quaternary systems (in the presence of water and partial substitution of water with both NPS) has been established. The novelty of the work with respect to possible applications has been discussed.
Journal of Colloid and Interface Science, 2006
The conductivity of AOT/IPM/water reverse micellar systems as a function of temperature, has been... more The conductivity of AOT/IPM/water reverse micellar systems as a function of temperature, has been found to be non-percolating at three different concentrations (100, 175 and 250 mM), while the addition of nonionic surfactants [polyoxyethylene(10) cetyl ether (Brij-56) and polyoxyethylene(20) cetyl ether (Brij-58)] to these systems exhibits temperature-induced percolation in conductance in non-percolating AOT/isopropyl myristate (IPM)/water system at constant compositions (i.e., at fixed total surfactant concentration, omega and X(nonionic)). The influence of total surfactant concentration (micellar concentration) on the temperature-induced percolation behaviors of these systems has been investigated. The effect of Brij-58 is more pronounced than that of Brij-56 in inducing percolation. The threshold percolation temperature, Tp has been determined for these systems in presence of additives of different molecular structures, physical parameters and/or interfacial properties. The additives have shown both assisting and resisting effects on the percolation threshold. The additives, bile salt (sodium cholate), urea, formamide, cholesteryl acetate, cholesteryl benzoate, toluene, a triblock copolymer [(EO)13(PO)30(EO)13, Pluronic, PL64], polybutadiene, sucrose esters (sucrose dodecanoates, L-1695 and sucrose monostearate S-1670), formamide distinctively fall in the former category, whereas sodium chloride, cholesteryl palmitate, crown ether, ethylene glycol constitute the latter for both systems. Sucrose dodecanoates (L-595) had almost marginal effect on the process. The observed behavior of these additives on the percolation phenomenon has been explained in terms of critical packing parameter and/or other factors, which influence the texture of the interface and solution properties of the mixed reverse micellar systems. The activation energy, Ep for the percolation process has been evaluated. Ep values for the AOT/Brij-56 systems have been found to be lower than those of AOT/Brij-58 systems. The concentration of additives influence the parameters Tp and Ep for both systems. A preliminary report for the first time on the percolation phenomenon in mixed reverse micelles in presence of additives has been suggested on the basis of these parameters (Tp and Ep).
Journal of Colloid and Interface Science, 2002
Journal of Colloid and Interface Science, 2013
Journal of Colloid and Interface Science, 2005
The phase behavior of Brij-56/1-butanol/n-heptane/water is investigated at 30 degrees C with alph... more The phase behavior of Brij-56/1-butanol/n-heptane/water is investigated at 30 degrees C with alpha [weight fraction of oil in (oil+water)]=0.5, wherein a 2-->3-->2 phase transition occurs with increasing W1 (weight fraction of 1-butanol in total amphiphile) at low X (weight fraction of both the amphiphiles in the mixture) and a 2-->1-->2 phase transition occurs at higher X. Addition of an ionic surfactant, sodium dodecylbenzene sulfonate, destroys the three-phase body and decreases the solubilization capacity of the system at different delta (weight fraction of ionic surfactant in total surfactant). A three-phase body appears at alpha=0.25, but not at alpha=0.75 for the single system. No three-phase body appears with the mixed system at either alpha value. Increased temperature increases the solubilization capacity of the Brij-56 system; on the other hand, a negligible effect of temperature on the Brij-56/SDBS mixed system has been observed. Addition of salt (NaCl) produces a three-phase body for both single and mixed systems and increases their solubilization capacities. The monomeric solubility of 1-butanol in oil (S1) and at the interface (S1s) has been calculated using the equation hydrophile-lipophile balance plane for both singles- and mixed-surfactant systems. These parameters have been utilized to explain the increase in solubilization capacity of these systems in the presence of NaCl.
Journal of Chemical & Engineering Data, 2011
Journal of Chemical & Engineering Data, 2013
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
ABSTRACT In this report, phase behavior, conductivity, viscosity, dynamic light scattering, fluor... more ABSTRACT In this report, phase behavior, conductivity, viscosity, dynamic light scattering, fluorescence lifetime, steady state fluorescence anisotropy and Fourier transform infrared spectroscopy (FTIR) techniques were employed for understanding of the physicochemical properties and microenvironment of water-in-oil microemulsion comprising equimolar (1:1) cetyltrimethylammonium bromide (C(16)TAB) and polyoxyethylene (20) cetyl ether (C16E20)/1-butanol/heptane or decane, with varying water content (omega) at 303 K. Both conductivity and viscosity of these systems were increased with increase in omega in both oils. Droplet size was also increased with increase in omega and corroborated well with the conductance and viscosity measurements, and depends on oil chain length. The physicochemical changes in the microenvironment with increase in omega were presented by measuring the changes in decay time using a fluoroprobe (7-hydroxycoumarin). The effect of hydration on the microstructure of these systems was studied by polarized fluorescence measurements. FTIR measurements reveal three states of water molecules, viz. trapped, bound and bulk water, in water pool of these systems. Further, the interfacial composition and free energy of transfer of 1-butanol from oil to the interface were evaluated by the dilution method. Changes in interfacial composition as a function of omega corroborate well with FTIR results indicating bound and bulk water.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2013
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2013
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2005