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V K Aswal - One of the best experts on this subject based on the ideXlab platform.
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effect of alkyl chain length and head group on surface active and aggregation behavior of ionic liquids in water
Fluid Phase Equilibria, 2012Co-Authors: N V Sastry, Nilesh M Vaghela, V K AswalAbstract:Abstract A series of Surfactant-like ionic liquids (ILs), typically consisting of a long hydrocarbon tail and an ionic head group have been synthesized by a direct reaction of 1-methylimidazole and 1-choloroalkane, RCl, R = C 10 , C 12 , C 14 , C 16 and C 18 , 1-methylpipridine or 1-methylpyrrolidine and 1-chlorooctadecane respectively. Surface activity and aggregation of these Surfactants have been explored by surface tension and solution conductivity measurements. New results (critical aggregation concentrations (cac), and surface active parameters (at 298.15 K), thermodynamic parameters of aggregation (at 298.15, 303.15 and 313.15 K)) are reported. The increase in length of R decreased cac, minimum area/Surfactant Molecule at air/water interface and while the adsorption efficiency, surface excess concentrations, standard entropy of aggregation were increased indicating that the aggregation with in the temperature limits of present study is an entropy driven process. The analysis of the small angle neutron scattering (SANS) curves revealed that the aggregates are of oblate ellipsoidal shape and the aggregation numbers increased with the increase in the chain length (C 10 –C 18 ) of alkyl branch and therefore it is suggested that the longer the alkyl chains, parallel would be their alignment in the core part of the aggregates. Comparison of surface active parameters for the three ILs with a common octadecyl chain but different cationic head groups revealed that the methylimidazolium moiety is more effective than methylpiperidine and methylpyrrolidine at air/water interface. Similarly, the number of Molecules in an aggregate was found to be more, when the cationic head group is made up of π electron ring systems as compared to the one with point charge.
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role of counterion of the Surfactant Molecule on the micellar structure in aqueous solution
Current Science, 2002Co-Authors: J V Joshi, V K Aswal, Pratap Bahadur, P S GoyalAbstract:This article reports the sizes and shapes of micelles of anionic Surfactants of LiDS, NaDS, KDS, RbDS and CsDS in aqueous solutions as studied by the technique of small-angle neutron scattering. The micelles of these Surfactants are made up of negatively charged DS - ions, while the positively charged ions such as Na + (referred to as counterions) tend to stay near the micellar surface. The present study shows that the distribution of counterions around the micelle depends on hydrophilicity of the counterions, and this in turn decides the micellar structure.
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micellar structure and inter micelle interactions in micellar solutions results of small angle neutron scattering studies
2001Co-Authors: P S Goyal, V K AswalAbstract:Micelles are aggregates of Surfactant Molecules suspended in water. The structure (shape and size) of a micelle depends both on the architecture of the constituent Surfactant Molecule and the solution conditions such as temperature, presence of impur ities, etc. The inter-particle interaction between micelles also depends on several different parameters. It is of interest to study the structure and intermicellar interactions in micellar solutions both from the point of view of basic research and the applic ations. It has been found that the technique of Small Angle Neutron Scattering (SANS) is ideally suited for the above studies. This paper gives an introdu ction to the technique of SANS and discusses the results of typical SANS studies dealing with the mice llar structure and the inter-micellar interactions.
Dinesh O Shah - One of the best experts on this subject based on the ideXlab platform.
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adsorption of nonionic brij and tween Surfactants at ptfe water and air water interfaces investigations on wetting dispersion stability foaming and drug solubilization
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2016Co-Authors: Vidhi Shah, Bhavesh Bharatiya, Atindra D Shukla, Tulsi Mukherjee, Dinesh O ShahAbstract:Abstract Aqueous solutions of nonionic Surfactants, namely Brij O10, Brij 35, Brij 98, Tween 20, Tween 60 and Tween 80 are investigated to understand their diffusion from the bulk solution to the surface and adsorption processes at PTFE-water interface using dynamic surface tension (DST), water penetration in packed PTFE powder and rate of sedimentation measurements. DST correlates well with the water penetration in packed PTFE powder (wettability) and the rate of sedimentation in aqueous dispersions for Brij Surfactants. The results are described in terms of the structural features and HLB of respective Surfactant and its ability to diffuse and adsorb at the interface. Brij O10 and Tween 60 showed maximum wettability and dispersion stability for respective series. We correlate the dynamic surface tension with interfacial phenomenon e.g. water penetration in the packed PTFE powder and the rate of sedimentation for aqueous dispersions. The diffusion towards air-water interface was essentially controlled by the molecular weight of the Surfactant, while adsorption on the hydrophobic PTFE is controlled by the HLB of the respective Surfactant Molecule. We introduce a strategy to use PTFE particles as model for aqueous formulations involving hydrophobic drugs. The water penetration, wettability and stability of PTFE dispersions increase with lower DST values.
Sowhsin Chen - One of the best experts on this subject based on the ideXlab platform.
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a small angle neutron scattering study of nonionic Surfactant Molecules at the water oil interface area per Molecule microemulsion domain size and rigidity
Journal of Chemical Physics, 1997Co-Authors: Thomas Sottmann, R Strey, Sowhsin ChenAbstract:The small-angle neutron scattering (SANS) of bicontinuous microemulsions of 19 different water-n-alkane-CiEj (n-alkylpolyglycolether) systems has been measured. All scattering curves exhibit a broad scattering peak which permits determining the characteristic length scale ξ for bicontinuous structures at symmetric water and oil volume fractions, i.e., φ=0.5. Various random models predict ξ=aδφ(1−φ)/φc. We find that ξ is indeed inversely proportional to the Surfactant volume fraction φc. Approximating the effective Surfactant chain length δ by δ=νc/ac, where ac and νc are the area and the volume of the Surfactant Molecule, the numerical value for a is determined to be a=7.16, which is close to, but significantly different from those used in theoretical models. The head group area ac at the water–oil interface is obtained from the large q part of the scattering curves. It is found to be independent of i and k, the carbon numbers of the alkyl chain of the Surfactant and of the alkane, respectively. However, ...
Thomas Sottmann - One of the best experts on this subject based on the ideXlab platform.
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a small angle neutron scattering study of nonionic Surfactant Molecules at the water oil interface area per Molecule microemulsion domain size and rigidity
Journal of Chemical Physics, 1997Co-Authors: Thomas Sottmann, R Strey, Sowhsin ChenAbstract:The small-angle neutron scattering (SANS) of bicontinuous microemulsions of 19 different water-n-alkane-CiEj (n-alkylpolyglycolether) systems has been measured. All scattering curves exhibit a broad scattering peak which permits determining the characteristic length scale ξ for bicontinuous structures at symmetric water and oil volume fractions, i.e., φ=0.5. Various random models predict ξ=aδφ(1−φ)/φc. We find that ξ is indeed inversely proportional to the Surfactant volume fraction φc. Approximating the effective Surfactant chain length δ by δ=νc/ac, where ac and νc are the area and the volume of the Surfactant Molecule, the numerical value for a is determined to be a=7.16, which is close to, but significantly different from those used in theoretical models. The head group area ac at the water–oil interface is obtained from the large q part of the scattering curves. It is found to be independent of i and k, the carbon numbers of the alkyl chain of the Surfactant and of the alkane, respectively. However, ...
Antonio Vincitore - One of the best experts on this subject based on the ideXlab platform.
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surface tension model for Surfactant solutions at the critical micelle concentration
Journal of Colloid and Interface Science, 2013Co-Authors: Sergei F. Burlatsky, Vadim V. Atrazhev, Vadim I Sultanov, Elena Timokhina, Elena A Ugolkova, D. V. Dmitriev, Sonia Tulyani, Antonio VincitoreAbstract:A model for the limiting surface tension of Surfactant solutions (surface tension at and above the critical micelle concentration, cmc) was developed. This model takes advantage of the equilibrium between the Surfactant Molecules on the liquid/vacuum surface and in micelles in the bulk at the cmc. An approximate analytical equation for the surface tension at the cmc was obtained. The derived equation contains two parameters, which characterize the intermolecular interactions in the micelles, and the third parameter, which is the surface area per Surfactant Molecule at the interface. These parameters were calculated using a new atomistic modeling approach. The performed calculations of the limiting surface tension for four simple Surfactants show good agreement with experimental data (∼30% accuracy). The developed model provides the guidance for design of Surfactants with low surface tension values.