Temperature Dependant Micellization of AOT in Aqueous Medium: Effect of the Nature of Counterions

The lithium, potassium, and ammonium salts of bis (2‐ethylhexyl) sulphosuccinic acid have been prepared from the sodium salt (AOT) by applying ion‐exchange technique. The critical micellization concentrations (cmc) of the surfactants with four different counterions have been determined at a temperature range of 10°C to 40°C using surface tension as well as electrical conductivity measurements. Observed data have been utilized to evaluate the ionization degree (counter ion association constant),α, and various thermodynamic parameters of micellization viz, free energy, enthalpy, entropy changes of micelle formation, and also the surface parameters (Γmax, Amin) in aqueous media. The value of cmc decreases with hydrated ionic size of the counter ions (except K+) and follows the order NH4 +>Na+>Li+>K+. While large negative free energy change (ΔG0 m) and the positive entropy change (ΔS0 m) favor the micellization process thermodynamically, nature of their variation with counterion supports the involvement of counterion size factor in micellization process via a change in the hydrophilicity of surfactant head group.

[1]  R. Zana,et al.  Effect of the Nature of the Counterion on the Properties of Anionic Surfactants. 1. Cmc, Ionization Degree at the Cmc and Aggregation Number of Micelles of Sodium, Cesium, Tetramethylammonium, Tetraethylammonium, Tetrapropylammonium, and Tetrabutylammonium Dodecyl Sulfates , 2003 .

[2]  A. Blume,et al.  Thermodynamic Characterization of Temperature-Induced Micellization and Demicellization of Detergents Studied by Differential Scanning Calorimetry , 2001 .

[3]  B. Jha,et al.  Effect of Antifoaming Agents on the Micellar Stability and Foamability of Sodium Dodecyl Sulfate Solutions , 1999 .

[4]  H. Hurwitz,et al.  Fourier Transform Infrared Investigation of Water States in Aerosol-OT Reverse Micelles as a Function of Counterionic Nature , 1998 .

[5]  G. Onori,et al.  Calorimetric Study of the Micellization of n-Butoxyethanol in Water , 1997 .

[6]  A. Blume,et al.  Thermodynamics of Micelle Formation as a Function of Temperature: A High Sensitivity Titration Calorimetry Study , 1995 .

[7]  B. Lee,et al.  Enthalpy-entropy compensation in the thermodynamics of hydrophobicity. , 1994, Biophysical chemistry.

[8]  B. Lee,et al.  Role of hydrogen bonds in hydrophobicity: the free energy of cavity formation in water models with and without the hydrogen bonds. , 1994, Biophysical chemistry.

[9]  J. Rosenholm,et al.  Enthalpies of mixing a non-ionic surfactant with water at 303.15 K studied by calorimetry , 1994 .

[10]  R. Heenan,et al.  Water-in-oil microemulsions formed by ammonium and tetrapropylammonium salts of aerosol-OT , 1993 .

[11]  D. Shah,et al.  Effect of Counterions on the Interfacial Tension and Emulsion Droplet Size in the Oil/Water/ Dodecyl Sulfate System , 1993 .

[12]  J. Engberts,et al.  Toward a better understanding of the driving force for micelle formation and micellar growth , 1992 .

[13]  E. Franses,et al.  Estimation of micellization parameters of aqueous sodium dodecyl sulfate from conductivity data , 1992 .

[14]  Y. Moroi.  Micelles: Theoretical and Applied Aspects , 1992 .

[15]  H. Rehage,et al.  Viscoelastic surfactant solutions: model systems for rheological research , 1991 .

[16]  B. Lee,et al.  Solvent reorganization contribution to the transfer thermodynamics of small nonpolar molecules , 1991, Biopolymers.

[17]  H. Hoffmann,et al.  Shear Induced Micellar Structures , 1991 .

[18]  G. Haandrikman,et al.  The effect of chemical structure upon the thermodynamics of micellization of model alkylarenesulfonates: III. Determination of the critical micelle concentration and the enthalpy of demicellization by means of microcalorimetry and a comparison with the phase separation model , 1991 .

[19]  T. Takagi,et al.  Micellar properties of octylglucoside in aqueous solutions , 1990 .

[20]  C. Mesa.  Dependence of critical micelle concentrations on intensive variables: a reduced variables analysis , 1990 .

[21]  P. Privalov,et al.  The hydrophobic effect: a reappraisal , 1989 .

[22]  D. Myers.  Surfactant Science and Technology , 1988 .

[23]  Barry W. Ninham,et al.  Molecular forces in the self-organization of amphiphiles , 1986 .

[24]  M. Nakagaki,et al.  Effect of structure on activity at the critical micelle concentration and on the free energy of micelle formation. Ionic and nonionic surfactants , 1984 .

[25]  Barry W. Ninham,et al.  Ion binding and the hydrophobic effect , 1983 .

[26]  K. Birdi.  Calorimetric determination of the enthalpy of micelle formation in aqueous media , 1983 .

[27]  M. J. Rosen,et al.  Relationship of structure to properties in surfactants. 10. Surface and thermodynamic properties of 2-dodecyloxypoly(ethenoxyethanol)s, C12H25(OC2H4)xOH, in aqueous solution , 1982 .

[28]  Dinesh O. Shah,et al.  Surface Phenomena in Enhanced Oil Recovery , 1981 .

[29]  C. H. Walker.  The Hydrophobic Effect: Formation of Micelles and Biological Membranes , 1981 .

[30]  J. D. Bene.  AN AB INITIO MOLECULAR ORBITAL STUDY OF 2‐ AND 4‐MONOSUBSTITUTED PYRIDINES , 1980 .

[31]  J. D. Bene.  An ab initio molecular orbital study of 2- and 4-monosubstituted pyridines , 1979 .

[32]  H. Hoffmann,et al.  Chemical relaxation and equilibrium studies of aqueous solutions of laurylsulfate micelles in the presence of divalent metal ions , 1978 .

[33]  J. Ferreira,et al.  A microcalorimetric method of determination of critical micellar concentration and enthalpy of micellization , 1976 .

[34]  E. W. Anacker.  The hydrophobic effect: Formation of micelles and biological membranes , 1975 .

[35]  C. Jolicoeur,et al.  Enthalpy–Entropy Compensation for Micellization and Other Hydrophobic Interactions in Aqueous Solutions , 1974 .

[36]  M. J. Rosen.  The relationship of structure to properties in surfactants , 1972 .

[37]  B. W. Barry,et al.  Prediction of the micellar molecular weight and thermodynamics of micellization of mixtures of alkyltrimethylammonium salts. , 1972, The Journal of pharmacy and pharmacology.

[38]  R. Lumry,et al.  Enthalpy–entropy compensation phenomena in water solutions of proteins and small molecules: A ubiquitous properly of water , 1970, Biopolymers.

[39]  A. Holtzer,et al.  The hydrophobic bond in micellar systems. Effects of various additives on the stability of micelles of sodium dodecyl sulfate and of n-dodecyltrimethylammonium bromide. , 1967, Journal of Physical Chemistry A.

[40]  P. Mukerjee.  The nature of the association equilibria and hydrophobic bonding in aqueous solutions of association colloids , 1967 .

[41]  I. Satake,et al.  The Surface Activities of Bivalent Metal Alkyl Sulfates. I. On the Micelles of Some Metal Alkyl Sulfates , 1963 .

[42]  G. C. Benson,et al.  CONDUCTIVITY OF AQUEOUS SOLUTIONS OF SOME PARAFFIN CHAIN SALTS , 1957 .