Study of Intermolecular Interactions of CTAB with Amino Acids at Different Temperatures: A Multi Technique Approach

The densities, rho, viscosities, eta and specific conductivities kappa, of (0.0002, 0.0004, 0.0006 and 0.0008 m) CTAB in 0.1 m aqueous valine, leucine and isoleucine were measured at different temperatures. The measured data were used to calculate various useful thermodynamic parameters. A complete characterization of any mixture can be performed by means of these thermo-dynamic properties. The apparent molar volume, phi(v), partial molar volume, phi(0)(v) and partial molar isobaric expansibilities, phi(0)(E), were calculated using density data. The viscosity data were analyzed using Jones-Dole equation to obtain viscosity coefficients, A- and B-, free energy of activation per mole of solvent, Delta mu(1)degrees* , and solute, Delta mu(2)degrees*, enthalpy, Delta H* and entropy, Delta S* of activation of viscous flow. Measuring the changes in these properties has been found to be an excellent qualitative and quantitative way to obtain information regarding the molecular structure and intermolecular interactions occurring in these mixtures. Various structure-making/breaking ability of solute (cetyltrimethylammonium bromide) in presence of aqueous amino acid solutions were discussed. In addition, fluorescence study using pyrene as a photophysical probe has been carried out, the results of which support the conclusions obtained from other techniques.