Interactions of Proline in Non-aqueous Anionic, Cationic and Nonionic Surfactants at Different Temperatures

Density and viscosity data of proline (Pro) in sodium dodecyl sulfate/cetyltrimethylammonium bromide/poly (oxyethylene) isooctyl phenyl ether in formamide were measured at 298.15, 303.15, 308.15, and 313.15 K and 0.1 MPa. The density data were utilized to evaluate standard partial molar volumes ( ) and partial molar isobaric expansibility ( ). The viscosity data were used to evaluate A- and B-coefficients, free energy of activation of viscous flow ( ) and ( ), per mole of solvent and solute respectively, enthalpy (ΔH^*) and entropy (ΔS^*) of activation of viscous flow. The results obtained were utilized in the qualitative elucidation of the Pro-surfactant/formamide and Pro-Pro interactions in the present systems.     

Thermodynamic studies on the interactions of diglycine with magnesium chloride in aqueous medium at different temperatures

Apparent molar heat capacities (C_P2,?), apparent molar volumes (V_2,?), and viscosities (η) of diglycine in water and in aqueous magnesium chloride (MgCl₂) solutions of molality m_S ≈ (0.05 to 0.70) mol · kg⁻¹ over the temperature range T = (288.15 to 328.15) K have been determined using high sensitivity micro-differential scanning calorimeter, vibrating-tube digital density meter, and automatic viscosity measuring unit (AVS 350), respectively. The data have been used to calculate the partial molar heat capacities and partial molar volumes at infinite dilution. The viscosity B-coefficients have also been obtained from viscosity data using Jones-Dole equation. The and values of diglycine in aqueous MgCl₂ solutions are higher than those in water and thus exhibit positive transfer functions ( and ), which are indicative of strong interactions between diglycine and MgCl₂. Corresponding viscosity B-coefficients of transfer are also generally positive. The transfer functions decrease with increase in temperature and increase with the concentration of MgCl₂. The free energies, enthalpies and entropies of activation for viscous flow of diglycine in aqueous MgCl₂ solutions have been obtained by using the Feakins transition-state theory. Partial molar expansibilities and at infinite dilution along with their temperature dependence, the interaction coefficients from the volume, heat capacity, and viscosity B-coefficients have been used to divulge the various kinds of plausible interactions between solute (diglycine) and cosolute (MgCl₂) in solutions.