Transition from antagonistic to synergistic interaction in mixed micellar system by increase in alkyl chain length of alkyl trimethylammonium bromide

Herein, the electrical conductivity technique used to measure the critical micelle concentration (cmc) for pure cationic surfactants (Dodecyl/cetyltrimethylammonium bromides) and phenothiazine drug (Promethazine hydrochloride), as well as their different mole fractions in 10^?3 ?mol/kg 1-methyl-3-octylimidazolium chloride (C₈mim.Cl) at different temperatures. By using the cmc values the regular solution theory used to evaluate the micellar mole fraction for DTAB/CTAB-PMT mixed systems. The clint's model used to calculate the ideal critical micelle concentration (cmc1) that helps to evaluate the ideal micellar mole fraction for studied mixed systems, both explain the deviation from ideality. In addition, interaction parameter β^m helps to confirm the nature of interaction (either antagonistic or synergistic) for the studied systems. The calculated parameters confirm a transition in the binding nature from antagonistic to synergistic with the increase in alkyl chain length of cationic surfactant i.e., component of the binary mixed system. The ease of micellization for the studied systems discussed by the standard Gibb's energy of micellization ($\Delta G_m^0$), as well as the standard enthalpy and standard entropy of micellization were ($\Delta H_m^0$) and ($\Delta S_m^0$), respectively to discuss the stability of the studied systems.     

Volumetric and acoustic studies of aqueous l-arginine·HCl and l-proline in electrolytic and non-electrolytic solutions at various temperatures

Densities and speed of sound of l-arginine hydrochloride and l-proline within the concentration range (0.03–0.2) mol.kg^?1 in water and in aqueous NaCl and Urea are determined between temperatures 288.15 K and 318.15 K and at one atmospheric pressure. Densities and speeds of sound have been used to calculate apparent molar volume of solute ($V_{\phi }$), isentropic compressibility of solution (${\kappa }_S$), apparent molar isentropic compressibility ($K_{S,\phi }$) of solute, limiting apparent molar volume ($V_{\phi }^0$), limiting apparent molar volume of transfer (${\Delta }_{tr}{V}_{\phi }^0$), limiting apparent molar expansibility ($E_{\phi }^0$), limiting apparent molar isentropic compressibility ($K_{S,\phi }^0$) and limiting apparent molar isentropic compressibility of transfer (${\Delta }_{tr}{K}_{S,\phi }^0$). These results are then interpreted in terms of intermolecular interactions. The concentration dependencies of the calculated quantities, their limiting values and temperature characteristics are discussed in terms of solute - solvent and solute - solute interactions at experimental conditions.