Temperature dependence of transport and equilibrium properties of alkylpyridinium surfactants in aqueous solutions

Conductivity measurements at varying concentrations and temperatures for two alkyl pyridinium surfactants-dodecylpyridinium chloride (DPC) and cetylpyridinium chloride (CPC) in aqueous medium have been performed. The resulting data in the lower concentration range were used for the determination of limiting transport parameters of the surfactant ions. Temperature dependence of limiting ion conductance λ+(surf.cation)∘ and limiting ion mobility u+(surf.cation)∘ of surfactant ions were used for determination of standard partial molar enthalpy of activation for ion migration (ΔHλ+∘#) and the change in activation energy for translational mobility (ΔEtrans∘) of water molecules from surfactant ion hydration shell. The conductivity data at higher concentrations were used for determination of equilibrium micellar parameters, viz. critical micelle concentration (cmc), degree of counter ion dissociation (α), and aggregation number (n). Comparison of such parameters of the two surfactants at different temperatures was made in the light of molecular structure, ion–solvent, ion–ion, and solvent–solvent interactions.