Temperature Dependence of Micellization Properties of Binary Mixtures of Sodium Decylsulphate with Sodium Dodecylsulphate in Water

Conductance measurement method has been used to determine the critical micelle concentration (CMC) and counterion binding constant values of binary mixtures of sodium decylsulphate (SDeS) with sodium dodecylsulphate (SDS) in water at four different temperatures ranging from 298 K to 313 K at 5 K intervals. Rubingh′s model has been used to calculate the mixed micellization properties viz. mixed micelle composition, activity coefficient of the components, and mutual interaction parameter between the components. Variation of these mixed micellization properties with temperature has been studied. The studied binary surfactant mixtures show attractive interaction between the components and it decreases with increase in temperature, which is an interesting trend. Thermodynamic parameters of mixed micellization have also been calculated. The enthalpy (ΔH°mic) and entropy (ΔS°mic) of micellization compensate each other.