Micellar properties of selected benzalkonium surfactants by calorimetric analysis

•The microcalorimetry measurements of aqueous benzalkonium surfactants solutions in the (278.15 – 333.15) K temperature range.•Modified Sigmoidal Equation allowed to determine the critical micelle concentration.•The influence of temperature on the critical concentration of micellization was analyzed.•The thermodynamic parameters of the micellization process in the studied systems were analyzed.•Enthalpy-entropy compensation was discussed. This paper presents the results of calorimetric research and thermodynamic analysis of aqueous solutions of cationic surfactants: dodecylbenzyldimethylammonium bromide (C12BDABr) and tetradecylbenzyldimethylammonium chloride (C14BDACl) in a wide range of temperature from (278.15 to 333.15) K. The modified Sigmoidal Boltzman Equation (SBE) allowed us to determine the values of the critical micelle (c.m.c.) concentration with high precision. In order to obtain the results of studies of the selected systems, the measurements were carried out using the isothermal calorimetric titration (ITC) method. Furthermore, the influence of temperature on the critical concentration of micellization was analyzed. Calorimetric measurements made it possible to present, for the first time, the experimentally obtained values of the enthalpy of micellization in a wide temperature range for the tested systems. Moreover, the other thermodynamic parameters of the micellization process (enthalpy, entropy, and Gibbs energy) in the studied systems were analyzed, as well as we pointed at the enthalpy–entropy compensation.