The thermodynamics of micelle formation of the cationic surfactants decyltrimethylammonium chloride (DeTAC) and tetradecyltrimethylammonium chloride (TTAC) in water and aqueous NaCl solutions have been investigated. Isothermal titration calorimetry (ITC) was used to study the effect of added salt on the critical micelle concentration, cmc, and enthalpy of micellization, Delta H-mic(o), between the temperatures (278.15 and 328.15) K. From the temperature dependence of Delta H-mic(o), the heat capacities of micellization, Delta(mic)c(p)(o) were determined. The results obtained are compared with reported data for dodecyltrimethylammonium chloride (DTAC). The values of Delta(mic)c(p)(o) are negative for all surfactants in all solvents relating to the removal of water accessible non-polar surfaces also in the presence of excess counterions. The temperature dependence of Delta(mic)c(p)(o) is evident at DeTAC, leading to the assumption that, especially at high temperatures, the nonpolar parts of surfactant molecules are still in perceivable contact with water. (C) 2011 Elsevier Ltd. All rights reserved.