Investigation of the effect of temperature and electrolytes on the physicochemical parameters for the self-assembly of dodecyltrimethylammonium bromide

Abstract

In this work, we investigated the impact of different electrolytes (NaBr, Na₂SO₄, and Na₃PO₄) and temperatures on the aggregation behavior of dodecyltrimethylammonium bromide (DTAB) through the conductivity measurement technique. The measurements were conducted at a single fixed temperature (310.55 K) for different concentrations of electrolytes and a range of temperatures (300.55–320.55) K with a 5 K interval for one chosen concentration of all electrolytes. The critical micelle concentration (CMC) values decreased in attendance of salts as well but were found higher with the enhancement of temperature. In attendance of salts, the CMC values of DTAB at 310.55 K and ionic strength (I) of 1 mmol kg⁻¹ followed the order: ${c}_{\mathrm{NaBr}}> {c}_{{\mathrm{Na}}_{2}{\mathrm{SO}}_{4}}>{c}_{{\mathrm{Na}}_{3}{\mathrm{PO}}_{4}}$. The ∆G⁰_m values were found negative for DTAB aggregation in electrolytes solutions which indicates that the micellization process was spontaneous in nature. For DTAB in electrolytes media, the micellization processes is both enthalpy and entropy dominated which is revealed by the values of ${\Delta H}_{\mathrm{m}}^{0}$ & ∆S⁰_m. The enthalpy–entropy compensation was determined from the linear relationship between ∆H⁰_m and ∆S⁰_m values in every circumstance. The compensation temperature and intrinsic enthalpy gain were determined and illustrated.