Investigation of the impacts of temperature and electrolyte on the interaction of cationic surfactant with promethazine hydrochloride: Combined conductivity and molecular dynamics studies

Abstract Promethazine hydrochloride (PMH) is used to treat nausea, vomiting related diseases, allergic reactions, etc. Herein, by applying conductivity measurement technique, interaction between PMH drug and tetradecyltrimethylammonium bromide (TTAB) was determined in presence of sodium salts (NaCl, Na2SO4) having different concentrations at a fixed temperature (310.55 K) and a fixed salt concentration at different temperatures (300.55–320.55 K) with an interval of the temperature of 5.0 K. The single critical micelle concentration (CMC) for mixture of both components in attendance of salts was observed. In the occurrence of different salts (NaCl, Na2SO4) the CMC values were found to decrease in magnitude compared to those in water and thus electrolytes create a favorable environment for early micelle formation of PMH + TTAB. The obtained negative ΔG0m values imply the spontaneity of the micellization phenomena. Various physico-chemical indicators including Gibbs free energy change (ΔG0m), enthalpy change (ΔH0m), entropy change (ΔS0m), molar heat capacity (ΔC0m), etc. were evaluated and demonstrated clearly. The intrinsic enthalpy gain (ΔH0,⁎m), as well as the compensation temperature (Tc), were also determined and explained carefully. Molecular dynamics simulation technique was employed to unveil the mechanism of drug-surfactant interactions present at the atomic level, which revealed the fine treaty with the experimental outcomes.