Micellar behavior of dodecyldimethylethyl ammonium bromide and dodecyltrimethylammonium chloride in aqueous media in the presence of diclofenac sodium

The micellar properties of cationic surfactants (S) viz. dodecyldimethylethyl ammonium bromide (DDAB) and dodecyltrimethylammonium chloride (DTAC) in aqueous media in the presence of diclofenac sodium (D) have been investigated by spectroscopic and conductivity measurements. The UV–vis and 1H NMR studies suggest possible packing of diclofenac sodium molecules in the micelles. The conductivity studies were carried out over the temperature range 288.15–308.15 K. The critical micelle concentration (cmc) and degree of counterion binding (β) of the micelles were determined at different temperatures. Delay in micellisation was observed for both DDAB and DTAC. Thermodynamic parameters ( Δ G m 0 , Δ H m 0 and Δ S m 0 ) for the micelle system were estimated by applying the charged pseudo-phase separation model. The results of the ternary S/D/W system were analysed in comparison with the reported results of binary S/W system. The Δ G m 0 values for the ternary S/D/W system in both the cases show an increase in comparison to the respective binary S/W system. However, Δ S m 0 decreased with temperature and remained positive in both the systems. At lower temperatures, the micellisation was found to be entropy-driven while at higher temperatures it was enthalpy-driven.