Effect of salt counterions on the physicochemical characteristics of novel green surfactant, ethane-1,2-diyl bis(N,N-dimethyl-N-tetradecylammoniumacetoxy) dichloride

Abstract

Abstract In this research article we have examined the effect of chloride (Cl−), sulphate (SO42−), phosphate (PO43−), anthranilate (An−) and tosylate (Tos−) counterions on the physicochemical characteristics of green gemini surfactant, ethane-1,2-diyl bis(N,N-dimethyl-N-tetradecylammoniumacetoxy) dichloride (14-E2-14) through a multidimensional approach. Substantial changes were observed in the physicochemical parameters. Counterions were found to cause reduction in critical micellar concentration (CMC) and minimum area per head group ( A min ) of the 14-E2-14 gemini surfactant. However, increase in aggregation number (Ng) and surface excess concentration ( Γ max ) of the 14-E2-14 surfactant was observed upon increasing the counterion concentrations. The Gibbs free energies of micellization (ΔG°mic) and adsorption (ΔG°ads) were found to be negative, indicating that 14-E2-14 micellization is spontaneous. The order of efficacy of counterions to influence the micellar characteristics was: An− > Tos− > PO43− > SO42− > Cl−. Further, 1H NMR results demonstrated morphological transitions (sphere-to-rod) and newer phase formation. The UV–vis and FT-IR results delineate intercalation of organic counterions (An− and Tos−) into the palisade layer of 14-E2-14 micelles. TEM micrographs show emergence of non-spheroidal micelles at higher counterion concentrations. This study could be significant to surfactant science scientists in tailoring green surfactants with desirable physicochemical characteristics, so that special-characteristic-tailored surfactants could be exploited in designing and compilation of environmentally benign industrial, cosmetic and biomedical products.