Influence of 1,4-dioxane on the aggregation of bis(tetradecyldimethylammonium)butane dibromide gemini surfactant

Abstract

The aggregation behavior of bis(tetradecyldimethylammonium)butane dibromide (14-4-14, 2Br-) gemini surfactant in various compositions of 1,4-dioxane–water (DO–WR) mixed media across a range of temperatures has been investigated by means of electrical conductivity and steady state fluorescence quenching measurements. The parameters determined and discussed include critical micelle concentration (cmc), degree of counter ion dissociation (α), average aggregation number (Nagg) and micropolarity (I1/I3). The thermodynamic parameters of micellization were computed from the temperature dependence of the cmc. At a fixed temperature, adding DO to the solvent medium causes an increase in cmc, an initial declination and further increase in α and a regular decrease in Nagg. The micropolarity of the medium around the pyrene in the presence of 14-4-14, 2Br− micelles remains almost the same up to 20% DO and shows increase in 30 and 40% DO media while in the absence of 14-4-14, 2Br− a regular decrease was obtained. Thermodynamic analysis shows that, although micellization is less favored in DO–WR mixed media than in water, the process is spontaneous and exothermic. Compensation of enthalpy and entropy of micellization of 14-4-14, 2Br− is observed in the DO–WR mixed media.