A novel cationic Gemini surfactant with amide group: synthesis and micellization behavior in aqueous solutions

Abstract

Novel cationic Gemini surfactant with amide group, N 1,N 10-bis(3-dodecanamidopropyl)-N 1,N 1,N 10,N 10-tetramethyldecan-1,10-diammonium bromide (abbreviated as 2C12enAm) has been synthesized by two-step reactions, purified and characterized in our laboratory. The critical micelle concentration (CMC) values of this Gemini surfactant were determined using electrical conductivity and surface tension measurements in the range of temperatures from 298.15 to 328.15 K. It was observed that the CMC value of Gemini surfactant has a much lower value compared with monomeric ones and shows a slight increase with an increase in the temperature. The interactions between Gemini and conventional monomeric surfactant hexadecyltrimethylammonium bromide (CTAB) have been studied using the conductivity at a certain micellar concentration and temperature range. Rubingh’s theory is used to evaluate the micellar interaction parameters (β) for the mixed systems. It has been observed that mixed micelle formation in all the binary mixtures exhibited negative synergism (antagonism) or ideal behavior due to positive β values. Thermodynamics parameters were also obtained from the temperature dependence of the CMC values. From the surface tension measurements, CMC, maximum surface excess concentration at the solution/air interface (Γmax), minimum area per surfactant molecule (A min), the surface pressure at CMC (ΠCMC), the surfactant concentration required to reduce the surface tension of solvent by 20 mN m−1 (pC20), and thermodynamic parameters have been evaluated at same temperatures.