Interfacial properties and micellization of octadecyltrimethylammonium bromide in aqueous solution containing short chain alcohol and effect of chain length of alcohol

Abstract

The interfacial behavior and the process of micellization of octadecyltrimethylammonium bromide (OTAB) in aqueous solution without or with 70 g/L short chain alcohol including methanol, ethanol, 1-propanol and 1-butanol were investigated by both the tensiometry and the conductometry at 313.15 K. Based on the data of tension and conductivity, the maximum adsorption (Γmax) at the air-liquid interface, the minimum area per molecule (ASmin) at the saturated interface, the critical micelle concentration (cmc), the degree of ionization (α) at the surface of micelle, the packing parameter (P) and the standard free energy change of micellization (ΔG0mic) were obtained. The presence of alcohol and the change of the chain length of alcohol alter the hydrophobic effect, the electrostatic interaction and the presence of alcohol molecule at the air-liquid interface or in the micelle, causing the variation in the interfacial or micellization behavior. The data of ΔG0mic also confirm the process of micellization. These findings help with understanding the molecular interaction between surfactant and alcohol and further obtain some information about the contribution of cosolvent on the surfactant formulation.