The influence of counter-ions (acetate and benzoate) on the properties of alkyl triethanolammonium cationic surfactants

Quaternary ammonium salts were synthesized from alkyl bromides (C₈–C₁₄) and triethanolamine. The resulting alkyltriethanolammonium bromide salts were then converted into quaternary ammonium salts containing organic anions by replacing the bromide counterion with acetate and benzoate. Depending on the nature of the counterion (acetate and benzoate), the surface activity parameters of these quaternary ammonium cationic surfactants (including surface pressure, excess adsorption, surface area occupied by the polar group, efficiency, and degree of counterion binding) were determined using surface tension and specific electrical conductivity measurements. The ability of the quaternary ammonium salts to disperse thin oil films on the water surface was investigated as a function of both the counterion's nature and the alkyl chain length. The antimicrobial properties of the synthesized quaternary ammonium salts were evaluated against Gram-positive and Gram-negative bacteria, as well as Candida fungus. Additionally, the foaming capacity and foam stability of the surfactants were investigated in relation to the counterion's nature and the alkyl chain length.