Synthesis and investigation of surface activity of amino acid surfactants
Abstract
The objective of this research is to systematically examine the influence of structural modifications of hexadecyltrimethylammonium bromide (HDTMAB) and dihexadecyldimethylammonium bromide (DHDAB) through the introduction of 4-aminobenzoic acid, resulting in the formation of new compounds—HDTMAK and DHDAK, respectively. The study evaluates how the incorporation of polar functional groups affects the physicochemical properties of surfactants, including critical micelle concentration (CMC), surface tension, foam-forming ability, foam stability, as well as emulsifying properties. The findings indicate that the modified surfactants HDTMAK and DHDAK exhibit lower CMC and surface tension compared to the original HDTMAB and DHDAB, suggesting higher surface activity and micelle-forming capability. Additionally, it is revealed that HDTMAK and DHDAK demonstrate enhanced foam-forming ability and foam stability, rendering them more suitable for applications requiring prolonged and resilient foams. Modification of molecules leads not only to enhanced emulsifying capability but also to changes in the stabilization mechanism: the introduction of amino acid increases hydrophilicity, enhances adsorption saturation at the water/oil interface, and forms a dense interfacial film with high strength, which promotes better droplet entrapment and ensures prolonged phase separation time of the emulsion. It has been established that DHDAK, exhibiting the lowest rate of emulsion stability disruption and the highest foam stability, is the optimal candidate for use in conditions requiring prolonged stability and slow demulsification.