Surface-Active Amidequats with an Alkoxymethyl Substituent: Synthesis, Analysis, and Preliminary Evaluation as Potential Emulsifiers and Substitutes for Conventional Surfactants

Amidequats have attracted considerable attention in research; however, their surface activity remains largely unknown, and their potential as emulsifiers is still unexplored. In this work, series of novel surface-active amidequats based on ecofriendly caprylic acid were synthesized and their micellization behavior in water was explored systematically. The surface tension, wettability, foamability and stability, and measurements of melting and crystallization temperatures were employed to characterize the compounds. The functionalization of amidequats containing an alkoxymethyl substituent significantly enhances micellization properties compared to the structurally analogous anionic surfactant, sodium caprylate. Moreover, for optimized molecule geometries, electrical dipole moments were determined and correlated with surface activity. Experimental and theoretical studies indicate that amidequats with 12 carbon atoms in the alkyl chain exhibit the highest surface and foam-forming activity, making them promising emulsifiers. Due to this fact, oil-in-water (o/w) or water-in-oil (w/o) emulsions using the mentioned amidequat were prepared, and their rheological analysis, ζ potential, topography analysis, and particle size were studied. A detailed investigation of the surface properties of amidequats was undertaken to assess their potential application in the cleaning agent and cosmetic industries.