ABSTRACT Biodegradable and low‐irritant amino acid–based surfactants have attracted considerable attention as environmentally friendly alternatives to conventional petroleum‐derived surfactants. In this study, a series of acyl amino acid surfactants with identical amino acid head groups but different alkyl chain lengths were synthesized via a modified Schotten–Baumann condensation between fatty acyl chlorides and glycine as amino acids under alkaline conditions. The synthesis was conducted using lauroyl chloride and myristoyl chloride mixtures with molar ratios of 10:0, 9:1, 8:2, and 7:3 to investigate the effect of alkyl chain composition on interfacial properties. The obtained products, easily purified by phase separation, were characterized by Fourier transform infrared spectroscopy (FT–IR), proton nuclear magnetic resonance spectroscopy ( 1 H NMR), and electrospray ionization mass spectrometry (ESI–MS). Surface tension, foaming ability, and foam stability were systematically evaluated. Surface tension measurements revealed comparable surface excess values for all compositions, while the critical micelle concentration showed a non‐monotonic dependence on chain ratio, with a minimum at the 9:1 composition. Foaming tests demonstrated enhanced foamability and good foam stability for the mixed systems, particularly at the 9:1 ratio. These results highlight the importance of mixed alkyl chain composition in designing efficient and sustainable amino acid–based surfactants.
Takeshita et al. (Wed,) studied this question.