Lipoaminoacid surfactants: Phase behavior of long chain N^α-Acyl arginine methyl esters

Abstract

Long chain N^α-Acyl-L-arginine methyl esters are cationic lipoaminoacid surfactants obtained in our laboratories by condensation of a fatty acid with the α-amino group of L-Arginine. As part of systematically studying the properties of these surfactants, their phase behavior in binary and multicomponent systems has been investigated as a function of chain length of the fatty acid residue. It has been found that Krafft temperature and critical micelle concentration (CMC) increase and decrease respectively with the increase in the alkyl chain length, as expected in a homologous series of surfactants. The N^α-Myristoyl-L-arginine methyl ester (MAM)/water phase diagram showed three liquid crystalline regions with hexagonal, cubic, and lamellar structures. Phase behavior of ternary N^α-Acyl arginine methyl ester/water/n-alkanol systems was found to conform to that of ionic surfactant systems. Microemulsion formation was investigated in quaternary N^α-Lauroyl-L-arginine methyl ester (LAM)/water/n-alkanol/hydrocarbon systems.