Surface active properties and micellar aggregation of alkyl 2-amino-2-deoxy-beta-D-glucopyranosides

A series of alkyl 2-amino-2-deoxy-beta-D-glucopyranosides having n-alkyl chain lengths of 8, 9, or 12 carbon atoms have been studied in pure water solutions and at different temperatures. The measured critical micellar concentrations (cmc's), areas at the air-water interface (a(0)), and micellar aggregation numbers show little dependence on temperature. The cmc decrease with respect to alkyl chain length is similar to that of nonionic surfactants. The ao values are on the order of 50 A(2)/molecule, irrespective of the alkyl chain length. Aggregation numbers are significantly larger than the Tanford limit for spherical micelles. pH measurements show the low protonation of the amino group in pure water above the cmc. These glucosamine-based surfactants behave as typical neutral alkyl glucosides; headgroups are close packed at interfaces, leading to large micelles as compared to other types of surfactants of similar hydrophobic chains.