Phase equilibria and physical-chemical properties of sugar-based surfactants in aqueous solutions

A study of solution properties of 3 nonionic surfactants derived from glucose is reported. These surfactants, from a series of 6-O-acyl-alpha,beta-D-glucopyranoses, differ from one other by the number of carbon atoms in their alkyl chain: 6-O-decanoyl-, 6-O-stearoyl- and 6-O-oleyl-. The surface properties [critical micellar concentration (cmc) and minimal area/molecule at air-water interface (am;)] were investigated in water at 42 degreesC by means of surface tension measurements. Partial phase diagrams and liquid-crystalline mesophases were studied in heavy water using polarising microscopy, H-2-NMR spectra and DSC measurements. All binary systems form a lamellar lyomesophase in a wide range of composition. A Gel --> Lamellar phase transition was observed as the temperature was increased only on the 6-O-decanoyl-D-glucopyranose/D2O system. The Gel-Lamellar transition temperatures were checked by DSC thermograms. Molecular self-diffusion of surfactant and water in the micellar solution phase of 6-O-decanoyl-D-glucopyranose/D2O system were determined at 35 degreesC by Fourier transform pulsed gradient spin-echo H-1-NMR spectroscopy. From this study it has been possible to draw conclusions about the changes on the solution microstructures as function of surfactant concentration. (C) 2002 Elsevier Science B.V. All rights reserved. OI sindona, giovanni/0000-0002-5623-5795