PHASE-BEHAVIOR, LYOTROPIC PHASES, AND FLOW PROPERTIES OF ALKYL GLYCOSIDES IN AQUEOUS-SOLUTION

Micellar aggregation, theological properties, and phase behavior of tw o commercially available alkyl polyglycosides (APG Trade name of Henke l KGaA, Dusseldorf) have been studied. Light scattering and viscosity measurements show that the short chain C-8/10-APG (n = 8-10) forms up to high surfactant concentrations spherical micelles which are highly hydrated whereas the long chain C-12/14-APG (n = 12-14) forms rodlike micelles above 0.04 wt % surfactant. The isotropic phase of C(8/10)APG which extends to 98 wt % above 20 degrees C is a Newtonian liquid. C- 12/14-APG solutions are viscoelastic even at low concentrations. The l iquid crystalline phases which appear at high surfactant concentration s (C-8/10-APG 75-85 wt % below 20 degrees C, C-12/14-APG above 60 wt % at all temperatures) are characterized by their polarization microsco pic textures. As well as in ternary surfactant-fatty alcohol-water sys tems we find three different lamellar regions with three characteristi c textures. Only the Lah region is able to generate the pseudoisotropi c orientation between two glass surfaces which is characteristic for i sotropic lamellar planes. Polarization microscopic pictures of the L(a lpha l-h) region show a broken focal conic texture of thermotropic sme ctic-E phases. The L(alpha l) region has a biaxial woven or a schliere n texture, similar to that of a nematic rod phase, which is characteri stic for thermotropic smectic-C phases.