Effects of hydration of sugar groups on the phase transition of the bilayer formed from alkyl glycoside.

Abstract

Two alkyl glycosides cetyl-β-glucoside (C16-Glu) and cetyl-β-galactoside (C16-Gal), were synthesized and the thermal properties of their water systems were examined using differential scanning calorimetry (DSC). These compounds form bilayer structures. The C16-Glu − H2O system shows five endothermic peaks due to the phase transition from gel to a liquid crystalline state at 86, 73, 68, 57, and 47°C, depending on the amount of added water, i.e., the degree of hydration. In the samples containing enough water, which means that free water coexists with hydrated water, the lowest two peaks at 47 and 57°C were observed and their intensity ratio changed in each run depending on the thermal history of the sample. It was explained by the presence of two kinds of hydrated states. An ESR study of the TEMPO parameter showed that these transitions come partly or wholly from the melting of the alkyl chains. The C16-Gal − H2O system showed three peaks, but did not show any hysteresis. The difference between C16-Glu and...