Glass transition behavior of octyl β-D-glucoside and octyl β-D-thioglucoside/water binary mixtures

The lyotropic behavior and glass-forming properties of octyl beta-D-glucoside (C8Glu) and octyl beta-D-thioglucoside (C8SGlu)/water binary mixtures were evaluated using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). The results clearly indicate that the mixture forms a glass in the supercooling state of liquid crystalline phases such as cubic, lamellar, and smectic. The glass transition temperature (T-g) of the mixture was strongly dependent on solute concentration, with a higher concentration correlating with a higher T-g. The experimental T-g was consistent with the predicted value calculated using the Couchman-Karasz equation in both the C8Glu and C8SGlu/water mixtures. The change of heat capacity at T-g showed the two bending points under variation of concentrations. And the highest temperature of phase transition from lamellar to isotropic solution was observed at around 50% molar concentration. It was expected that non-percolated state of water existed in extremely higher concentration ranges. (C) 2010 Elsevier Ltd. All rights reserved.