Structural Studies of 1,3:2,4-Dibenzylidene Sorbitol Gels

Abstract

We investigated the self-assembled structures of 1,3:2,4-dibenzylidene sorbitol in different solvents by using synchrotron small-angle X-ray scattering (SAXS) and optical microscopy. Structures of a turbid gel and a nearly transparent gel were compared in this study. Although the sol-gel transition temperatures of both gels showed almost the same values, their structures were largely different. The optical microscopy observation showed that a spherulite structure was formed for the turbid gel, but for the transparent gel no distinct structure was seen in the scale of optical microscopy. The SAXS experiments reveal that the transparent gel was composed of fibrillar aggregates with the radius of gyration Rc of 38-40 Å in the cross-section. The increase in temperature in the gel state caused decrease in the fiber density with keeping the fiber thickness almost unchanged, and the fibrillar aggregates were completely dissolved above the sol-gel transition temperature. The cross-sectional size became more homogeneous, as the temperature approached the sol-gel transition temperature.