The thermal behavior of 1,3:2,4-di-O-benzylidene-D-sorbitol ethylene glycol gel

The so-called 1,3:2,4-di-O-benzylidene-D-sorbitol (D-DBS) can cause the gelation of alcoholic solvents. The thermal behavior of a 1 wt% D-DBS/ethylene glycol gel was studied using thermal, optical, mechanical, and spectroscopic measurements. Changes in the optical and mechanical properties were observed at around 45 and 80 degrees C. Upon heating, the diameter of the spherulitic texture in the gel decreased above around 45 degrees C and disappeared at around 80 degrees C. In a thermal analysis, an endothermic peak was observed at around 80 degrees C, which agreed with the gel state-isotropic solution phase-transition point. The aggregated structure of D-DBS in ethylene glycol was studied, using UV absorption and circular dichroism (CD) measurements. The relative orientation of the benzene rings changed above 45 degrees C, due to the hypochromism of the UV absorptions. The gel showed a temperature dependence of the CD spectra. With increasing temperature, the value of the molar ellipticities increased at 27-82 degrees C, and drastically decreased at 82-93 degrees C, indicating that the aggregated structure underwent a change at between 45-80 degrees C and disappeared above 80 degrees C. The macroscopic level, as well as the optical and mechanical properties were related to the change in the aggregated structure formed by D-DBS.