THE PHASE-TRANSITION IN THE GEL STATE OF THE 1,3-2,4-DI-O-BENZYLIDENE-D-SORBITOL ETHYLENE-GLYCOL SYSTEM

In chiral oil gelators, only 1,3:2,4-di-O-benzylidene-D-sorbitol (D-DBS) can form gels with alcoholic solvents. The D-DBS concentration dependence of the state in the binary system D-DBS/ethylene glycol, were studied using optical, rheological and spectral measurements. Based on the changes in the transmission and mechanical properties, two phase transition points, which depended upon the D-DBS concentration, were observed at 10 and 30 mM. The low-concentration point was the critical gel concentration. The gel was formed above 10 mM. D-DBS formed spherical domains in the gel between 10-30 mM and made continuous crystals on the entire gel above 30 mM. The aggregated structure of D-DBS in ethylene glycol was studied, utilizing electronic and circular dichroism measurements. According to the gelation, the absorption of the transition moment along the long axis of the benzene ring was red-shifted. The relative orientation changed in 10-30 mM from the hyperchromism and hypochromism of the electronic absorptions, but was fixed above 30 mM. D-DBS exhibited remarkable CD enhancements due to the formation of a gel. The concentration dependence of the molar ellipticities of the CD absorptions was similar to the tendency of the electronic spectra. This indicated that the aggregated structure was changed, depending upon the D-DBS concentration in ethylene glycol; the optical and mechanical properties were related to the aggregated structure which D-DBS formed.