Supramolecular structure of a sugar-appended organogelator explored with synchrotron X-ray small-angle scattering

Small-angle X-ray scattering (SAXS) from an organogel system prepared from methyl 4,6-O-benzylidene-α-D-mannopyranoside and p-xylene was carried out with a synchrotron X-ray source at SPring-8, which revealed that hexagonally packed fibrils are formed in the gel state. The spacing between the fibrils can be evaluated to be about 60 Å, and this value was almost independent of both the gelator concentration and the temperature. Furthermore, the spacing is larger than the gelator molecular size. Upon heating, this supramolecular structure completely disappeared. Time-resolved SAXS revealed that phase separation takes place initially and subsequently the hexagonal structure is formed. Wide-angle X-ray diffraction (WAXD) showed that there is no crystalline peak at all and the diffraction pattern is consistent with being amorphous. ¹H NMR spectral data show that the gelator molecules still maintain thermal motion in the gel state. The present SAXS, WAXD, and NMR results contrast with those of "dry gels" in which the gel fibers consist of the crystal of the gelators. Our results suggest that the solvent molecules are incorporated into the gel fiber and the present gel can be classified as a "wet gel".