Some methyl 4,6-O-benzylidene monosaccharides can act as strong low molecular weight gelators for various organic solvents. As they are accessible in a variety of homologues, each with a unique molecular architecture, they can be used for systematic studies of gelation phenomena. Structural details of their hydrogen-bond-based fiber network in the gel phase can be resolved by small angle X-ray scattering (SAXS). Analysis of the molecular arrangement in a single crystal can be a valuable tool for the prediction of gelation ability presupposing that the elongated shape of the gel fibers arises from an anisotropic assembly of the gelator molecules into one-dimensional aggregates. It is found that some derivatives act as "supergelators", which can gelate hydrocarbon solvents with 0.03-0.05 wt%. The recent results emerging from these investigations will be outlined in this article.

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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”.