  Self-assembled fibrillar network (SAFIN) hydrogels and organogels are
commonly obtained by a crystallization process into fibers induced by external
stimuli like temperature or pH. The gel-to-sol-to-gel transition is generally
readily reversible and the change rate of the stimulus determines the fiber
homogeneity and eventual elastic properties of the gels. However, recent work
shows that in some specific cases, fibrillation occurs for a given molecular
conformation and the sol-to-gel transition depends on the relative energetic
stability of one conformation over the other, and not on the rate of change of
the stimuli. We observe such a phenomenon on a class of bolaform glycolipids,
sophorosides, similar to the well-known sophorolipid biosurfactants, but
composed of two symmetric sophorose units. A combination of oscillatory
rheology, small-angle X-ray scattering (SAXS) cryogenic transmission electron
microscopy (cryo-TEM) and in situ rheo-SAXS using synchrotron radiation shows
that below 14$^\circ$C, twisted nanofibers are the thermodynamic phase. Between
14$^\circ$C and about 33$^\circ$C, nanofibers coexist with micelles and a
strong hydrogel forms, the sol-to-gel transition being readily reversible in
this temperature range. However, above the annealing temperature of about
40$^\circ$C, the micelle morphology becomes kinetically-trapped over hours,
even upon cooling, whichever the rate, to 4$^\circ$C. A combination of solution
and solid-state nuclear magnetic resonance (NMR) suggests two different
conformations of the 1'', 1' and 2' carbon stereocenters of sophorose,
precisely at the $\beta(1,2)$ glycosidic bond, for which several combinations
of the dihedral angles are known to provide at least three energetic minima of
comparable magnitude and each corresponding to a given sophorose conformation.
