Vicinal solvent effect on supramolecular gelation: alcohol controlled topochemical reaction and the toruloid nanostructure.

Although solvent is the major component of the gel, it still remains unclear how the solvent molecules take part in the formation of the gel nanostructures in many gels. In this study it was observed that the vicinal effect on gel formation as well as their nanostructures, that is, the vicinal solvent molecules to the gelator, determine the molecular packing and their subsequent structures and properties. A naphthylacryl-conjugated L-glutamide gelator was found to form organogels in various solvents and nanofiber structures. While the nanofibers from other solvents could not show any further reaction, the gel from the alcohol could undergo topochemical [2+2] cycloaddition under photoirradiation and resulted in toruloid nanostructures. Various pure alcohol solvents from methanol to pentanol were found to show a similar property. Interestingly, switching from a single alcohol solvent to mixed solvents of alcohol with miscible or immiscible non-alcohol solvents could still cause the same change, showing the vicinal effect of alcohol on controlling the molecular packing as well as the structural transformation. More interestingly, when nanofiber xerogel, obtained from non-alcohol solvents, was exposed to alcohol vapor, the nanofiber was transferred into nanotoruloid. These results provide a new insight into the gelator-solvent interaction in soft gels.