Dynamic Evolution of Coaxial Nanotoruloid in the Self-Assembled Naphthyl-Containing l-Glutamide

Supramolecular gelation provides an efficient way of fabricating functional soft materials with various nanostructures. Amphiphiles containing naphthyl group and dialkyl l-glutamide with a methylene spacer, 1NALG and 2NALG, have been designed and their self-assembly in various organic solvents were investigated. Both of these compounds formed organogels in organic solvents. In the case of the alcohol solvents, the initially formed organogel underwent gel-precipitate transformation, which process was monitored by the UV-vis, CD spectra, and SEM observation. It was revealed that both the compounds formed the nanofiber structures in gel phases. Interestingly, in alcohol solvents, during the phase transition from the gel to precipitates, the nanofibers gradually transformed into a series of long coaxial solid nanotoruloid, a unique nanostructure that has never been observed in other self-assembly systems. In addition, during the gel formation, the nanofibers with supramolecular chirality or M-chirality were obtained. However, the coaxial nanotoruloid showed an inversed P-chirality. Comprehensive analysis based on various data and the gelator structure, substituent position, type of organic solvents, it was suggested that the synergistic interactions between the amide H-bond and π-π stacking of the naphthyl groups played important roles in the formation of the gels as well as the nanofiber, while the H-bonding ability of alcohol to the amide group can subtly regulate the gelator-gelator interactions and lead to the dynamic and hierarchical evolution of the unique nanostructures.