Self-assembly of azobenzene-based two-component gels

Abstract

An azobenzene derivative was found to form a two-component gelator with lauroyl or stearoyl phenylalanine although phenylalanine units failed to gel the solvent. During gelation, the yellow sols turned into red gels, implying a sharp color change in the system. In gel, molecules self-assembled into one-dimensional nanofibers. Circular dichroism spectral results indicated that the chirality of phenylalanine was passed on to the azobenzene moiety, which formed a right-handed helical stacking in the gel phase. UV-vis experiments and NMR spectra revealed that the azobenzene derivative and lauroyl phenylalanine formed a complex with a ratio of 1 : 4. The critical gelation concentrations and gel-to-sol phase transition temperatures were dependent on the ratio of the two compounds. Moreover, the response of two-component gels to mechanical stimulus could result in a gel-to-sol transition. The gels can again self-heal after resting, which is a process that can be reversed numerous times.