Rapid and reversible gel-sol transition of self-assembled gels induced by photoisomerization of dendritic azobenzenes

Enzymatic formation of a photoresponsive supramolecular hydrogel

This paper reports the first example of the use of an enzymatic reaction to generate a photoresponsive hydrogelator, which represents a convenient route to expand the scope of optically controlled molecular self-assembly in water.

Tuning the helicity of self-assembled structure of a sugar-based organogelator by the proper choice of cooling rate

A novel sugar-appended low-molecular-mass gelator, 4''-butoxy-4-hydroxy-p-terphenyl-beta-D-glucoside (BHTG), was synthesized. It formed thermally reversible gels in a variety of aqueous and organic solvents. Three-dimensional networks made up of helical ribbons were observed in the mixture of H(2)O/1,4-dioxane (40/60 v/v). The handedness of the ribbons depended on the rate of gel formation. Fast-cooling process led to right-handed ribbons, while slow-cooling process led to left-handed ones. A combinatory analyses of microscopic, spectroscopic, and diffraction techniques revealed that BHTG formed a twisted interdigitated bilayer structure with a d spacing of 3.1 nm in gels through a kinetically controlled nucleation-growth process. There were two kinds of molecular orientations of BHTG in the nuclei, clockwise and anticlockwise, which dictated the growth of ribbons. One was metastable and formed first during the cooling process of gel formation. It was able to gradually transform into the more stable latter one with further decreasing temperature. Fast-cooling process did not leave enough time for the nuclei to evolve from metastable to stable state and the ribbons grown from them exhibited right-handedness. However, the metastable nuclei transformed into the stable one when cooled slowly and directed the molecules of BHTG to grow into left-handed aggregates.

Sonication-induced molecular gels based on mono-cholesterol substituted quinacridone derivatives

A series of monocholesterol substituted quinacridone derivatives MCC(n) (n = 4, 6, 8) has been designed and synthesized. Compounds MCC(6) and MCC(8) can gelate a wide range of organic solvents upon ultrasound irradiation and afford intriguing well-defined nanostructures composed of three-dimensional sponge-like superstructures or fibrous networks. Interestingly, the gel produced from MCC(6) is sensitive to thermo-, aniline, and formic acid stimulus, giving obviously different aggregation behaviors as well as physical properties. Time-dependent spectroscopic data and theoretical calculation results provided explanation for the possible molecular aggregation mode during the formation of the gels.