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A unique b-cyclodextrin (b-CD) gel with ordered structure was fabricated. The ordered aggregation of b-CD was achieved by controlling the solubility of b-CD in good/poor solvents. Physicochemical properties of the gel were systematically investigated. Mechanical properties were tested by rheological measurements, and the fibrous morphology was observed by confocal laser scanning microscopy. The anisotropic property of gel fibers was detected under polarized optical microscopy. Well-defined tetragonal and channel packed microstructures were formed in gel fibers, which revealed hollow channels of cyclodextrins. By changing physicochemical environments, macroscopic phase transitions were aroused, and self-recovering phenomena occurred when a certain amount of NaCl was added into the gel as a stimulus or the shear rate loop test was performed (thixotropy). By adjusting the concentrations of external stimuli or volume ratios of good/poor solvents, properties of the gel including mechanical strength or thermostability can be easily altered. The ordered empty channels assembled by CDs with the self-recovering properties may shed new light on this traditional host molecule.

The controllable self-growth of a supramolecular hydrogel of folic acid (FA) was developed based on the conduction of transition metal ions. The growth behavior of the gel could be flexibly controlled by adjusting the ambient environmental factors such as gelator concentration, temperature and external chemical stimuli. The obtained gel was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM) and rheological measurements. Differential scanning calorimetry (DSC) showed that the gel possessed excellent thermal stability. A mechanism for the fibrous formation of the gel was suggested based on the experimental results of Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR) and UV-Vis spectroscopy.The gel exhibited multiple stimuli-responsive properties to changes in ligand and pH. Furthermore, the gel can be incorporated into multi-layer hydrogels in both artificial and spontaneous ways, showing the advantages of self-growth and flexible control of the gel system. This novel hydrogel and the preparation strategy may provide a new route to rationally design advanced materials for biomedical applications.

This paper describes a novel double phase transforming organogel (gel-sol-gel') composed of nontoxic β-cyclodextrin, potassium carbonate, and 1,2-propylene glycol. The gel-sol-gel' transforming processes are followed by a reversible gel-sol transforming process and an irreversible sol-gel' transforming process based on heating. The gel-sol-gel' transformation is accompanied by microstructure changes from nanospheres to nanorods. K(2)CO(3) plays a key role in associating supramolecular architectures of β-cyclodextrin into a three-dimensional network. This work may bring further applications in the areas of smart materials, drug delivery systems, and biomaterials.

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