| During the last decade, physical gels prepared by small molecular gelators have attracted more and more attention. As an important branch of physical gel, stimuli-responsive gels, which inculde hydrogels and organogels, have been extensively investigated and have potential applications in smart biomaterials and drug-delivery systems. As one of the special gels, the heat-set organogels which are formed at high temperature in organic solvents have received increasing attention for their great potential applications in materials, medicines and other fields. The heat-set organogels inculde two types. One is irreversible gels, which is usually prepared by polymers, particularly proteins. The other is reversible gels, which is usually prepared by small organic molecules.This paper mainly introduced two new thermally reversible gel systems and preliminary research on their modification. Firstly, we introduced a new reversible, heat-set organogel based onβ-CD. The gel system is a thermal responsive organogel of small organic molecules formed by a system of DPA withβ-CD and LiCl in DMF. DPA could be gelated in DMF particularly as the temperature increasing, while be dissolved again with the temperature decreasing whenβ-CD and LiCl are introduced into the system. This is very interesting and unusual for that DPA,β-CD and other organic molecules dissolve respectively very well in DMF, particularly as the temperature increases. The gel system as the first heat-set small organic molecules organogel based onβ-CD was characterized by OM, SEM, DSC, XRD, FT-IR. The appealing features of this new kind of gel are described as follows. (1) It is a multicomponent system where each of the four components is required for the organogelation property. (2) The gel system is formed by simple, small, and commercially available chemicals. (3) It is a thermo-responsible organogel of small organic molecules, which is different from the conventional gels dissolved upon heating. The sample is a transparent solution at room temperature, but a gel can be formed when it heated to a Tgel(the temperature of gelation). (4) It could be reversible to temperature, which was confirmed by DSC. When the temperature is lower than the Tgel, the gel could turn to a solution again. (5) It is responsive to the amount of LiCl. There's no gel could be formed without the presence of LiCl. (6) It is responsive to the guest molecules. Generally, the Tgel decreased by adding the guest molecules into the gel system, but some guest molecules, whose structure is exactly fitted to the cavity of CDs, could destroy the gel formation of the gel system.Secondly, we introduced a triple-transforming gel system (gel-sol-gel) for the first time, which is a thermo-responsive organogel with multi-components prepared byβ-CD, DPA and LiCl in DMAC in a suitable proportion based on the supramolecular interactions. The conventional thermo-responsive gels is duplicate-transforming (sol-gel), which could be thermo-reversible by one way of heating or cooling around the gelation temperature (Tgel), or the other way of heating upon Tgel and cooling down. The first gel (gel A) could be formed byβ-CD, DPA and LiCl in DMAC at room temperature based on stirring, then the gel could transform into a clear solution based on heating, and then the other gel (gel B) can be formed at a relatively high temperature (Tgel, the gelation temperature by heating). This gel system was characterized by OM, SEM, FT-IR and Rheology. Some significant features of the gel system were found as follows:(1) the system has multi-components, where each of the four components is required for the organogelation; (2) the system is a thermo-responsive organogel of small organic molecules such as DPA and DMAC, which is different from the conventional gels with a duplicate-transforming (sol-gel) process; (3) the two gel states have different micro-structures observed by SEM. The striking self-assembly properties of the thermo-responsive triple-transforming system may bring in much broad prospects for applications.Finally, we have modified the two gel systems simply by modifying the gelators or replacing the gelators. Based on the modifications, we could indicate the possible mechanism for gel formation and explore for more excellent gel system.
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