As for gels possessing rotaxane-cross-links (or topological cross-links) of which characteristics are movable polymer chains at the cross-link points, that have recently collected much attention, the synthetic methods of them are summarized mainly from the viewpoint of gelator. In addition, the application of the methods to the synthesis of gels showing thermo-responsibility and recyclability and their properties are described for the discussion on the meaning of the rotaxane-cross-link.

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Recent trend of organogelators and their applications were described. The relationship between physical gelation of solutions and crystallization was explained. Crystallization is a phenom enon that crystals are separated from solution by completely three-dimensional arrangement of solute through intermolecular interactions. On the other hand, physical gelation is caused by trapping solvent in fibrous networks which are formed by gelator molecules through intermolecular interactions. Driving forces for both gelation and crystallization are cooperating noncovalent interactions, such as hydrogen bondings, van der Waals interaction, electrostatic interaction, and π-π interaction.
New concept “gelation-driving segments” was proposed. On the basis of the concept, many functional gelators can be prepared easily from gelation-driving segments.
Gelators forming semi-permanent stable gels were developed by using polymers and oligomers, which do not precipitate as crystals from the solutions because of their molecular weight distribution and movement of flexible chains. Polymer type of gelators forming stable gels were synthesized by connecting gelation-driving segments onto polymers or oligomers. Gelation behavior was studied in detail in the three component mixed solvents composed of glyceride as polar solvent, liquid paraffin as non-polar solvent, and decamethylcyclopentasiloxane as silicone oil.
Finally, gelation-driving segment was prepared and the specific was studied.

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Dextrin fatty acid ester and inulin (fructo-oligosaccharide) fatty acid ester are used for cosmetics mainly for oil gelling agents. Difference between the types and combinations of saccharides and fatty acids affects the hardness, thixotropic, and transparency of the oil gels.

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Wax/oil gel, which contains oil in its three-dimensional structure of wax crystal, has many valuable applications in various cosmetic products, including lipsticks. This article describes the nanostructure of wax crystal which is markedly affected to the characteristics of lipsticks. It also describes a new high performance lipstick which has fine and uniform wax/oil gel structure controlled by using a novel amorphous polypropylene.

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