Cyclodextrin-Based Rotaxanes: from Rotaxanes to Polyrotaxanes and Further to Functional Materials

This minireview overviews rotaxanes and pseudorotaxanes containing cyclodextrins (CDs) as the rotor component. Since CDs interact with molecules, e.g., hydrophobic compounds of the size and shape matching their cavity, to form inclusion complexes in aqueous media, CDs are an important class of macrocyclic compounds as rotor components of rotaxanes and pseudorotaxanes. Research on CD-based rotaxanes has begun with the synthesis of rotaxanes from low molecular weight axis molecules and then developed into the construction of molecular machines and polyrotaxanes. Recently, the research has further developed into macroscopic functional materials, e.g., slide-ring gels, macromolecular assemblies, self-healing materials, and soft actuators. In the present article, typical examples of CD-based rotaxanes and pseudorotaxanes are described; synthesis of rotaxane and construction of molecular machine are described in Section 2, synthesis of polyrotaxanes is dealt with in Section 3, and development of macroscopic functional materials based on rotaxane structure is discussed in Section 4.