Polymeric Rotaxanes

Various types of polyrotaxanes were studied according to their structures and components. Main chain polyrotaxane with cyclodextrin (CDs) are a family of macrocyclic oligosaccharides, the most common of which are composed of 6 (α), 7 (β), or 8 (γ) α-1,4-linked D-glucopyranose units. Construction of polyrotaxanes using CDs can be categorized in three types, the threading approach, slipping approach, and inclusion polymerization approach. The major driving forces for forming CD inclusion complexes are hydrophobic and van der Waals interactions between the inner surface of the CD ring and the hydrophobic sites of the guests. Metal ions play an important role to expand the rotaxane structures into the higher-ordered polyrotaxane frameworks. One class of polymeric rotaxanes consists of side chain polyrotaxanes and polypseudorotaxanes. Side chain polyrotaxanes and polypseudorotaxanes are categorized into the three systems, rotor/polyaxis systems, polyrotor/axis systems, and polyrotor/polyaxis systems.