Structure and dynamics of polyrotaxane and slide-ring materials

Polyrotaxane (PR), in which cyclic molecules are threaded into a linear polymer chain, has generated great interest because the sliding and rotation of the cyclic molecules on the axial polymer chain lead to unique functional nanomaterials with novel dynamical properties. A typical example of the functional materials is a polyrotaxane network, called slide-ring (SR) material, prepared by cross-linking the cyclic molecules on different PRs. The cross-links composed of two cyclic molecules in a shape of figure-of-eight slide along the polymer chains and the sliding motion gives rise to remarkable physical properties of the SR materials. In order to understand the unique features of the functional materials including SR materials and develop novel applications of PR, it is necessary to reveal the physical properties of PR, especially the sliding motion of the cyclic molecules in PR. In this article, we review the static structure and molecular dynamics of PR based primarily on our recent studies. Furthermore, the difference between SR materials and usual chemical gels in deformation behavior is also described. The findings summarized in this review indicate the significance of the sliding motion of cyclic molecules characterizing PR and SR materials.