Polymer networks characterized by slidable crosslinks and the asynchronous dynamics of interlocked components

In mechanically interlocked molecules like rotaxanes and catenanes, each component has asynchronous microscopic motion within the topological restrictions. The motions can be expressed macroscopically by incorporating the mechanically interlocked molecules in polymers and their networks. Rotaxane develops into polyrotaxane having a polymer axis, and then polyrotaxane forms a polymer network so-called slide-ring material. Because the polymer chains in the material are topologically connected to each other via a figure-eight crosslink, the chains can slide through the crosslink. This microscopic slidability at the crosslink drastically affects the mechanical properties. This article first presents an overview of significant studies on slide-ring materials in the first decade that deal with single species material consisting of polyethylene glycol and α-cyclodextrin. These studies have revealed abnormal statics and network structures, most of which can be interpreted in terms of slidability. Next, we describe our recent designs of materials and findings in mechanical properties attributed to the slidable crosslinks that are built on a synthetic breakthrough that yields a new series of slide-ring materials composed of various backbone polymers. The finding of a sliding transition reveals the dynamics of sliding, the significance of the entropy of uncrosslinked cyclic compounds, and helps in determining the mechanical properties of slide-ring materials.