Recent Progress and Future Perspective in Slide-Ring Based Polymeric Materials

Polymeric materials, often represented as thread-like molecules, are frequently utilized as network structures through the chemical or physical cross-linking of polymer chains. Recently, materials incorporating rotaxanes or polyrotaxanes─quintessential topological supramolecular structures─into this cross-linked architecture (termed Slide-Ring Materials, SRMs) that exhibit distinct physical properties compared to materials directly cross-linked by conventional polymer chains have emerged. The mobility of the cross-linking points allows for the redistribution of tensile and compressive stresses exerted on the polymer chains, thereby enhancing the toughness and durability of the material. In addition to the conformational entropy of the polymers, which underpins rubber elasticity, the entropy of the rings also contributes to the elasticity, resulting in various physical properties that diverge from traditional materials with fixed cross-links. Initially introduced as gels, materials with movable cross-links have subsequently expanded to rubbers, elastomers, resins, and composites. Research has also intensified on materials that not only consist solely of rotaxanes or polyrotaxanes but also those that incorporate small quantities of rotaxanes or polyrotaxanes into conventional polymer materials. Particularly, the latter has become significant especially in terms of application for various fields, as it retains the myriad advantages of traditional polymer materials while achieving enhanced toughness, making the application of SRMs highly advantageous. In this perspective, we review recent advancements in the synthesis, structure, properties, and functions of SRMs, and briefly touch upon the future prospects of SRMs.