Polyrotaxanes in motion: recent advances in slide-ring supramolecular polymers
Zhi-Min Lv, Yue-Yang Liu, Sun‐Kyoung Yu, Jia Tian, Yun‐Xiang Xu, Zhan‐Ting Li
Abstract
Polyrotaxanes (PRs) are mechanically interlocked supramolecular systems with the ring components threading linear axle component. When two rings are connected with a covalent linker and incorporating PRs into main-chain or side-chain polymers, the sliding of the rings over the threaded covalent networks produces pulley effect, by which the polymer chains can pass through the rings to equalize the tensions cooperatively and avoid localization of the stress. Since the pioneering work on the α−CD/polyethylene glycol-composed system by Okumura and Ito in 2001, such slide-ring supramolecular polymers (SRSPs) have been developed as a new kind of mechanically interlocked materials that display specific conformational freedom, high movability, as well as exceptional mechanic performances, which include enhanced toughness, stretchability, recoverability and self-healing ability. In addition to α−CD, β−CD, crown ethers, pillar[5]arene, and discrete macrocycles have been used as the ring components. A diversity of sliding and interpenetrating patterns has also been developed. With the establishment of the preparation methods and structure-property relationship evaluations, SRSPs have been vigorously explored as promising materials for a variety of functions and applications, including anti-scratch, anti-fracture, anti-puncture and anti-impact, as well as enhanced hydrogels, rubbers and elastomers. In this review, we summarize recent progresses, mainly those obtained in the past five years, in the preparations, structures, functions and applications of this family of supramolecular polymers. In the final section, we give our perspectives of future research and challenges.