Polymer modified cyclodextrin-based polyrotaxanes: From functionalization to applications

Polyrotaxanes (PRs), defined by their topological structure of a linear polymer threaded through multiple cyclic molecules such as cyclodextrins (CDs) with non-covalent interactions, exhibit unique properties stemming from the mobility of the threaded macrocycles. This mobility has driven significant interest in PRs over the past decades. Since CDs are readily available in both high purities and large quantities, CD-based PRs have received more and more attentions. However, their practical application has been limited by poor processability and mechanical properties. Leveraging advanced polymerization techniques enables the modifying of polymer chains or polymeric structures onto PRs to form polymer-modified polyrotaxanes (PM-PRs). This polymeric modification enhances the solubility and processability of PRs while preserving the unique properties conferred by the mobile CDs. Furthermore, incorporating diverse functional polymers can introduce new functionalities to PRs. Critically, the mobility of the threaded CDs within the supramolecular PR structure provides key advantages. These characteristics make PM-PRs with mobile CDs highly suitable for innovative, adaptable material applications. Although numerous reviews have reported the synthesis and applications of PRs, a comprehensive review focusing on PM-PR remains unavailable. In this review, we systematically summarize (1) the synthetic strategies of PM-PRs, (2) the remarkable progresses achieved in recent decades, and (3) the diverse applications of PM-PRs as advanced functional materials. Based on structural configurations, PM-PRs are categorized into three main types: (1) block copolymer-type PRs (PM-b-PRs), where PR segments are incorporated into block copolymers; (2) grafted PRs (PM-g-PRs), featuring polymer side chains attached to the PR backbone; and (3) crosslinked PRs (PM-c-PRs), forming three-dimensional networks through inter-PR connections, with each type offering distinct advantages for developing functional materials through tailored synthetic approaches that expand their potential applications. Overall, the review intends to highlight the evolution of PM-PR and their unique properties endowed by the synergistic effect of modified polymer chains and PR structures, as well as wide applications in materials science in the past few years.