Macrocycle-based cross-linked supramolecular polymers: an overview

Cross-linked supramolecular polymers (CLSPs) are a special type of materials that combine the improved mechanical stability of covalently cross-linked network polymers with the dynamic and reversible interactions of supramolecular chemistry. In this review, the structures and characteristics of CLSPs are examined, with an emphasis on macrocycle-based architectures such as crown ethers, pillar[5]arenes, cryptands, cucurbiturils, calix[n]arenes, and calix[4]pyrroles. Among these macrocycles, calix[4]pyrrole-based CLSPs are important because they can interact with both neutral and anionic guest species, which endows them with unique binding characteristics, in contrast to other macrocycles that form complexes with cationic species. We focus on key examples from the recent literature, showing their crosslinking strategies and the properties of the resulting materials. We also emphasize the various applications of CLSPs in stimuli-responsive systems, self-healing materials, and biomedical applications. This review also highlights the potential of CLSPs as functional materials in the context of recent developments.