Cucurbituril Based Supramolecular Polymer Gels: From Macrocycle Synthesis to Functional Composite Networks

Cucurbiturils (CB[n]) are rigid glycoluril-based macrocycles possessing well-defined hydrophobic cavities capable of forming stable host–guest complexes in water. Owing to these properties, CB[n]-containing supramolecular polymer gels have attracted increasing attention as functional composite materials in modern materials science. This review summarizes recent progress in the development of cucurbituril-based supramolecular gels, with particular attention to synthetic approaches, network design, and emerging applications. Both conventional acid-catalyzed methods and more sustainable synthetic strategies for cucurbituril preparation and functionalization are discussed. We further consider the role of CB[n] macrocycles as reversible crosslinking units in polymer networks and analyze how host–guest interactions influence the mechanical properties, self-healing behavior, and stimuli responsiveness of the resulting materials. Recent applications in biomedical engineering, soft electronics, and environmental remediation are also highlighted, demonstrating how molecular-level supramolecular interactions can determine the macroscopic performance of these composite systems. The review concludes with perspectives on scalable synthesis, processing integration, and future directions in supramolecular composite materials.