Advances in the Chemical Properties and Functional Applications of Urushiol: From Traditional Lacquerware to Modern Materials

Urushiol, the key component of natural lacquer, is emerging as a versatile bio-based phenolic platform for advanced polymer systems. Its unique catechol structure, combined with an unsaturated aliphatic side chain, provides multiple reactive sites, enabling diverse chemical pathways and tunable network architectures. This review presents a systematic analysis of urushiol-based materials within a “structure–reaction–property–application” framework. The intrinsic reactivity of urushiol, including oxidative polymerization, dynamic covalent bonding, and metal–phenolic coordination, is correlated with the formation of crosslinked networks exhibiting controllable mechanical properties, strong interfacial adhesion, and stimuli responsiveness. Recent advances in functional coatings, self-healing and reversible polymers, bioactive materials, and cultural heritage conservation are highlighted. Special emphasis is placed on dynamic network design and low-sensitization strategies to overcome limitations of traditional lacquer systems. Finally, key challenges and future directions toward controllable curing, structure–property relationships, and sustainable material design are discussed, positioning urushiol as a bridge between traditional materials and next-generation functional polymers.