Advanced functionalization strategies of chitin and chitosan toward sustainable nanocomposites

Chitin, acknowledged as the second most abundant natural polymer on Earth, is extensively found in marine organisms including crustaceans, fungi, and corals. Its distinctive chemical structure imparts remarkable mechanical strength, biodegradability, and biocompatibility, rendering it exceptionally well-suited for applications in nanotechnology. However, the intrinsic insolubility of chitin in conventional solvents poses a considerable obstacle to its direct application. To overcome this challenge, nanofibrillation and chemical modification play a vital role in addressing this limitation. Furthermore, chitosan, a derivative of chitin, has broadened its application range in functional materials owing to its solubility and biocompatibility. This review provides an in-depth examination of chitin's chemical structure and extraction methods, with a focus on their functionalization strategies. Moreover, we highlight its breakthroughs in flexible electronic devices, biomedical materials and degradable plastics, aiming to provide valuable insights and references for future research in chitin-related fields.