Calcium Carbonate Mineralization Induced by Chiral Chitin Films and the Fabrication of High-Performance Composites

The natural exoskeletons of crustaceans achieve outstanding synergy between strength and toughness through hierarchically organized organic–inorganic assemblies, but their micro- and nanoscale reinforcing effects are difficult to effectively scale up to bulk macroscopic materials. Inspired by the biomineralization process of natural exoskeletons, the preparation of chitin/calcium carbonate composites and the relationship between their structure and properties were investigated. First, needle-like nanochitin whiskers were prepared, with lengths of approximately 500–600 nm and widths of about 30–40 nm. A 4wt% suspension could form a chiral chitin film with helicoidal structural features through evaporation-induced self-assembly. Calcium carbonate mineralization was then induced at different temperatures. At the initial stage of mineralization, mineralized spots formed on the surface of the chitin film; as the mineralization time increased, these spots gradually developed into a dense mineral layer. The mineralization product obtained at 25℃ was mainly calcite, whereas vaterite-like features gradually became more pronounced under conditions of 37–60℃. Finally, using sodium alginate as an interlamellar binder, the chitin films mineralized at 60℃ were assembled into a bulk material. Its flexural strength increased from 18 MPa for the pure chitin bulk material to about 38 MPa, while the flexural modulus increased from about 0.8–0.9 GPa to about 3.7 GPa. Using a self-assembled chiral lamellar chitin scaffold as a template, CaCO₃ confined mineralization was achieved at low temperature, followed by the fabrication of high-performance composites via sodium alginate bonding and pressure-assisted assembly.