Bionanocomposite from self-assembled building blocks of nacre-like crystalline polymorph of chitosan with clay nanoplatelets

Abstract

Biopolymers are biocompatible and nontoxic but their other properties rank much below synthetic polymers. Their mechanical performance is improved significantly in bionanocomposites with a layered brick-and-mortar structure biomimicking the nacre of a crustaceous shell after integration with nanoparticles. Biopolymers are found in a disordered state, whereas crustaceans hold chitin in a crystalline form. Herein, it is biomimicked in a bionanocomposite of chitosan with clay nanoplatelets. Films were prepared using a new one-pot technique combining an initial formation in situ of building blocks of clay nanoplatelets and chitosan macromolecules charged progressively in their presence with evaporation-induced self-assembly, which results in highly ordered nanocrystalline narrow rectangle microparticles of thickness is ca. 15 nm that are made from interstratified layers of a new crystalline polymorph of chitosan with nanoplatelets. Its presence and structure is characterized by small/wide-angle X-ray scattering, scanning and transmission electron microscopy, microRaman spectroscopy. Crystalline polymorph can be separated easily. It is insoluble in water and organics that provide scope for its use in nanocomposites.