Chitosan as a Versatile Biopolymer Platform for Functional Materials

Chitosan, a polysaccharide derived from the deacetylation of naturally abundant chitin, has emerged as a foundational biopolymer for functional materials due to its unique properties, including antibacterial activity, biocompatibility, and flame retardancy. Furthermore, chitosan can self-assemble into chiral nematic (cholesteric) liquid crystals (LCs) when suspended in strongly hydrogen-bonding acidic solvents, showcasing selective reflectivity and circular dichroism in the infrared portion of the electromagnetic spectrum. Despite these promising characteristics and their relevance to a wide range of industrial and biomedical applications, the influence of chitosan’s molecular structure on its final properties remains underexplored. This hinders the deterministic design of relevant solution processing routes and final functional materials with tailored mechanical, optical, and interfacial properties. In this talk, we will discuss our recent advances in establishing structure-property relationships in chitosan solutions, elucidating its phase behavior and LC self-assembly. Combining theoretical frameworks, such as Flory-Huggins and Landau-De Gennes theories, with experimental investigation of phase behavior and inter/intra-molecular interaction by spectroscopy methods (e.g. Fourier-transform infrared spectroscopy, X-ray diffraction), we uncovered the dependence of long-range order formation on polymer chain interactions and macromolecular mobility. Specifically, we will highlight our effort in quantifying the impact of degree of deacetylation and molecular weight on chitosan phase behavior and discuss how we have leveraged chemical modification to further tailor solubility and final optical, mechanical, and interfacial properties. Last, we will discuss how we have used these relationships in the context of designing functional chitosan-based materials for a broad range of applications, from optical coating to biodegradable food packaging and textile recycling.