Competing Self-Assembly to Access Helical Chitin Nanofibers for Advanced Chitinous Materials

Self-assembly affords a rich design space in fabricating polymeric nanomaterials. However, the crystalline polymer often exhibits the vigorous self-assembly process due to the extensive inter- and intra-molecular interactions, leading to the challenge in controlling their self-assembly behavior at the nanoscale. Herein, this work proposes a competing self-assembly strategy to regulate the molecular self-assembly tendency of chitin (a semi-crystalline polysaccharide) for achieving the regenerated chitin nanofibers with helical structure. This approach focuses on subtly modulating the noncovalent interactions among the chitin chains through deacetylation in a homogeneous system. By fine-tuning the degree of deacetylation (DD) to a moderate level (≈26%–37%), this work facilitates the chitin chains to compete self-assembling into the α-chitin and hydrated chitosan crystalline structure, which effectively mitigates the overall self-assembly tendency of the chitin chains and ultimately restricting their aggregations to nanoscale dimensions. This fabrication concept achieves various chitin nanofibers morphology (single, randomly branched and comb-like), all featuring a helical configuration. The chitin nanofibers are successfully processed into the nanopaper and bioink, highlighting the potential in constructing high-performance materials. This work anticipates that the competing self-assembly concept can be extended to other crystalline polymers with strong molecular interactions, offering a new pathway to design advanced nanomaterials for diverse applications.