Deacetylation mediated non-covalent assembly for regulating sol-gel behavior of chitin-NaOH solution

The development of high-performance chitin-based materials regenerated from solutions is fundamentally constrained by the insufficient mechanistic understanding of how the degree of deacetylation (DD) governs molecular interactions, self-assembly pathways, and resultant hierarchical architectures. Herein, we systematically investigate the DD-dependent solution and gelation properties of chitin homogeneous systems, followed by unveiling the molecular interaction-induced self-assembly mechanisms that precisely regulate gels aggregation structures and mechanical properties. Competitive non-covalent interactions‑hydrogen bonding versus hydrophobic forces (modulated by DD)-orchestrate distinct molecular assembly modes, yielding tunable gels morphologies and properties. At low DD, hydrophobic dominance triggers rapid phase-separated gelation, forming mechanically weak gels with macroporous architectures. Intermediate DD establishes relative equilibria between hydrophilic/hydrophobic interactions, enabling a weak non-covalent network of solution with a low viscosity and a high gelation temperature, which result in relatively loose aggregated structures within gels and compromised mechanical properties. At high DD, hydrogen bonds-directed chains self-assembly prevails, fostering dense non-covalent networks and crystalline structures of gels that exhibit excellent mechanical properties. Deep insights of the gelation behavior of chitin solutions will fill in the gaps of chitin research, further revealing the self-assembly behavior of chains and aggregated structure of gels, which enable to manipulate the properties of chitin-based hydrogels accurately.