Zn2+-Driven Crystalline Reorganization Enables Strong and Thermally Stable Tunicate Cellulose Filaments

초록

Tunicate-derived cellulose nanofibers (CNFs) exhibit exceptional intrinsic mechanical properties; however, translating these attributes to macroscale fibers remains challenging because dense packing and long-range alignment are difficult to achieve. Here, we report a coordination-driven assembly of 2,2,6,6-tetramethylpiperidine-1-oxyl-oxidized CNFs using multivalent metal cations (Ca2+, Cu2+, Zn2+, Fe3+, and Al3+) to direct microstructural evolution. We find that specific coordination chemistries trigger pronounced structural reorganization; notably, Zn2+ induces a phase transformation in which native cellulose I beta crystallinity is replaced by a robust metal-coordinated network. This transformation produces filaments with outstanding mechanical performance, achieving a tensile strength of 581.8 +/- 29.4 MPa and a Young's modulus of 18.8 +/- 3.3 GPa, exceeding previously reported metal-ion-crosslinked cellulose composites. Coordination further enhances thermal stability, increasing the onset degradation temperature by up to 48.6 degrees C. These results establish a direct link between ionic coordination and crystalline restructuring, providing a scalable route to strong, heat-resistant, and sustainable structural fibers.

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