Three-Dimensional Magnetic Alignment of Cellulose II Microcrystals for Elucidating Their Hydrogen-Bonding Network and Anisotropic Mechanical Properties

This study establishes a comprehensive platform for the axis-resolved analysis of anisotropic structure−property relationships in cellulose II. Using plate-like microcrystals synthesized via enzymatic polymerization, three-dimensionally oriented composite films were fabricated by combining a substrate-induced flat-on orientation with high-field magnetic alignment. X-ray diffraction revealed a highly ordered structure where the molecular chain axis (c-axis) is perpendicular to the substrate, and the [110] direction is aligned with the magnetic field. The type-B hydrogen-bonding network was indicated as a plausible structure for cellulose II upon integrating polarized Fourier transform infrared spectroscopy with geometrical analysis based on structural models. Mechanical testing combined with rule-of-mixtures analysis yielded an apparent modulus of 16.28 GPa along the magnetically selected χ1 direction, comparable to the crystal modulus of 17.8 GPa calculated from the elastic tensor. This methodology provides a powerful approach for elucidating the structural and mechanical anisotropies of lamellar polymer crystals beyond cellulose.