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

Abstract

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.