Three-dimensional alignment of cellulose II microcrystals under a strong magnetic field

Abstract

In this study, enzymatic synthesis was conducted using cellodextrin phosphorylase (CDP), sucrose phosphorylase (SP), and sucrose with 1-azido-1-deoxy-β-glucoside (β-glucosyl azide) as the acceptor in phosphate buffer at pH 7.0. This yielded cellulose oligomers (degree of polymerization, DP ≈ 10) with azido groups at the reducing end as a white precipitate. A suspension of cellulose microcrystals with exposed azido groups on the surface was obtained via dissolution and recrystallization of the synthetic products dispersed in water by heating. The flat, ribbon-like cellulose microcrystals were a crystalline form of cellulose II and were several micrometers in length and several hundred nanometers in width. The microcrystals were 5.1–5.2 nm thick, which is equivalent to the chain length of cellulose oligomers with DP ≈ 10. When the cellulose II microcrystal suspensions were dried under a horizontal static magnetic field of 8 T, oriented films were obtained, wherein the microcrystals were aligned three-dimensionally. Synchrotron X-ray diffraction studies of the films revealed that the easy and intermediate axes (χ₁ and χ₂, respectively) of the cellulose II crystals corresponded approximately to the [1 1 0] and [1 ̅₁ 0] directions, respectively.