Analytical description of the scattering of cellulose nanocrystals in tracheid wood cells

Abstract

Tracheid cells are complex structures. The cellulose nanocrystals are wound in helices around the tracheid cell axis. The microfibril angle describes the angle between the cellulose crystals and the cell axis. Furthermore, the cross-sectional shape of tracheids varies widely, ranging from square to round. These parameters affect the scattering geometry and thus the experimental scattering signal. In an experiment, the macroscopic sample orientation relative to the beam is a further variable. Here, a description is presented that allows the calculation of azimuthal scattering patterns for any hkl reflection from cellulose nanocrystals in tracheid cells of any orientation. Additionally, this model can be used to describe fibrillar aggregates with an additional level of organization that surpasses an ideal fiber texture, for example pairs of twisted fibers.