Anisotropic Elastic Properties of Cellulose Measured Using Inelastic X-ray Scattering

Abstract

Plant fibers such as linen are remarkably stiff materials in the longitudinal direction of the fiber. As plant cell walls are composites made of cellulose nanocrystals, the so-called microfibrils, embedded in a disordered matrix, those nanocrystals should exhibit an even higher elastic modulus G . We have determined the elastic properties of cellulose microfibrils via the sound velocities measured by inelastic X-ray scattering (IXS). The IXS technique is particularly sensitive to crystal properties by discriminating the contribution of disordered material. A strong anisotropy is observed, with a much lower elastic modulus perpendicular to the fiber direction ( G 1 = 15 GPa) than parallel to it ( G 2 = 220 GPa). The latter modulus is considerably higher than all values previously determined and will have a significant impact on models for the elastic properties of cellulose microfibrils and of composites based on them.