Scattering Methods for Characterizing Cellulosic Materials

Y. Mao
University of Maryland,
United States

Summary:

Neutron and X-ray scattering techniques are powerful tools for structural characterization of materials. Instrumental configurations can be set in a scattering experiment to perform wide- and small-angle scattering, exploring multi-scale structures, ranging from crystal structures at the atomic level, to nanostructures with a characteristic length of up to approximately 100 nm. Scattering characterization can be done non-invasively. In addition, researchers may benefit from a complementary use of both neutron and X-ray scattering, taking advantage of the difference in scattering contrast in these techniques. Of particular interest is the investigation of multi-component systems, such as composites, polymer blends, alloys, etc. The working principles of small-angle neutron and X-ray scattering (SAXS/SANS) as well as wide-angle X-ray diffraction (WAXD) are outlined. Three examples are given, with the focus being on cellulosic material characterization, to demonstrate their applicability. In the first example, a study on multi-component cellulose solutions using SANS is discussed. Using selective isotope labeling, nanoscale structures in concentrated solutions can be investigated using SANS. Next SAXS and WAXD characterization of hierarchical structures in engineered wood is presented. The top-down nanofabrication allows developing novel wood-based materials utilizing the inherent mesoporous and aligned structures in natural wood. SAXS and WAXD employing a 2D detector is particularly useful in deciphering the multi-scale structures showing preferred orientation. Third, the crystal structure determination of cellulose-based, metal-coordinated open framework structure using WAXD is discussed. The transition metal-engineered cellulose crystals show intriguing ion transport properties which is linked to the unique directional 1D channels. Establishing structure-property relationships is emphasized in all three examples.