Small-angle neutron and x-ray scattering (SANS and SAXS) offer versatile tools for characterizing the structure of wood and other cellulose-based materials. The methods cover a spatial range roughly from 1 to 500 nm, thereby extending over multiple levels of wood's hierarchical structure. They are sensitive to the lateral dimensions and packing of cellulose microfibrils, as well as the presence of water in the nanoscale structure of wood. A major bottleneck for wider applicability of small-angle scattering in wood-related studies is the challenging data analysis, which is necessary to obtain quantitative results from the scattering data. As efficient x-ray and neutron sources are becoming increasingly available to non-specialist users, the development of a widely-applicable small-angle scattering data analysis method for wood and other plant cell wall materials is highly desired.<br/><br/>We used SANS and synchrotron-SAXS to characterize the nanoscale structure of Northern European wood species and developed an analytical model to interpret the data. The model is based on hexagonally packed cylinders and yields realistic numerical values for the microfibril diameter (2.6-2.9 nm) and their packing distance (3-4 nm in wet state). The capabilities of the method were demonstrated with never-dried and air-dried wood samples as well as an <i>in situ</i> SAXS measurement during drying. The model produced good agreement between SANS and SAXS data and reflected well the moisture-dependent changes in wood nanostructure even on a limited scattering vector range and using fitting in batch mode. In particular, the packing distance of the microfibrils decreased from 3-4 nm to below 3 nm during drying in room air. The presentation will discuss the potential of small-angle scattering methods in structural studies of wood and other cellulosic materials, highlighting the role of a proper analytical model that would enable high-throughput characterization of wood and cellulose nanostructure for various applications.

Small-angle scattering methods for efficient characterization of wood nanostructure and moisture behavior

255th National Meeting (2018)

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