Structural and mechanical roles of wood polymer assemblies in softwood revealed by gradual removal of polysaccharides or lignin

Abstract

A deep understanding of the inherent roles of wood polymers such as cellulose, hemicelluloses, and lignin in the hierarchical structure of wood is of key importance for advancing functional wood-based materials but is currently lacking. To address this gap, we clarified the underexplored contributions of wood polymer assemblies to the structural support and compressive properties of wood by chemically removing polysaccharides or lignin from wood blocks of a conifer Cryptomeria japonica. Compositional and structural evaluations revealed that cellulose, hemicelluloses, and lignin contributed to the dimensional stability of wood, especially that the polysaccharide network at cell corners sustained the honeycomb cell structure. Wood polymer assemblies featuring the anatomical structure of wood were also evaluated in terms of compressive properties. The modulus and strength reflected the density and anisotropy, whereas fracture behavior was well characterized by each wood polymer assembly through the classification of stress–strain curves based on principal component analysis. The difference in fracture behaviors indicated that the rigid lignin and flexible cellulose assemblies, possibly mediated by hemicelluloses, complementarily determine the unique compressive response of wood. These findings enable the adjustment of wood functionality and the selection of composite components for wood modification while inspiring the development of novel wood applications.