On the organization of hemicelluloses in the wood cell wall

The structural arrangement of the polymers in the cell wall of wood has still not been fully established. This relates specifically to the role of the two hemicelluloses, glucomannan and xylan, in the secondary cell wall. In softwoods there is a good consensus with regard to the glucomannan as associated with the cellulose microfibrils while the role of the xylan has been more questioned. Recent NMR-studies have now strongly indicated a close association of xylan also to the cellulose microfibrils in softwoods. In order to assess these findings, studies utilizing complementary techniques are here re-examined in order to scrutinize these results. By analyzing results from polymer orientation (polarized FTIR), molecular blending (dynamic mechanical analysis), polymer interaction (dynamic FTIR) and moisture induced swelling (synchrotron X-ray) a close association of xylan to cellulose is here fully supported. Thus, the overall results from all multiple techniques strongly advocate an association of both glucomannan and xylan to the cellulose microfibrils and aggregates while the lignin is considered as encompassing the remaining space between the undulating cellulose/hemicellulose aggregate structures and acting as an independent polymer entity.