Flavonoid Insertion into
Cell Walls Improves Wood
Properties
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Abstract
Wood has an excellent mechanical performance, but wider
utilization
of this renewable resource as an engineering material is limited by
unfavorable properties such as low dimensional stability upon moisture
changes and a low durability. However, some wood species are known
to produce a wood of higher quality by inserting mainly phenolic substances
in the already formed cell walls – a process so-called heartwood
formation. In the present study, we used the heartwood formation in
black locust (<i>Robinia pseudoacacia</i>) as a source of
bioinspiration and transferred principles of the modification in order
to improve spruce wood properties (<i>Picea abies</i>) by
a chemical treatment with commercially available flavonoids. We were
able to effectively insert hydrophobic flavonoids in the cell wall
after a tosylation treatment for activation. The chemical treatment
reduced the water uptake of the wood cell walls and increased the
dimensional stability of the bulk spruce wood. Further analysis of
the chemical interaction of the flavonoid with the structural cell
wall components revealed the basic principle of this bioinspired modification.
Contrary to established modification treatments, which mainly address
the hydroxyl groups of the carbohydrates with hydrophilic substances,
the hydrophobic flavonoids are effective by a physical bulking in
the cell wall most probably stabilized by π–π interactions.
A biomimetic transfer of the underlying principle may lead to alternative
cell wall modification procedures and improve the performance of wood
as an engineering material