Wood is susceptible to fungal degradation, but the susceptibility can be reduced by a range of non-toxic wood modification methods. The mechanisms responsible for the protective effect are not entirely clear, but are for some methods known to be related to a reduced moisture content in the wood cell walls. To explore how different wood modifications function is interesting <i>per se</i>, and it is also helpful when designing novel wood modification systems aimed at simplifying process set-ups or reducing modification costs.<br/>Acetylation is one of the most well-known non-toxic wood modification methods. During acetylation, wood is impregnated with acetic anhydride and thereafter cured. This causes part of the hydroxyl groups of the cell wall biopolymers to be replaced by acetyl groups. By tuning the acetylation protocol, samples with different spatial distribution of acetylation within cell walls can be designed and their interactions with water and fungi studied. This is helpful when trying to understand how and where modification is needed to prevent fungal degradation, and which role the content and location of moisture plays in this. Raman microscopy offers spatially resolved chemical information at the scale needed for this endeavor. In the present study, Raman microscopy data were used to document that Norway spruce wood specimens with different acetylation profiles could be produced by varying the acetylation conditions. The conditions were varied by omitting or allowing the xylem tissue to swell in pyridine during acetylation, and by regulating the time and temperature of the impregnation step. In this way, acetylation was achieved of either the whole cell wall or only part of it, i.e. of the cell wall lumen surface. In addition, the amount and location of water within the differently acetylated wood specimens was studied using Raman microscopy as well as by Low-Field Nuclear Magnetic Resonance (LFNMR) relaxometry and sorption balance techniques. Results show that acetylation successfully excluded moisture where acetyl groups were found in the cell wall, and that the different acetylation protocols also affect LFNMR spin-spin relaxation times and water population sizes as expected. The method developed will be useful when studying the role of water for the susceptibility of wood to fungal degradation.

Mapping targeted acetylation of Norway spruce wood by use of Raman microscopy

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.