Polyesterifcation of wood with sorbitol and citric acid seems to be a promising chemical wood modification technique that is both low-cost and produced from bio-based chemicals. An interesting aspect of the modification is the interaction of water with the polyesterified wood since the relationship with moisture appears to be unique compared to other wood modification systems. This communication paper presents preliminary results from trials assessing the effect of weight percentage gain (WPG) on swelling properties and water saturated low-field NMR (LFNMR) spectra. Bulking coefficients indicated that the sorbitol-citric acid polymer penetrated the cell wall and higher WPGs led to greater bulking coefficients. Surprisingly, anti-swelling efficiency decreased with increasing WPG. This was due to an increase in water saturated volume at high WPG which suggests the modification alters the structure of the cell wall in a way that allows it to swell beyond its original volume. LFNMR spectra showed the development of a new peak with increasing WPG which may be attributed to water associated with the hydrophilic sorbitol-citric acid polymer.

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