Water accessibility to hydroxyls confined in solid wood cell walls

The hydrophilicity of wood cell walls derives from the presence of hydroxyls, but their accessibility is restricted by physical confinement from the stiff, solid cell walls. This study examines how this confinement affects water uptake of the accessible hydroxyls by tuning their amount through replacement with various non-hydrophilic functional groups. Results from gravimetrically determined hydroxyl accessibility by deuterium exchange are shown not to correlate with moisture uptake in cell walls under vapour conditions or at water-saturation. Instead, spatial availability for water inside solid cell walls is suggested as the dominant factor in controlling cell wall moisture uptake at given climatic conditions.