Aqueous modification of waterlogged archaeological wood by phenylboronic acid to reduce hygroscopicity and improve the dimensional stability

During the dehydration of waterlogged archaeological wood (WAW), shrinkage inevitably occurs due to capillary force and hydrogen bond recombination as WAW loses free and adsorbed water. Existing drying techniques, including solvent displacement, freeze-drying, and supercritical fluid drying, only take effect by reducing or eliminating the surface tension of liquid. Nonetheless, the contribution of hydrogen bond recombination in shrinkage has long been neglected and a countermeasure concerning this problem is needed. In this study, we propose a simple aqueous phenylboronic acid (PBA) treatment that can help improve dimensional stability and reduce hygroscopicity of WAW. Analysis by Fourier transform infrared spectroscopy, density functional theory calculation and dynamic vapour sorption reveal that PBA can incorporate with hydroxyl groups (–OH) on cellulose through coordination and hydrogen bonds, occupy the water-cellulose binding sites, and possibly inhibit the formation of hydrogen bonds between adjacent cellulose chains.