Changes in water vapour uptake ability of xylan derivatives monitored by QCM-D humidity module

In surface science, model surfaces of small amounts of chemically defined compound are deposited on a flat surface by means of e.g. spincoating technique. The model surface approach enables the investigations of the direct surface interactions on the molecular level since it enables efficient and well-established use of the surface analytical techniques such as quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). The resistance to humidity, swelling behaviour and the ability to uptake water vapour are features which are strongly related to the behaviour wood and agro-derived polymers in different applications such as in film and membranes. These features have a direct link also to the mechanical and thermal properties and therefore they need to be fully understood and controlled when the aim is to prepare biobased materials which are effectively functioning also at higher humidities. In this work the changes in the water vapour uptake and swelling behaviour of the xylan derivatives were studied using the model film approach. Model films were prepared using the different crosslinking xylan derivatives. The water va-pour uptake of the thin xylan model films was monitored using QCM-D humidity module. With the QCM-D, the mass uptake due to the water vapour binding was defined. Simultaneously the changes in the viscoelastic properties of the cross-linking xylan when subjected to different relative humidity conditions were de-termined. Clear changes in the water uptake ability were taking place before and after crosslinking of the films.