Chitosan-derived molecular films self-assembled on the gold surface were characterized using electrochemical methods combined with quartz crystal microbalance, atomic force microscopy and surface enhanced infrared absorption spectroscopy. We have observed potential-dependent structural transitions, which involved a reorientation of the oligosaccharide molecules and either depletion or accumulation of water molecules within the film. The nature of water accumulated within the chitosan-derived film varies with the potential but it is dominated by hydrogen-bonded species. The content of water entrapped within the oligosaccharide film can be controlled by the potential applied to the electrode, which means that its hydration/dehydration can be triggered by an electric field. (C) 2019 Elsevier Ltd. All rights reserved.