The isotopic effect of deuteration on the conductive properties of chitosan films

Abstract Chitosan biopolymer has gained attention due to its distinctive chemical and environmental characteristics, such as its biocompatibility and biodegradability, ability to form fibres/films, and ionic conductivity. Its functional groups offer various interactions, including cross-linking, intermolecular hydrogen bonding, complex formation, and chelation. All this makes chitosan one of the most extensively used platforms for developing biomedical and pharmaceutical applications, agriculture, water treatment, environmental protection, energy storage systems and many others. This study examined the structure and properties of protonated and partially deuterated chitosan films. Herein, we present the chitosan films prepared from their acidic solutions by casting. By employing spectroscopic techniques, it was shown that, firstly, there is a partial deuteration of chitosan polymer films; secondly, the higher the content of D2O used for deuteration, the lower the conductivity of CS films, thus, the more apparent kinetic isotope effect arising from hydrogen-deuterium exchange in the polymer structure. The conductive properties were evaluated by using chronoamperometry and a four-probe approach. This work provides a simple way to shed light on the probable semi-classical nature of the mechanism underlying the conductive properties of chitosan.