Features of the Structural Organization and Sorption Properties of Cellulose

Abstract

An improved model of the layered structure of cellulose microfibrils is proposed, taking into account the presence of slit-like pores between its structural elements. The scheme of the formation of donoracceptor intramolecular, intermolecular and interlayer hydrogen bonds of one glucopyranose unit in the cellulose crystallite is presented. The mechanism of specific adsorption interactions of water molecules in a monolayer with active centers located on the hydrophilic surfaces of elementary fibrils is described. The energy of dipole-dipole interactions was calculated depending on the distance between the active center and the adsorbate water molecule. The thermodynamic parameters characterizing the state of the adsorbate in the adsorption layers are determined by the proton magnetic relaxation method and sorption measurements. The possibility of determining the net heat of adsorption in a bilayer taking into account the Arrhenius nature of the correlation times of the thermal molecular motions of the adsorbate was established. An increase in the entropy of adsorbed water during the adsorption process was revealed. It was found that during adsorption, a part of the inner regions of crystallites transitions to their surface with the participation of cellulose hydroxyl groups, and during desorption, the reverse process is observed.