Adsorption and viscoelastic properties of cationic xylan on cellulose film using QCM-D

The adsorption and viscoelastic properties of cationic xylan layers adsorbed from an aqueous electrolyte solution (NaCl 0, 1, 10, 100 mM) on a cellulose model surface were studied using quartz crystal microbalance with dissipation (QCM-D). Three cationic xylans with different charge densities were used (molecular weight, 9,600 g/mol with degrees of substitution, DS = 0.150, 0.191, and 0.259). The influences of the electrolyte concentration and charge density of cationic xylan on its adsorption onto a cellulose surface were investigated. Low charged cationic xylan was substantially more efficient in surface adsorption on cellulose compared to high charged cationic xylan at a low concentration of electrolytes. Adsorption of low charged cationic xylan decreased with increases in electrolyte concentration. However, adsorption of high cationic xylan increased with electrolyte concentration. The conformation and viscoelastic properties of the layers were interpreted by modeling the data under the assumption that the layers can be explained by the a Voigt model. Low charged cationic xylan adsorbed relatively weakly onto the cellulose surface, and formed a thicker, softer layer than high charged cationic xylan. On the other hand, high charged cationic xylan formed a thinner adsorption layer onto the cellulose surface.