Effect of an ionic liquid on the physicochemical properties of chitosan/poly(vinyl alcohol) mixtures

Mixtures containing two polymers, chitosan (Ch) and poly(vinyl alcohol) (PVA) as well as mixtures with addition of an ionic liquid (IL) 1-butyl-3-methyl-imidazolium chloride (BMIM⁺Cl^-) were prepared via casting from aqueous solutions. The morphology, mechanical and surface properties of Ch/PVA mixture films were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), infrared spectroscopy (ATR-FTIR), contact angle measurements and tensile tests. Rheological studies were performed via solutions of pure polymers and their mixtures with and without the addition of an ionic liquid. The viscosity curves of mixtures were found to lie between those of pure components over the entire compositional range. The non-Newtonian index (n) of these mixtures were determined by the power law model indicating shear-thinning behavior with pseudoplasticity increasing with an increasing weight fraction of chitosan. Results obtained from SEM, AFM, contact angle measurements, TGA and infrared spectroscopy (ATR-FTIR) were compared and showed that the addition of an ionic liquid is beneficial to the formation of intermolecular forces and the network structure between the polymer and mixture films, which leads to an improvement in the properties of these materials.