Miscibility studies on carboxymethyl chitosan and poly(N-vinylpyrrolidone) mixtures

The production of polymer mixtures is a widely used method to improve polymer performance, as such mixtures can combine advantageous properties from each component. In this study, mixtures based on carboxymethyl chitosan (CMCh) and poly(N-vinylpyrrolidone) (PVP) were characterized using steady shear measurements, viscometry, infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and atomic force microscopy. Viscometry and steady shear studies were performed on solutions of the native polymers and their mixtures with various weight proportions (80/20, 50/50, and 20/80%w/w). The rheological tests revealed that the apparent viscosity of solutions of CMCh/PVP mixtures was higher than that of the native polymer solutions. The rheological data showed that CMCh solutions and their mixtures were typical pseudoplastic liquids, which could be accurately described by the Cross and power law models. Viscometric parameters were determined using the method proposed by Garcia et al., which indicated good miscibility between CMCh and PVP in aqueous solution. Furthermore, the morphology, structure, and thermal properties of CMCh films changed when PVP was added. The obtained analytical data showed the formation of stable mixtures of CMCh and PVP, with a high miscibility ratio between these polymers, through intermolecular interactions between the polymer chains.