Preparation and characterization of poly(vinyl- alcohol)/chitosan blends with ZnO nanoparticles

This research focuses on relating structure and mechanical properties of nanocomposites with antimicrobial activity. Organic nanoparticles of chitosan (CS) and inorganic nanoparticles of ZnO, both with cumulative antimicrobial activity, are added in a non-toxic poly(vinyl- alcohol) (PVA) matrix. CS reduces crystallinity of PVA inducing degradation of mechanical properties, but the properties of the polymer matrix can be improved by chemical crosslinking with glutaraldehyde (GA) and by adding ZnO nanoparticles. A solution of low molecular chitosan in dilute acetic acid was mixed with solution of fully hydrolyzed PVA at different weight ratios, by means of direct blend process. ZnO nanoparticles were synthesized by the precipitation method from ZnSO4·7H2O and added to PVA/CS blends. The resultant suspensions were casted and then dried in oven in order to obtain a thin flexible films. The structure of these mono-, bi- and ternary systems with different composition were characterized by means of dynamic mechanical analysis (DMA). The DMA analysis showed that CS reduces the crystallinity degree of PVA leading to a higher amount of the amorphous phase contributing to the α relaxation that corresponds to the glass to rubber transition. However, the mobility of the amorphous phase can be restricted with crosslinking. Moreover, ZnO NPs improve mechanical properties of the PVA/CS mixture and reduce the negative effect of CS on PVA properties.