Dynamic mechanical and dielectrical properties of poly(vinyl alcohol) and poly(vinyl alcohol)-based nanocomposites

In this article we report on the investigation of the dynamics of poly(vinyl alcohol) (PVA) and PVA-based composite films by means of dielectric spectroscopy and dynamic mechanical thermal analysis. Once the characterization of pure PVA was done, we studied the effect of a nanostructured magnetic filler (nanosized CoFe2O4 particles homogeneously dispersed within a sulfonated polystyrene matrix) on the dynamics of PVA. Our results suggest that the a-relaxation process, corresponding to the glass transition of PVA, is affected by the filler. The glass-transition temperature of PVA increases with filler content up to compositions of around 10 wt %, probably as a result of polymer-filler interactions that reduce the polymer chain mobility. For filler contents higher than 10 wt %, the glass-transition temperature of PVA decreases as a result of the absorption of water that causes a plasticizing effect. The beta- and gamma -relaxation processes of PVA are not affected by the filler as stated from both dynamic mechanical thermal analysis and dielectric spectroscopy. Nevertheless, both relaxation processes are greatly affected by the moisture content. (C) 2001 John Wiley & Sons, Inc.