Reduction of Dielectric Signal of the Interfacial Segmental Dynamics in Polymer Nanocomposites*

In this study we focus on polymer nanocomposites (PNCs) with dispersed silica core nanoparticles. We examine the dielectric strength and relaxation behavior of segmental dynamics in the interfacial polymer layer surrounding silica nanoparticles. The presented analysis reveals the significant drop in the dielectric strength, and its anomalous temperature dependence in polymer layer adsorbed to nanoparticles. We ascribe the observed effect to the restricted amplitude of segmental relaxation in the interfacial/adsorbed layer. The theoretical model explaining the unusual temperature dependence of dielectric strength is presented. Our results provide new view on discussion of dynamics in interfacial layer in PNC that may be applied to the thin polymer films as well: Not only characteristic time scale, but also amplitude of structural relaxation can be strongly affected by the presence of an interface.