Local mechanical and dielectric behavior of the interacting polymer layer in silica nano-particles filled SBR by means of AFM-based methods

Filler-polymer interactions in reinforced rubbers are mainly governed by a thin layer of polymer around the filler particles. The dynamics of this layer has long been a matter of intense investigation. Some researchers suggest that this “interacting layer” is immobilized and possesses slower dynamics compared to the bulk, whereas some others consider it equally mobile. In this work, we address this problem by studying the macroscopic characteristics of reinforced rubber using Broadband Dielectric Spectroscopy (BDS) and by measuring its local dielectric behavior using a new AFM based approach: nano-dielectric spectroscopy. This new approach enables us to study the dielectric response of the interacting polymer layer and the bulk dynamics locally, with a spatial resolution of about 20–30 nm. The total amount of interacting polymer within the compounds was also obtained by analyzing the local mechanical properties. Both macro- and nano-measurements show no differences in the polymer local dynamics for the compounds here analyzed. We propose that, for our particular system, the interacting polymer layer shares the same local relaxation dynamics with the bulk rubber due to the presence of a flexible link between the polymer chains and the nanoparticles.