Determination of Interphase Thickness in Silicone Nanocomposites from Dielectric Properties

The material properties of polymeric nanocomposites can be modified significantly by the characteristics of the interfacial zone between the polymer and the nanoparticles. The present study analyzes the dielectric response in order to investigate the intermolecular interactions in the interphase at the boundary layer and to quantify them. For this purpose, crosslinked nanocomposites based on polydimethysiloxane and silica nanoparticles with different surface modifications (hydrophilic, hydrophobic) were produced. In the dielectric spectrum of the nanocomposites an additional relaxation is identified that is attributed to the interphase. The volume fraction of this interphase is determined from the dielectric decrement of its relaxation. Moreover, from three-dimensional transmission electron microscopy images, the three-dimensional distribution and the specific surface of the nanofiller is determined. By combining the specific surface with the result for the volume fraction of the interphase, the thickness of the interphase is calculated.