Dielectric response in epoxy nanocomposites incorporating various nano-silica architectures

The molecular dynamics and physical mechanisms in dielectric nanocomposites are key to develop materials with tailored properties. The effect of the architecture of nanoparticles on the bulk properties is one such factor which needs to be studied and understood. The aim of this study is to investigate the effect of different core-shell structures on the bulk properties of the epoxy nanocomposites. TEM images confirm the successful synthesis of the core-shell and hollow nanoparticles. Epoxy nanocomposites filled with three types of nano-silica architectures, namely core (SiO2), core-shell (SiO2-SiO2) and hollow (h-SiO2) were prepared. They were characterised via broadband dielectric spectroscopy as a function of frequency in the range of 10-1-105 Hz and a temperature range of -160°C - 160°C. Besides well known relaxations, an additional so called SiOH relaxation is observed. Its intensity is proportional to the amorphous content of the nanoparticles. A distinct overlap between the epoxy β relaxation and SiOH relaxation is also observed, significantly affecting the intensity of the β relaxation. Finally, due to the presence of additional core-shell interface in case of SiO2-SiO2 filled nanocomposite two interfacial polarization peaks are observed. These preliminary findings illustrate noticeable effect of the architecture (additional interfacial polarization peak) and crystallinity (SiOH relaxation) of the nanoparticles on the dielectric behaviour of the nanocomposite.