Role of interface in highly filled epoxy/BaTiO₃ nanocomposites. Part I-correlation between nanoparticle surface chemistry and nanocomposite dielectric property

The interface is critical for the design of polymer nanocomposites with desirable properties. The effect of interface behavior on the properties of polymer nanocomposites with low nanoparticle loading has been well documented. However, our understanding of the role of the interface in highly filled polymer nanocomposites is still limited because of the lack of comprehensive research work. In this contribution, by using BaTiO₃ nanoparticles with six kinds of surface chemistry, we have prepared highly filled epoxy nanocomposites (50 vol% nanoparticle loading). The role of nanoparticle surface chemistry on the dielectric properties of epoxy nanocomposites is investigated at a wide frequency and temperature range by using broadband dielectric spectroscopy. Combining the microstructure analysis of the highly filled nanocomposites with a comprehensive X-ray photoelectron spectroscopy characterization of the surface chemistry of the BaTiO₃ nanoparticles, an understanding is formed of the correlation between the nanoparticle surface chemistry and the dielectric properties of the nanocomposites. The functional group density, functional group type, and electrical properties of the modifier-the three parameters that are inherent from the nanoparticle surface modification-have a strong impact on the temperature and frequency dependence of the dielectric constant and dielectric loss tangent. This work demonstrates the great importance of surface chemistry in tuning the electrical properties of dielectric polymer nanocomposites.