Curvature-Dependent Interfacial Dielectric Efficiencies of PDMS@SiO2 Nanocomposites

Using the ab initio molecular dynamics simulations, we demonstrate that the introduction of a trace amount of small-sized SiO2 nanoparticles into poly(dimethylsiloxane) can improve the interface polarization, leading to the enhanced static dielectric constant. It is shown that larger particles have higher polarization capability. When the particle size is large enough, the curvature effect disappears, and the increment of the static dielectric constant reaches the maximum, showing the same variation trend with surface tension. Compared to the static dielectric constant of bulk poly(dimethylsiloxane), the interfacial static dielectric constant can be increased by up to 35% as the particle size is 3.6 nm. However, the interfacial polarization in the normal direction is restricted and depressed. The negative effect is also obvious such that the interface charges are strongly trapped, leading to the enlarged dielectric loss. As a consequence, the actual energy conversion efficiency decreases. Although the defects can be partially compensated by exerting a high electric field, the composite strategy could not be the optimal choice for designing dielectric polymers with high energy conversion efficiency.