Electrically variable interfaces in polymer nanocomposite dielectrics

Polymer nanocomposites generally exhibit unexpected dielectric/electrical performance far beyond the sum of every component, which is mainly due to the interface effect induced by the differences in structures and properties between the nanofillers and the polymer matrix. However, understanding the capricious interface effect in different polymer nanocomposites remains a major challenge. Here, we perform density functional theory calculations to investigate the atomic/molecular configurations and local charge behaviors of heterogeneous interfaces between the fillers of perovskites, oxides, two-dimensional materials, and polar/nonpolar polymers. Our findings demonstrate that atomic reconfiguration takes place during the formation of the inorganic/organic interface in order to minimize the overall energy of the system. Significant charge accumulation occurs at heterogeneous interfaces due to electron redistribution, especially for the examples of HfO2 and negatively charged Ca2Nb3O10. When applying an electric field, local polarization, especially around the interface, will be distorted and enhanced as a result of interfacial interaction. Even for the nonpolar polymer with linear dielectric oxides such as TiO2, induced dipole moments also appear near the interface, leading to the improvement of overall polarizability. The outcomes of our study verify that the variable electrical behaviors at the interfaces are highly dependent on the feature of every component constituting the inorganic/organic interface, which offers valuable insights for optimizing the experimental design of heterogeneous interfaces in polymer nanocomposites.