Improved dielectric properties of Ag@TiO2/PVDF nanocomposites induced by interfacial polarization and modifiers with different carbon chain lengths

Abstract

In this study, poly(vinylidene fluoride) (PVDF)-based nanocomposites filled with surface-functionalized Ag@TiO2 core-shell nanoparticles were fabricated in order to achieve high dielectric permittivities. Using two phosphonic acid surfactants with differing carbon chain lengths, octyl and octadecyl phosphonic acid, the filler surfaces were modified to improve the dispersion of the core-shell filler in PVDF. The experimental results showed that the dielectric constant of the composite with fillers modified using octyl phosphonic acid (148 at 1 kHz) was almost three times that of the material with fillers modified using octadecyl phosphonic acid (58 at 1 kHz) at the same filler loading. The mechanisms of interfacial polarization between the modified core-shell filler and the polymer matrix were analyzed by introducing a circuit model based on AC impedance spectroscopy.