Preparation and dielectric properties of core–shell structured Ag@polydopamine/poly(vinylidene fluoride) composites

Ag nanoparticles@polydopamine (AgNPs@PDA) core–shell particles were prepared by one-step oxidative–reductive reaction, which Ag + was used as oxidant and dopamine as reducing agent. The dopamine was polymerized to PDA surface and shielded the Ag nanoparticles . The AgNPs@PDA particles were used as fillers and introduced into poly(vinylidene difluoride) (PVDF) to prepare the AgNPs@PDA/PVDF dielectric composites. AgNPs were introduced aiming to increase the dielectric constant of the composites and PDA was employed to improve the compatibility between fillers and polymer. The morphology and the dielectric properties of the AgNPs@PDA/PVDF composite films were thoroughly investigated. The influencing factors to the dielectric performances of the composites were studied, including the ratio of AgNO 3 and dopamine, pH values of the preparing solution and the fraction of the fillers. The highest dielectric constant of the AgNPs@PDA/PVDF composites was about 53 when the content of fillers was 25   wt.% at 100   Hz. The percolation threshold of the composites was predicted at about 25.5   wt.%.