Fabrication of enhanced dielectric PVDF nanocomposite based on the conjugated synergistic effect of ionic liquid and graphene

Abstract

In recent years, due to its excellent dielectric property in polymers, polyvinylidene fluoride (PVDF) has been widely used to prepare polymer based electrical device and manufacture flexible sensors, transducers and energy harvesters. However, compared with some inorganic materials, the finite dielectric property of PVDF still limited its application as piezoelectric material in high-sensitivity pressure sensors for detecting dynamic signals. In this report, we prepared a high dielectric flexible material based on PVDF compositing with graphene and ionic liquid (IL, 1-butyl-3-methylimidazolium hexafluorophosphate). The introduction of IL improves the dispersion of graphene in nanocomposite matrix, and the conjugated synergistic effect of IL and graphene enhance the dielectric property of PVDF nanocomposite. IL can help to improve the interfacial polarization effect between graphene and PVDF matrix, and increase the content of β phase due to the ion-dipolar interaction between the -CF2 of the polymer backbone and imidazolium cation. Meanwhile, the uniform dispersion of graphene in PVDF can promote the formation of tiny graphene microcapacitor structure in matrix, which is significant in improvement of dielectric and electrical properties of PVDF nanocomposite. The nanocomposite with the concentration of 2.0 wt% graphene and 2.0 wt% ionic liquid has the best dielectric property in our work, the dielectric constant of nanocomposite is nearly 6 times higher than that of pure PVDF. In addition, the dielectric loss is less than 0.2 when the frequency between 104-106Hz, which is acceptable in applications.