Silica fillers for enhancement of dielectric properties of poly(vinylidene fluoride) and its copolymer

Abstract

Poly(vinylidene fluoride) (PVDF) based polymers are known to exhibit outstanding piezo-, pyro-, ferro-, and dielectric properties owing to their structural β-phase. In this work, the prospect of enhancement of dielectric properties of PVDF and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-hfp) polymers has been explored by increasing their β-phase through incorporation of porous and non-porous silica nanoparticles. Polymer films, both in pure and nanocomposite forms, were prepared using a simple solution casting technique. FTIR-ATR spectroscopic analyses of the films revealed increased proportion of β-phase in the polymer nanocomposite films containing silica nanoparticles, compared to the pure polymer films. X-ray diffraction analysis also confirmed a higher β- to α-ratio in nanocomposite films than in pure films. The transformation is considered to occur due to interaction between surface of negatively charged silica nanoparticles and –CH2 group of the polymer which has a positive charge density. Electrochemical impedance spectroscopic measurements corresponded with the increased β- to α-ratio, as the nanocomposite films exhibited higher dielectric constant than the pure films. Mesoporous silica incorporated films even showed higher β- to α-ratio and dielectric constant than non-porous silica incorporated films which may be brought about by the presence of pores in the nanoparticles, which increases the surface area available for interaction with the polymers as well as provides a confined environment favouring the interaction. Thus, this work suggests the possible benefit of silica fillers in preparing nanocomposites of PVDF and its copolymer with enhanced dielectric properties, to be employed in the development of smart materials and in various other applications.