Interface engineering of ionic liquid integrated graphene in poly(vinylidene fluoride) matrix yielding magnificent improvement in mechanical, electrical and dielectric properties

Graphene oxide(GO) functionalized with imidazolium ionic liquid(IL) is characterized from spectroscopic and microscopic techniques. Poly(vinylidene fluoride)(PVDF)/ionic liquid functionalized graphene oxide(GO-IL) composite(PGL) films are flexible, and exhibit fibrillar network morphology. Transmission electron microscopy indicates dendritic morphology at 3%(w/w) GO-IL and the formation of piezoelectric beta-polymorph PVDF is evidenced from wide angle x-ray scattering. PGL composites exhibit a gradual increase of melting, crystallization, glass transition (T-g) and other relaxation temperatures with increasing GO-IL concentration. The maximum increases of storage modulus (73%), Young's modulus (333%) and tensile strength (628%) occur at 3% filler concentration. Halpin-Tsai equation suggests GO sheets are randomly distributed at low GO-IL concentration but they are unidirectional at higher concentration. A sharp increase of dc-conductivity of PGL composite to similar to 10(-2) S/cm occurs with a percolation threshold of 0.1% (w/w). The dielectric permittivity increases from 7.5 for PVDF to 13.5 for 3% filler with a percolation threshold at 0.1% (w/w) filler. (C) 2015 Elsevier Ltd. All rights reserved.