Improved dielectric properties of PVDF nanocomposites: a comparative study of noncovalent and covalent functionalization of MWCNTs

Polyvinylidene fluoride (PVDF) based nanocomposites with γ-oxo-pyrenebutyric acid-noncovalent modified multiwalled carbon nanotubes (denoted as PACNTs) and stearic acid-covalent modified MWCNTs (SACNTs) as nanofillers, were fabricated using solution-blending method and their dielectric properties were carefully investigated. γ-Oxo-pyrenebutyric acid (PA) or stearic acid (SA) can improve the dispersion of MWCNTs in PVDF matrix because of strong physical π–π interaction and the surface of MWCNTs grafted with SA respectively. The values of percolation threshold for PVDF/PACNTs and PVDF/SACNTs were determined to be 5.7 and 6.3 vol%, respectively. Higher dielectric permittivity and lower loss tangent of PVDF/PACNTs originates from remarkable interfacial polarization because PA have more contact area with MWCNTs and can reduce leakage current compared with SA.