Unzipped multiwalled carbon nanotubes-incorporated poly(vinylidene fluoride) nanocomposites with enhanced interface and piezoelectric β phase

► MWCNTs were oxidatively unzipped to endow the surface with oxygen-containing groups. ► These treated MWCNTs enabled the magnified interface and thus the interfacial interaction. ► Enhanced interface and electrostatic interaction induce more piezoelectric β phase of PVDF.