Development of self-poled PVDF/MWNT flexible nanocomposites with a boosted electroactive β-phase

In the present study, we report a simple fabrication method for poly(vinylidene fluoride) PVDF/MWCNT flexible nanocomposite films with a boosted electroactive phase that enhanced the dielectric and piezoelectric properties. The PVDF films were prepared by using the phase inversion method for which water was a non-solvent. Initially, neat PVDF films were prepared in a temperature-controlled non-solvent with varying temperatures from 5 °C to 40 °C respectively. Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), and differential scanning calorimetry (DSC) were carried out to confirm the electroactive phase and percentage crystallinity of the film. The electroactive β-phase of PVDF exhibited an enhancement with a decrease in temperature. At 5 °C, PVDF showed a β-fraction of ca. ∼54.4%, with a percentage crystallinity of ca. ∼57.4%. With the systematic addition of Multi-walled carbon nanotubes (MWCNTs), it was observed that the β-fraction and the crystallinity of PVDF were enhanced. A dramatic improvement in the electroactive phase was observed upon the addition of 0.25 wt% MWCNTs, with a β-phase content of PVDF of ca. ∼93.8% and crystallinity of ca. ∼61.8%. The augmented polar phase changed the dielectric and piezoelectric properties of the PVDF nanocomposites.