Understanding the effect of CNTs on the piezoelectric properties of PVDF and PVDF–TrFE: combined experimental and simulation study

Fluoropolymers like poly(vinylidene fluoride) (PVDF) and their copolymers have gained wide recognition in the diverse field of energy due to their better piezoelectric and ferroelectric properties. Electrospun nanofibers of poly(vinylidene fluoride-<i>co</i>-trifluoroethylene) or PVDF-TrFE were prepared using an electrospinning process. Carbon nanotubes (MWCNTs) were added to the polymer matrix and their effect was studied through morphological, structural, and thermal analysis. PVDF-TrFE with the addition of CNT nanofillers provided enhancement in the piezoelectric coefficient value by about 20%. Building upon these promising experimental findings, atomistic molecular dynamics (MD) simulations were done to have a microscopic understanding of the measured piezoelectric response of β phase crystalline PVDF and gain valuable insights into the observed piezoelectric enhancements. The piezoelectric response was quantified by calculating the piezoelectric <i>d</i>₃₃ coefficient. Investigations were done by applying a constant electric field and sinusoidal alternating electric field of order 0.01 V nm^-1 to 0.2 V nm^-1. A negative piezoelectric effect was observed and the β-phase PVDF crystal showed an increase in magnitude of <i>d</i>₃₃ by about 12% upon addition of CNTs and this was attributed to increased specific polarizability near the CNT surface.