Enhanced Quasilinear Dielectric Behavior of Polyvinylidene Fluoride via Confined Crystallization and Aligned Dipole Polarization

It is a daunting task to completely eliminate the intrinsic nonlinear ferroelectric behavior of polyvinylidene fluoride (PVDF) and simultaneously inherit its high dielectric constant. In the current study, the scalable fabrication of PVDF-based all-organic polymer dielectric films was achieved by melt blending and hot-stretching processes. The inclusion of the 60 vol % polymethyl methacrylate (PMMA) component could totally degrade the crystallization ability of PVDF due to the dipole/dipole interactions or hydrogen bonding between the −CF2 groups of PVDF and the carbonyl groups of PMMA, thus significantly decreasing hysteresis loss. The intense extensional flow field was demonstrated to be efficient for inducing highly aligned amorphous dipoles in the PMMA/PVDF composite films, greatly enhancing the dielectric constant and breakdown strength. As a result, a quasilinear dielectric behavior with pretty low remanent polarization of the as-prepared PMMA/PVDF composite films was observed, exhibiting an impressive discharge energy density as high as 17.6 J/cm3 at the electric field of 650 MV/m with a high discharge energy efficiency of 88.0%. Such a high energy density and low hysteresis loss are highly attractive in PVDF or its copolymer-based all-organic dielectric polymer films. The new insight in the relationship between the microscopic amorphous structure and macroscopic dielectric performance is conducive to alleviating the intrinsic nonlinear ferroelectric behavior of PVDF, facilitating its application in the field of film capacitors.