Abstract
Molecular dynamics (MD) simulation was performed to investigate the structure and dielectric permittivity of poly(vinylidene fluoride)- (PVDF-) based composites with different contents of barium titanate (BT). The β-phase PVDF model with 100 structural units and the spherical BT particle model with a radius of 0.495 nm were built and applied in the initial models with three PVDF macromolecular chains and BT particles for the MD simulations of the BT/PVDF composites. The influences of BT content on the morphological structure, the free volume fraction, and glass transition temperature of the composites were explored according to the simulated results and the experimental ones of X-ray diffraction (XRD) and scanning electron microscope (SEM). A model was proposed to predict the static dielectric permittivity of the composites, the results of which were compared with the Cole-Cole fitting results of dielectric spectroscopy. Attempts were made to reveal the structure evolution and the micropolarization mechanism with the increasing content of BT.
Highlights
Polymer-based dielectric composites have been widely applied in the industries of information, energy, electrical, and electronics thanks to their good processability, excellent mechanical properties, low dielectric loss, and high breakdown strength [1, 2]
In view of the fact that BaTiO3/Poly(vinylidene fluoride) (PVDF) dielectric composites (BT/PVDF) have been extensively researched while the Molecular dynamics (MD) simulations on the structure and polarization mechanism of the composites are very limited, this paper focuses on the simulation of the structure of barium titanate (BT)/PVDF composites and the prediction of dielectric permittivity by MD simulations
We reported the MD simulations on the structure, glass transition temperature, and dielectric permittivity of BT/PVDF composites
Summary
Polymer-based dielectric composites have been widely applied in the industries of information, energy, electrical, and electronics thanks to their good processability, excellent mechanical properties, low dielectric loss, and high breakdown strength [1, 2]. Poly(vinylidene fluoride) (PVDF), a ferroelectric polymer with relatively high dielectric permittivity [9, 10], was widely investigated in the formation of the dielectric composites with addition of ferroelectric ceramic fillers, such as BaTiO3, SrTiO3, and Ba0.6Sr0.4TiO3 [11,12,13,14,15,16,17,18]. A dielectric permittivity of 27.9 at 1 kHz and breakdown strength of 117 kV/mm were reported by Ma et al [19] for PVDF-based composites with 30 vol% core-shell structured fillers of vinyl functionalized BaTiO3 wrapped with thiolterminated PVDF. Feng et al [30] used MD simulations to study the dielectric behaviors of polymer composites with threedimensional particle networks and revealed the increased dielectric permittivity of the composites when the particle network formed and the adjacent particles were polarized due to the continuous coupling effect. In comparison with the experimental data, the polarization mechanism of the composites was proposed
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