Dielectric Properties of Polymer–Particle Nanocomposites Influenced by Electronic Nature of Filler Surfaces

Abstract

The interface between the polymer and the particle has a critical role in altering the properties of a composite dielectric. Polymer-ceramic nanocomposites are promising dielectric materials for many electronic and power devices, combining the high dielectric constant of ceramic particles with the high dielectric breakdown strength of a polymer. Self-assembled monolayers of electron rich or electron poor organophosphate coupling groups were applied to affect the filler-polymer interface and investigate the role of this interface on composite behavior. The interface has potential to influence dielectric properties, in particular the leakage and breakdown resistance. The composite films synthesized from the modified filler particles dispersed into an epoxy polymer matrix were analyzed by dielectric spectroscopy, breakdown strength, and leakage current measurements. The data indicate that significant reduction in leakage currents and dielectric losses and improvement in dielectric breakdown strengths resulted when electropositive phenyl, electron-withdrawing functional groups were located at the polymer-particle interface. At a 30 vol % particle concentration, dielectric composite films yielded a maximum energy density of ~8 J·cm(-3) for TiO2-epoxy nanocomposites and ~9.5 J·cm(-3) for BaTiO3-epoxy nanocomposites.

Enhanced dielectric properties of polyethylene/hexagonal boron nitride nanocomposites

“…An increase in breakdown strength was reported by Siddabattuni et al [13] in 5 vol% epoxy/TiO 2 and epoxy/BaTiO 3 nanocomposites, containing surface modified titania and barium titanate nanoparticles followed by a drastic reduction in breakdown strength at percolation when 15 and 30 vol% of particles were added. The breakdown strength of other BaTiO 3 -based nanocomposites has been shown to be drastically reduced at the percolation threshold [14]; the addition of 20 vol% BaTiO 3 in poly(vinylidene fluorideco-hexafluoropropylene) reduced the breakdown strength from * 380 to * 230 kV/mm.…”

Dielectric performance of high permitivity nanocomposites: impact of polystyrene grafting on BaTiO3 and TiO2

“…18 X-ray scattering demonstrated excellent particle dispersion with no visible clustering; thus, the deleterious effects of percolation that create conduction pathways and increase dielectric loss were avoided. 19 Similarly, Paniagua et al demonstrated that films of PMMA@BaTiO 3 HNPs achieved a maximum extractable energy density of 2 J/cc at intermediate loadings (22% v/v) -a twofold increase over a physically blended nanocomposite at comparable BaTiO 3 loading. 20 These findings were attributed to an increased permittivity and greater energy storage efficiency; however, detailed measurements of dielectric breakdown strength and complex permittivity to elucidate the relative impact of the HNP architecture and PNC morphology were not reported.…”

Dielectric breakdown strength of epoxy bimodal-polymer-brush-grafted core functionalized silica nanocomposites

“…This reveals that the electroactive short brush can overcome the effects of dispersion in some cases. Polar molecules and substituents with greater inductive coefficients, which describe the polarity of the molecule, have been correlated to greater enhancement in DBS [7]. Nevertheless more data from composites with a wide range of short brush molecules is needed to test this hypothesis; two general observations may be drawn.…”

“…In addition, directly bonding the particle to the polymer matrix has been shown to prevent conductive percolation across particle surfaces resulting in reduced interfacial polarization within the composite and increased dielectric breakdown strength [6]. Furthermore, significant reduction in leakage currents and dielectric losses and improvement in dielectric breakdown strengths have resulted when phenyl rings with electronwithdrawing functional groups were grafted to the particle surface [7]. While it is clear that the nanofiller/matrix interface is critical in controlling the dielectric properties, the mechanisms leading to these properties are not fully understood.…”