A series of 0−3 metal oxide−polyolefin nanocomposites are synthesized via in situ olefin polymerization, using the following single-site metallocene catalysts: C 2-symmetric dichloro[rac-ethylenebisindenyl]zirconium(IV), Me2Si( t BuN)(η5-C5Me4)TiCl2, and (η5-C5Me5)TiCl3 immobilized on methylaluminoxane (MAO)-treated BaTiO3, ZrO2, 3-mol %-yttria-stabilized zirconia, 8-mol %-yttria-stabilized zirconia, sphere-shaped TiO2 nanoparticles, and rod-shaped TiO2 nanoparticles. The resulting composite materials are structurally characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), 13C nuclear magnetic resonance (NMR) spectroscopy, and differential scanning calorimetry (DSC). TEM analysis shows that the nanoparticles are well-dispersed in the polymer matrix, with each individual nanoparticle surrounded by polymer. Electrical measurements reveal that most of these nanocomposites have leakage current densities of ∼10−6−10−8 A/cm2; relative permittivities increase as the nanoparticle volume fraction increases, with measured values as high as 6.1. At the same volume fraction, rod-shaped TiO2 nanoparticle−isotactic polypropylene nanocomposites exhibit significantly greater permittivities than the corresponding sphere-shaped TiO2 nanoparticle−isotactic polypropylene nanocomposites. Effective medium theories fail to give a quantitative description of the capacitance behavior, but do aid substantially in interpreting the trends qualitatively. The energy storage densities of these nanocomposites are estimated to be as high as 9.4 J/cm3.

Aluminum oxide encapsulated high-permittivity (ε) BaTiO 3 and ZrO 2 core-shell nanoparticles having variable Al 2 O 3 shell thicknesses were prepared via a layer-by-layer methylaluminoxane coating process. Subsequent chemisorptive activation of the single-site metallocene catalyst [rac-ethylenebisindenyl]zirconium dichloride (EBIZrCl 2 ) on these Al 2 O 3 -encapsulated nanoparticles, followed by propylene addition, affords 0-3 metal oxide-isotactic polypropylene nanocomposites. Nanocomposite microstructure is analyzed by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, differential scanning calorimetry, atomic force microscopy, and Raman spectroscopy. The in situ polymerization process yields homogeneously dispersed nanoparticles in a polyolefin matrix. Electrical measurements indicate that as the concentration of the filler nanoparticles increases, the effective permittivity of the nanocomposites increases, affording ε values as high as 6.2. The effective permittivites of such composites can be predicted by the Maxwell-Garnett formalism using the effective medium theory for volume fractions (ν f ) of nanoparticles below 0.06. The nanocomposites have leakage current densities of ∼10 -7 -10 -9 A/cm 2 at an electric field of 10 5 V/cm, and very low dielectric loss in the frequency range 100 Hz-1 MHz. Increasing the Al 2 O 3 shell thickness dramatically suppresses the leakage current and high field dielectric loss in these nanocomposites.

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