The relative permittivity has been measured at audio frequencies and low temperatures for nanocomposites composed of poly(ether imide) (PEI) and BaTiO3 nanoparticles, the nanoparticles in a cavity and polycrystalline BaTiO3. The data at room temperature, for the real part of the relative permittivity versus nanoparticle content of the heat-treated nanocomposites, are found to follow a recently proposed modified Hanai equation. Also, a low-temperature relaxation region (in the vicinity of 20 K) is found in the heat-treated nanocomposites. This relaxation region is also observed in measurements on the nanoparticles packed in a cavity and for the polycrystalline BaTiO3 materials. A relaxation associated with water in the PEI is observed in the as-prepared nanocomposites. Finally, the breakdown strength of the heat-treated nanocomposites is found to decrease as the nanoparticle content increases. Microstructure-level simulations of electric field statistics were carried out and show that matrix field intensification cannot account for all of the variation of breakdown strength with nanoparticle concentration.

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Poly(methyl methacrylate)/MgAl layer double hydroxides (PMMA/MgAl LDH) nanocomposites were prepared by in situ free radical polymerization with the organic modified MgAl-K2 LDH in the methyl methacrylate monomer and initiator of benzoyl peroxide. The morphology of MgAl-K2 LDH and PMMA/MgAl-K2 LDH nanocomposites were investigated by transmission electron microscopy (TEM) and powder X-ray diffraction, indicated that the MgAl-K2 LDH were dispersed in PMMA matrix to form PMMA/MgAl-K2 LDH nanocomposites with heterogeneous morphology comprising both exfoliated and intercalated PMMA/MgAl-K2 LDH nanocomposites . The thermal and mechanical characterization were carried out by thermogravimetric analysis (TGA) ¡Bdifferential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The properties of PMMA/MgAl-K2 LDH nanocomposites exhibit the better thermal and mechanical properties.