BaTiO3/hyperbranched polyester/methacrylate core-shell nanoparticles were studied by varying the shell thickness and the methacrylate ratio. We demonstrated that coalescence typically observed in traditional composites employing polymer matrices is significantly reduced. By modifying the shell thickness, the equivalent filler fraction was tuned from 7 wt. % to 41 wt. %. Obtained permittivities were compared with reported models for two-phase mixtures. The nonlinear behavior of the dielectric constant as a function of the equivalent filler fraction has been fitted with the Bruggeman equation. Methacrylate groups reduce by a decade the loss factor by improving nanoparticles adhesion. The permittivity reaching 85 at 1 kHz makes core-shell nanoparticles a promising material for embedded capacitors.

International audienceExtensive research is being conducted on the development of inorganic/organic nanocomposites for a wide variety of applications in microelectronics, biotechnologies, photonics, adhesives, or optical coatings. High filler contents are usually required to fully optimize the nanocomposites properties. However, numerous studies demonstrated that traditional composite viscosity increases with increasing the filler concentration reducing therefore significantly the material processability. In this work, we synthesized inorganic/organic core-shell nanocomposites with different shell thicknesses. By reducing the shell thickness while maintaining a constant core size, the nanopar- ticle molecular mass decreases but the nanocomposite filler fraction is correlatively increased. We performed viscosity measurements, which clearly highlighted that intrinsic viscosity of hybrid nanoparticles decreases as the molecular mass decreases, and thus, as the filler fraction increases, as opposed to Einstein predictions about the viscosity of traditional inorganic/polymer two-phase mixtures. This exceptional behavior, modeled by Mark-Houwink-Sakurada equation, proves to be a significant breakthrough for the development of industrializable nanocomposites with high filler contents