Assemblies of Titanium Dioxide-Polystyrene Hybrid Nanoparticles for Dielectric Applications

Macroscopic assemblies of hybrid nanoparticles composed of titanium dioxide core surrounded by covalently grafted polystyrene corona have been prepared by a combination of phosphonate coupling and “click” chemistry. The attached polymer chains existed in the brush regime, with grafting density inversely proportional to the degree of polymerization. Solution casting afforded preparation of robust films of the composite material where all the polymer chains were covalently bound to the uniformly distributed inorganic particles. Inorganic content from 60 to 80 wt % (27 to 50 vol %) was obtained by varying the molecular weight of polystyrene as well as by using the mixture of high and low molecular weight polymer for grafting. The TiO2 grafted with 105 g/mol polystyrene had a volume fraction of nanoparticles of 27% and exhibited glass transition at 110 °C and ∼100% extensibility above T g. Thin films of this material had a dielectric constant of 6.4 and a dielectric loss of 0.04 at 1 kHz.