In this paper, nanocomposites that contain core-shell Ag/TiO₂ particles as the filler and polytetrafluoroethylene (PTFE) as the matrix were investigated. Two surfactants, namely octyl phosphonic acid (OPA) and pentafluorobenzyl phosphonic acid (PFBPA), were applied to modify Ag/TiO₂ fillers for uniform dispersion in the matrix. Fourier transform infrared spectroscopy analysis of bonds between the TiO₂ shells and the phosphonic modifiers shows Ti⁻O⁻P chemical bonding between the Ag/TiO₂ fillers and the modifiers. Thermogravimetric analysis results show a superior adsorption effect of PFBPA over OPA on the Ag/TiO₂ filler surface at the same weight percentage. For nanocomposites that contain modified Ag/TiO₂ nanoparticles, the loss was reduced despite the high permittivity at the same loading. The permittivity of the nanocomposites by PFBPA is larger than that of OPA, because the more uniform dispersion of inorganic particles in the PTFE matrix enhances the interfacial polarization effect. The mechanism of enhanced dielectric performance was studied and discussed.
Keywords: core–shell structure; dielectric properties; interfacial modification; nanocomposites.