Polystyrene-titania composite as a dielectric material

Abstract

Ambient dielectric effects have been studied in rutile-polystyrene compacts as functions of frequency and composition to explore the possibility of their use as electronic materials and characterize them on the basis of existing theories. The systems reveal marked departures from the law of physical mixtures. The dielectric constant ϵ′ and loss ϵ″ increase with increasing titania content at each frequency; both parameters decrease with increasing frequency. The extent of interfacial polarization is substantially augmented as the frequency is reduced. Heterodispersity evidenced from compact densities is a maximum at around 60 wt. % titania where the dissimilar particles fit most loosely into one another forming fairly porous matrices. ϵ′ and (ϵ′)⁻¹ are both curvilinear in the volume fraction, but ϵ′ shows a break at 50 wt. % in the gravimetric-blend plot, reflecting a change in the pattern and degree of interactions. The system conforms to the Clausius-Mossotti equation. The situation is intermediate between the separately possible Böttcher-Bruggeman and Maxwell-Wagner models. This is ascribed to the decrease of dipole moment and ϵ′ with increasing polystyrene owing to the imposition of non-polar environments and consequent lessening of charge density and long- and short-range forces. The variation in sample preparation technique greatly modifies the dielectric properties of these compacts. The composites with a wide range of dielectric properties can be prepared by changing the composition as well as the method of preparation.