Enhanced electrical conductivity of polyurethane-polyaniline composites containing core–shell particles through conductive-shell effect

Abstract

In this study SiO2 nanoparticles coated with polyaniline (PANI) shell of various thicknesses have been fabricated successfully by in situ polymerization of aniline on the silica surface through the chemical bonding between amino groups of silica surface and aniline. The addition procedure of dodecylbenzenesulfonic acid plays a key role on whether the thick-shell nanoparticles can be prepared successfully or not. The SiO2-PANI core–shell nanoparticles and PANI oligomers were reacted with isocyanates to prepare the conductive polyurethane-PANI-silica hybrid films. Under the same PANI content in nanocomposites, the hybrid films containing the nanoparticles with the thicker PANI shell show superior enhancement on electrical conductivities compared to those containing the thinner-PANI-shell nanoparticles. On the 5-wt.% PANI content, the surface resistance of the nanocomposites can reduce to ∼106Ω/sq, lowering two orders, while the nanoparticles with 1.35-wt.% PANI shell are replaced by those with 13.8-wt.% PANI shell in use. According to the general effective media analysis, the percolation threshold (0.0277) is much lower than the critical volume fraction (0.16) for random packing in three dimensions. As a result of the low percolation threshold, we infer that the conducting core–shell nanoparticles form electrical channels due to the surface connection effect, resulting in the momentous enhancements in the electrical conductivity.