Controllable Synthesis of Highly Conductive Polyaniline Coated Silica Nanoparticles Using Self-Stabilized Dispersion Polymerization

Highly conductive silica/polyaniline (PANi) core/shell nanoparticles (NPs) were synthesized in various diameters (from 18 to 130 nm) using self-stabilized dispersion polymerization. The polymerization was carried out in an aqueous/organic liquid system at -30 °C. In this system, the organic phase plays a key role in directing para-direction oriented polymerization of the PANi on the surface of silica NPs. Because of its para-direction polymerized structure, the synthesized silica/PANi core/shell NPs exhibited enhanced electrical conductivity (25.6 S cm(-1)) compared with NPs (1.4 S cm(-1)) prepared by homogeneous polymerization. The conductivities and BET surface areas were 25.6 S cm(-1)/170 m(2) g(-1) (18 nm in diameter), 22.5 S cm(-1)/111 m(2) g(-1) (35 nm in diameter), 18.3 S cm(-1)/78 m(2) g(-1) (63 nm in diameter), and 16.4 S cm(-1)/53 m(2) g(-1) (130 nm in diameter). In this series, increased para-coupling along the polymer backbone was elucidated using several characterization techniques, including Fourier transform infrared (FTIR), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) spectroscopy. As-prepared silica/PANi core/shell NPs exhibited capacitance as high as 305 F g(-1).