Polypyrrole/Silicon Carbide Nanocomposites with Tunable Electrical Conductivity

Abstract

Conductive polypyrrole/SiC nanocomposites are fabricated via a facile oxidative polymerization approach using p-toluene sulfonic acid as a dopant and ammonium persulfate as an oxidant. The effects of the nanoparticle loading, ratio of oxidant to monomers, and nanoparticle morphology (spheres and rods) on the hysicochemical properties are investigated. Various characterization methods are carried out to determine the material properties. Thermal gravimetric analysis demonstrates an improved thermal stability of polypyrrole in the polymer nanocomposites (PNCs) with a higher decomposition temperature. The glass-transition temperature and melting temperature of the polymer and its nanocomposites are determined by differential scanning calorimetry with a decreased melting temperature of polypyrrole in the PNCs. The microstructures of pure polypyrrole and PNCs are observed by scanning electron microscopy. Powder X-ray diffraction analysis demonstrates the crytallinity of polypyrrole, and poor crystallinity is observed for the PNCs with higher nanoparticle loading. Fourier transform infrared spectrometry analysis shows a strong interaction between the SiC nanoparticles and the polypyrrole matrix with a shift of C=C stretching vibration of PPy to a lower band. The electron transport in PNCs follows a quasi 3-d variable range hopping conduction mechanism as evidenced by the temperature-dependent conductivity function. Experimental results demonstrate that PPy/SiC PNCs have higher conductivity than that of the pure PPy. The nanorods are also introduced into the polypyrrole matrix. Their effects on the physicochemical properties are investigated and compared. © 2010 American Chemical Society.