Influence of Single-wall Carbon Nanotubes and Polypyrrole Thin Layer Coating on the Electrical Conductivity of PolyHIPE Foams

Abstract

Conducting poly(styrene-co-divinylbenzene)/single wall carbon nanotube (SWCNT) polyHIPE (polymerized high internal phase emulsion) composite foams were successfully synthesized via emulsion template polymerization. The effect of various SWCNT loadings, 0–1.4 wt.%, on the electrical conductivity and surface morphology of resulting composite foams was investigated. The incorporation of small amount of SWCNT as conducting nanofiller resulted in formation of a percolative network on the surface of polyHIPE foam. As expected, increasing the weight fraction of SWCNT above the percolation threshold, 0.2 wt.%, increased the conductivity of the nanocomposite foams up to 0.8 wt.%, while further increase had no significant change in the electrical conductivity. Scanning electron micrographs indicated that the incorporation of SWCNT led to the microstructural changes in the typical structure of resulting polyHIPE foam. This morphological change can be attributed to the use of an anionic surfactant as SWCNT dispersing agent in the aqueous phase and to subsequent partial instability of the HIPE. The prepared nanocomposite foams were then covered with an ultrathin layer of polypyrrole (PPy) via chemical oxidative polymerization of pyrrole in the presence of dodecylbenzenesulfonic acid sodium salt (DBSNa) as dopant. The shift of bands in the Fourier transform infrared (FTIR) spectrum of the PPy/SWCNT hybrid foam in comparison with the neat PPy coated foam suggested a specific interaction between the PPy chains and SWCNT that would change the conducting polymer conformation and packed structure. The delocalized π-electrons in SWCNT/PPy bond through noncovalent or π-π interactions resulted in the hybrid polyHIPE nanocomposite foams with enhanced electrical conductivity.