Ultralow Electrical Percolation Threshold in Poly(styrene-co-acrylonitrile)/Carbon Nanotube Nanocomposites

Abstract

Here, we demonstrate a new method that involves in situ copolymerization of styrene and acrylonitrile monomers in the presence of multiwall carbon nanotubes (MWCNTs) and commercial poly(styrene-co-acrylonitrile) (SAN) beads, for the preparation of electrically conducting SAN/MWCNT nanocomposites with a significantly low percolation threshold of the CNTs. At a constant CNT loading, the conductivity of the nanocomposites was increased with increasing content (weight percent) of the SAN beads, indicating the formation of a more continuous network structure of the CNTs in SAN matrix. Thus, the electrical conductivity (1.38 × 10–6 S·cm–1) of the nanocomposites with 40 wt % SAN beads increased to 8.07 × 10–5 S·cm–1 when the SAN bead content was increased to 70 wt % at constant CNT loading (i.e., 0.1 wt %). The morphology study revealed the dispersion and distribution of the MWCNTs selectively in the in situ polymerized SAN phase of the nanocomposites, leading to an increase in effective concentration of the CNTs in the in situ polymerized SAN phase of the nanocomposites. Thus, the percolation threshold of the nanocomposites was reduced to a lower value (0.032 wt % MWCNT), which was not reported elsewhere for SAN/MWCNT nanocomposites with unmodified, commercial MWCNTs of similar qualities. This report discusses detailed methodology of the process as well as other characteristics of the SAN/MWCNT nanocomposites.