Lowering the percolation threshold of single-walled carbon nanotubes using polystyrene/poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) blends

Single-walled carbon nanotubes (SWCNTs) are introduced into a polymer matrix via a latex-based route resulting in a conductive composite. The percolation threshold for a polystyrene (PS)-based composite prepared with SWCNTs dispersed in water using a conventional surfactant like sodium dodecyl sulfate (SDS) is approximately 0.4 wt%. In this study, SDS is substituted by a conductive polymer latex, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) also known as PEDOT:PSS. This latex can effectively stabilize individual SWCNTs in water and composites prepared with these dispersions show a lower percolation threshold value of 0.2 wt%. The percolation of PEDOT:PSS in PS in a binary polymer blend without SWCNTs is also investigated, and found to occur at a remarkably low loading of 2.2 wt% of the conductive latex. The morphology of the final polymer-filled blend is further investigated and the findings provide an explanation as to why PEDOT:PSS lowers the percolation threshold of the SWCNTs, and in fact has such a low threshold itself without the presence of the nanotubes.