Electrochromic behavior and electrical percolation threshold of carbon nanotube/poly(pyridinium triflate) composites

The electrochromic composite material based on poly(4,4′-(1,4-phenylene)bis(2,6-diphenylpyridinium) triflate) (PV) and multiwall carbon nanotubes (MWCNTs) was prepared by non-covalent interaction where PV acts as a functionalizing agent for MWCNTs. The increase in electrical conductivity and improvement of electrochromic properties of PV is attributed to the formation of MWCNTs networks. The percolation threshold for PV/MWCNTs occurred at 0.3 wt% of MWCNTs. Corresponding value of critical exponent was found to be 2.8 which is far from universal values. At practically the same electrochromic contrast the coloring and bleaching time for composites with higher polymer concentration (8 mg/mL) decreased from 600 ms to 300 ms and from 500 ms to 350 ms, respectively. It was demonstrated that further increase of MWCNTs weight content did not lead to the improvement of electrochromic properties.