Investigation of physical aging of carbon nanotube/PEDOT:PSS nanocomposites by electrochemical impedance spectroscopy

In this work, thin films based on multi-walled carbon nanotubes (MWCNT)- poly(3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT:PSS) were prepared by solution mixing method. The dispersions were deposited on a flexible thin polyimide Kapton-HN 500 substrate by drop casting technique. The physical aging effect on the thin films as a function of MWCNT concentration ranging from 0.025 wt. % to 0.1 wt. % were investigated at room temperature by electrochemical impedance spectroscopy (EIS) over a wide range of frequency from 40 Hz to 110 MHz. It was found that the MWCNT concentration has a considerable influence not only on the conductivity but also on the aging rate of the nanocomposite films. It was also observed that the influence of aging on the electrical properties of the nanocomposites decreases with increasing amount of MWCNT concentration, due to the electron restriction mobility in the polymer chains at the vicinity of PEDOT:PSS/MWCNT interfaces. While the relative resistance change in the pure PEDOT:PSS polymer is 21.2 %, this change is found to be 6.8 % at 0.1 wt. % of MWCNT. Moreover, the aging effect on the MWCNT/PEDOT:PSS nanocomposites was considered within an equivalent complex R-C circuit model based on the obtained impedance data. This model was used to extract the electrical fitting parameters of the nanocomposites at different MWCNT concentrations.