Nanomaterials and nanocomposites

Impedance analysis of PEDOT:PSS/CNT Composites Below Percolation Threshold  
I. Karbovnyk1, H. Klym2, D. Chalyy3, D. Lukashevych 3, I. Zhydenko3
1 Ivan Franko National University of Lviv, Dragomanova Str., 50, Lviv, 79005, Ukraine,
E-mail: ivan_karbovnyck@yahoo.com
2 Lviv National Polytechnic University, Lviv, Ukraine
3 Lviv State University of Life Safety, Lviv, Ukraine

Polymer nanocomposites such as those based on PEDOT:PSS matrix filled with carbon nanomaterials are typically known to have low percolation threshold. That means that even small loadings of conductive nanotubes having high aspect ratio already lead to the formation of at least one (although usually more) conductive pathway. While shape, size and geometry of filler basically determine whether electrical percolation occurs another important factor is the dispersion of nanofiller inside the matrix, which is not easily achievable and often prevent observing low percolation threshold.
In this presentation we analyze electrical response of PEDOT:PSS polymer layers with incorporated single-walled and multi-walled nanotubes in amounts that hypothetically should be sufficient for percolation to occur. Morphological analysis by scanning electron microscopy, however, indicates the formation of isolated bundles inside the polymer matrix and low probability of connection between adjacent bundles.
To study how such nanocomposite behaves under AC electrical excitation we used impedance spectroscopy as a tool.  Impedance spectra in the range of frequencies from 100 Hz to 1 MHz were measured with Keysight Е4990А analyzer capable of measuring absolute value of the sample impedance in the range from 10-1 to 109 Ohms with less than 1% error.
Based on collected impedance data for nanocomposite samples with different concentration of incorporated nanotubes (both single-walled and multi-walled ones) equivalent circuit models describing conductivity processes in these materials are proposed and discussed.