Nanocomposites and nanomaterials

PEDOT:PSS polymer matrices reinforced with carbon nanotubes: electrical and structural properties
Zhydenko I.1,2, Chalyy D.2, Karbovnyk I.1,3, Klym H.1
1Lviv Polytechnic National University, 12, Bandera Str., Lviv-79013, Ukraine
E-mail: klymha@yahoo.com, halyna.i.klym@lpnu.ua
2Lviv State University of Life Safety, 35, Kleparivska Str., Lviv-79000, Ukraine 
3Department of Electronics and Computer Technologies, Ivan Franko National University of Lviv, 107, Tarnavskogo Str., Lviv-79000, Ukraine

In this of work we experimentally analyze structural features and electrical behavior of PEDOT:PSS polymer layers with inclusions of high-purity single-walled (SWCNTs) or multi-walled carbon nanotubes (MWСNTs) – two types of nanotubes that are characterized by high structural perfection.
All investigated samples show lowest impedance (highest conductivity) at room temperature and electrical conductivity decrease upon cooling. General trend is that Re(Z) slightly increases with frequency from 1 kHz to up to some threshold frequency and then drops rapidly. This threshold frequency for pure PEDOT:PSS and PEDOT:PSS/SWCNTs samples is about 100 kHz and is somewhat lower for composite layers with MWCNTs.
Most notable temperature effect on the real part of the impedance of fabricated polymer/CNTs composite layers is that Re (Z) increases drastically starting from certain temperature, which is different for samples with different composition. For pure polymer this occurs already at 80…90 K and below 60 K Re (Z) is almost out of the measurable range. For layers reinforced with SWCNTs, increase of impedance is more gradual and even more so for MWCNTs-reinforced composites. In the latter case, reliable measurements can be performed even at temperatures as low as 40K. 
In samples with incorporated CNTs the conditions for residual water storage are potentially different due to structural changes introduced by specific nanofiller, so that time needed for complete water removal is different and the process is eventually finished at different temperature. This assumption is further supported by the fact that samples with MWCNTs show slower growth of real impedance with decreasing temperature and generally have higher conductivity at lowest measured temperatures.