Nanocomposites and nanomaterials

Influence of frequency and temperature on electrical resistivity of polymer-based nanocomposites  
Zhydenko I.1,2, Karbovnyk I.1,3, Klym H.1, Chalyy D.2 
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

Low-temperature behavior of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) thin layers reinforced with carbon nanotubes however, is much less analyzed. Different reliability issues and effects of nanofiller properties on the temperature dependence of con-ductivity in this range remain a rather open question. 
In this work we report the results of the investigation of the influence of frequency and, most importantly, temperature on electrical resistivity of PEDOT:PSS micrometer thick films reinforced with multi-walled carbon nanotubes (MWCNT), prioritizing the temperature range from 10 to 300 K.
Cooling and heating modes of electrical measurements were realized by exploiting functions of Cryocon 32 temperature controller from Cryogenic Control Systems Inc., ac electrical measurements at different frequencies were done with the automated E7-20 RLC-meter from LLC “ZAPADPRIBOR” which allows registering active and reactive resistances in the range from 10–5 to 109 Ω. Standard 1 V sinewave was used as an ac excitation signal.
It is shown that two types of layers of conductive polymer PEDOT:PSS and polymer PEDOT:PSS with the addition of multilayer carbon nanotubes were prepared, with a thickness in the range of 30–50 μm. The electrical resistance of such layers was investigated depending on the temperature in the range of 10–300 K. The observed temperature behavior of PEDOT:PSS resistance is consistent line with one-dimensional variable hopping model, which speaks speaking in favor of possible partial contribution of tunneling conduction, as well as thermal activation mechanism and, possibly, Coulomb electron-electron interaction. The effect of adding nanotubes to the polymer matrix results also leads to the hysteresis of resistance measured in heating–cooling cycles, which is probably likely to be stimulated by the difference in thermal expansion coefficients of the matrix and the filler and by slow processes determined by these coefficients.