Electrical investigation of polythiophene–poly(vinyl acetate) composite films via VTF and impedance spectroscopy

Polythiophene (PTP) and poly (vinyl acetate) (PVAc) composite films were prepared by chemical oxidative polymerization method with FeCl₃ as an oxidant, in methanol at room temperature. Their dc conductivities as a function of temperature (313–358 K) were measured. An attempt has been made to investigate the effect of temperature and concentration of ferric chloride oxidant on the conductivity of polythiophene–poly(vinyl acetate) composite films. For fixed wt% of PVAc, the dc electrical conductivity of the film initially increases with the molar concentration of FeCl₃ and then decreases with the further increase in the concentration of FeCl₃. The temperature dependence of conductivity showed Arrhenius behavior. The conductivity isotherms show VTF behavior which is typical for ion conducting polymers. The Nyquist plot of Z′ vs. Z″ were plotted for frequency range 100 Hz–200 kHz and temperature range of 313–358 K. These plots consist of semicircles for higher temperatures. This suggests Debye type relaxation mechanism. The equivalent circuit consists of parallel combination of bulk resistance R_B and bulk capacitance C_B. The bulk resistance R_B of the samples decreased with increase in temperature.