Frequency dependent conductivity of the thin film blend of electroluminescent poly(p-phenylene vinylene) with waterborne polyurethane as ionomer

The frequency dependent conductivity, σ(ω), of the blend containing two different charge carrying material, a conjugated polymer, poly(p-phenylene vinylene), PPV and an ionomer, waterborne polyurethane ionomer, WPUI, was investigated in the frequency (ω) range from 0.1 to 1000 kHz by impedance spectroscopy and compared with the individual materials, PPV and WPUI, respectively. Clear differences could be seen in the dependence of ω on both real and imaginary parts of impedance between WPUI, PPV and the blend film. At high frequencies (>200 kHz), all the three materials, exhibit a power law dependence between σ(ω) and ω as σ(ω)∝ωs. Simulation of s value through theoretical fitting reveals that the s value of the blend (1.108) is in between PPV (1.289) and WPUI (1.035) and signifies the mixed contribution of carrier transport of PPV and WPUI in the blend. The morphology of the blend as observed from atomic force microscopy (AFM) imaging reveals that WPUI connects the islanded parts of PPV and provides a path for carrier conduction. Results observed indicate that carrier transport operates through barrier hopping in these materials and the difference in the dependence of ω on σ in the blend is attributed from the influence of SO3- group in WPUI on the carrier transport of PPV