Correlation of electrical, thermal, and crystal parameters of complex composite films based on polyethylene oxide (PEO) doped by copper sulfate (CuSO4)

Ionic conductivity and the conductivity mapping of PEO/CuSO4 complex composite films are investigated to show the effect of the complexation of the Cu+2 and SO4−2 ions on the PEO matrix. Adding CuSO4 into the PEO matrix decreases the crystallinity degree of PEO films and consequently enhances the ionic conductivity and charge diffusion due to increasing the segmental motion of PEO. The FTIR spectra demonstrate the complexation of the Cu+2 ions to the ether oxygen in PEO films, while the SO4−2 ions behave as free ions in the polymer matrix as elucidated in the vibrational modes of PEO/CuSO4 thin films. Introducing CuSO4 into the PEO matrix improves the thermal stability of the complex composite films. Moreover, the conductivity of the pure PEO film is 1.67 × 10−4 S/cm at room temperature. Increasing CuSO4 concentration in the PEO films to 20% increases the ionic conductivity up to 6.13 × 10−4 S/cm.