Crystalline and amorphous phase identification from the tanδ relaxation peaks and impedance plots in polymer blend electrolytes based on [CS:AgNt]x:PEO(x-1) (10 ≤ x ≤ 50)

摘要

In this study, we report the identification of crystalline and amorphous phases in [CS:AgNt]x:PEO(x-1)(10?≤?x?≤?50) chitosan based blend electrolytes through the study of loss tangent (tanδ) relaxation peaks and impedance plots. From the impedance plots, the crystalline and amorphous phases were distinguished. The first semicircle due to amorphous phase was found to be absent for the sample incorporated with 50?wt % PEO. Enormous spherulites due to crystalline phases were found for the same PEO concentration sample as inspected by optical surface morphology microscope. The XRD results strongly support the impedance plots and morphological appearances. The dielectric constant and DC conductivity were determined to be increasing with increasing PEO concentration up to 20?wt % and then decreasing with further increase of PEO concentration. The high values of dielectric constant (ε′) were observed at higher temperatures, attributing to the change of phase transition of PEO. Electric modulus function was studied to understand the mechanism of ion transport through the conductivity or viscoelastic relaxation. The complete semicircular arc with a diameter coinciding withMraxis was obtained at 70?°C, indicating the occurrence of ion transport by conductivity relaxation. The α- and β-relaxations, relating to crystalline dipole rotation and dipole orientation in amorphous regions, respectively, are accurately identified from the studies of tanδ relaxation peaks versus frequency at different temperatures. From 60?°C and above, β-relaxation peaks were found to be the only peaks in tanδ plots. Moreover, the second semicircle in the impedance plots were also tends to be vanished with the rise of temperature to 60?°C and above. These findings have indicated a complete dissolution of crystalline phases. The melting point was obtained from the differential scanning calorimetry (DSC) measurement.