AC conductivity: Figure 4.19(a) shows the frequency dependent electrical conductivity of PCL5 electrolyte. The result shows that AC conductivity changes with temperature. The AC conductivity of the PEO/CoCl2 electrolyte increases with temperature is given in Table 4.4, which is the common characteristic of disordered materials. An increase in ac conductivity with frequency and temperature indicates charge transported by hopping through the defect sites along the polymer chain [70]. Also the increase in electrical conductivity with increasing temperature is due to the buildup of ordered polycondensed rings, which allow charge transport. This temperature dependence of conductivity at higher temperatures suggests that the hopping mechanism of
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Figure 4.22(a) shows the sharp endothermic peak observed and the melting temperature of PEO at 67 oC has been decreased to 54.4 oC for 5 wt%. The decrease in melting point (Tm) might be related to a decrease in the relative percentage of crystallinity (χc) of the film. The endothermic curves also indicate a reduction in PEO crystallinity. The study of the degree of crystallinity is very significant one to understand the change in the thermal characteristics induced due to CoCl2. The relative percentage of crystallinity χc has been calculated using Equation (2.20) and the values of Tg, Tm, ΔHm and χc are summarized in Table …show more content…
These results are well agreed with the XRD results [74]. Decrease in the percentage of χc designates that Co2+ effectively distorted the main chain dynamics of PEO. The value of Tg was decreased from –68 to –80 oC with the increase of CoCl2 concentration are shown in Figure 4.22(b). Above glass transition temperature, the polymeric chain becomes more flexible resulting in enhanced segmental mobility of the PEO polymer chain. Lower Tg usually leads to easier chain relaxation and is associated with fast ion conduction mechanism
Figure 4.22(a) shows the sharp endothermic peak observed and the melting temperature of PEO at 67 oC has been decreased to 54.4 oC for 5 wt%. The decrease in melting point (Tm) might be related to a decrease in the relative percentage of crystallinity (χc) of the film. The endothermic curves also indicate a reduction in PEO crystallinity. The study of the degree of crystallinity is very significant one to understand the change in the thermal characteristics induced due to CoCl2. The relative percentage of crystallinity χc has been calculated using Equation (2.20) and the values of Tg, Tm, ΔHm and χc are summarized in Table …show more content…
These results are well agreed with the XRD results [74]. Decrease in the percentage of χc designates that Co2+ effectively distorted the main chain dynamics of PEO. The value of Tg was decreased from –68 to –80 oC with the increase of CoCl2 concentration are shown in Figure 4.22(b). Above glass transition temperature, the polymeric chain becomes more flexible resulting in enhanced segmental mobility of the PEO polymer chain. Lower Tg usually leads to easier chain relaxation and is associated with fast ion conduction mechanism