EFFECT OF GLYCEROL ON THE ELECTRICAL PROPERTIES AND PHASE BEHAVIOR OF CASSAVA STARCH BIOPOLYMERS

films of different concentrations of glycerol/starch (g/s) blends were prepared and analyzed by impedance spectroscopy (is), differential scanning calorimeter (dsc) and thermogravimetric analysis (tga). the dc-conductivity of the films increases by increasing both the glycerol content and temperature. a power-law dispersive behavior of the frequency-dependent conductivity at high frequencies has been observed in all g/s films in the blend compositions prepared, similar to that observed in other solid ionic conductors and known as a "universal dynamic response." the electrical conductivity enhancement is consistent with the subtle changes in the -oh glycerol groups coordination with the starch chains introduced by increasing the glycerol content and temperature. a stable single phase is revealed under the electrical measurement conditions up to approximately 100 °c for all concentrations, but the stability can be maintained up to higher temperatures (～150 °c) at glycerol concentrations below g/s = 0.4.