Thermal, electrical and structural study of polymeric membranes based on poly(vinyl alcohol), chitosan and phosphoric acid

In this work, polymeric membranes films based on poly(vinyl alcohol) (PVA) and chitosan (CS) were prepared at a molar ratio of 80:20 (PVA/CS), which were mixed with phosphoric acid (H3PO4) at different concentrations. Thermal analysis shows that the glass transition temperature, the melting point of the crystalline part and the degradation of the membrane for the systems PVA/CS 80:20 + 10% H3PO4 are around 56 degrees C, 190 degrees C and 217 degrees C. These anomalies moved toward lower temperatures with respect to pure PVA. Regarding the electrical response, the DC conductivity is thermally activated, following an Arrhenius-type behavior. The activation energy is 0.12 eV with a maximum ionic conductivity of 9.45 x 10(-3) (omega center dot cm)(-1) at 200 celcius for 40% H3PO4 concentration. The X-ray analysis at room temperature shows a peak around 2 theta = 20 degrees, whose intensity and width depend on the amorphous character of the sample. Hence, the polymer electrolyte consisting of PVA:CS (80:20) + 40% H3PO4 looks very desirable and promising for the fabrication of polymer electrolyte membranes for fuel cells.