Data on a temperature-dependent thermic and electrical properties of a novel blend polymeric system based on poly(vinyl alcohol), chitosan and phosphoric acid

In this work, data on a temperature-dependent thermic and electrical properties in a novel blend polymer electrolyte membranes based on poly(vinyl alcohol) (PVA) and chitosan (CS) doped with H3PO4 at different concentrations were prepared by solution casting method. Their phase behavior and ionic conductivity were studied by DSC, TGA and IS. These membranes exhibit good proton conductivity of the order of 10−2 Scm−1 at 200 °C and the understanding of the H3PO4 at different concentrations effect in the polymer electrolyte membranes is crucial for possible applications in fuel cells. The data have not been reported nor discussed in the research paper to be submitting.


a b s t r a c t
In this work, data on a temperature-dependent thermic and electrical properties in a novel blend polymer electrolyte membranes based on poly(vinyl alcohol) (PVA) and chitosan (CS) doped with H 3 PO 4 at different concentrations were prepared by solution casting method. Their phase behavior and ionic conductivity were studied by DSC, TGA and IS. These membranes exhibit good proton conductivity of the order of 10 À2 Scm À1 at 200 C and the understanding of the H 3 PO 4 at different concentrations effect in the polymer electrolyte membranes is crucial for possible applications in fuel cells. The data have not been reported nor discussed in the research paper to be submitting. © 2020 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4.0/).

Data
The DC conductivity, s 0 , can be determined from the resistance of the volume of the sample obtained from the impedance graphs, Nyquist plots (-ImZ vs ReZ), by extrapolating the circular part of the spectrum to the real axis Z 0 , using s 0 ¼ d/AR, where R is the intercept with the Z 0 axis, d is the thickness of the membrane and A the contact area of the sample with the electrodes. It is also possible to determine s 0 from the adjustment of the experimental data to the Jonscher model [4], where s 0 is the DC conductivity (independent of the frequency), A is a pre-exponential factor related to the frequency of regime change, u p , as A ¼ s 0 /(u p ) n and n is a value between 0 and 1, where the values of n close to zero indicate that the correlation between the ions is greater than for the values close to 1, which would be the case where the ionic jumps are random (Debye model). From the impedance data, Z 0 (u) and Z 00 (u), the values of the real conductivity, s 0 were obtained using the relation, The experimental data (TGA, DSC and IS) are reported in Tables 1e6.
The Table 1 shows the weight percent loss in three different temperature regions for all the membranes.
Specifications Value of the Data Weight percent loss a different temperature regions give information about the thermal stability which is important to know the work temperature. Temperature dependent data of heat flow give the characteristic values (glass transition, melting point, decomposition temperature and their enthalpy changes) of the membranes Temperature dependent data of resistance and conductivity provide a detailed insight to the membranes and their possible application to fuel cells. Table 2 shows the characteristic values of the membranes using DSC. Tables 3 and 4 show the resistance values of the membranes extrapolated from the Nyquist diagrams in relation to the temperature and concentration of phosphoric acid. Table 5 shows the membrane parameters and activation energies for two temperature regions using the Arrhenius model. Table 6 shows the parameters obtained from Jonscher model adjustment to the membranes with (PVA:CS) þ 10% H 3 PO 4 . Table 2 Characteristic values of the membranes using the DSC.  Table 3 Resistance values of the membranes extrapolated from the Nyquist diagrams.

Experimental design, materials, and methods
Hydrolyzed poly(vinyl alcohol) (PVA, Mw: 31,000e50,000 g/mol), Chitosan (CS) and phosphoric acid (H 3 PO 4 , Mw: 98g/mol) were obtained from Sigma Aldrich, and used as received without any further purification. A solution of acetic acid at 2% by volume of distilled and deionized water was prepared. Then, a solution of PVA and CS was established at the weight ratio of 80:20. Thus, PVA:CS (80:20) and phosphoric acid at concentrations from 10% to 40% was defined in the mixture of acetic acid and distilled and deionized water.
TGA (Q500, TA Instruments) was used to investigate sample weight changes as a function of time and temperature under a N 2 atmosphere at a flow rate of 50 ml/min. DSC (Q100, TA Instruments) was used to measure the enthalpies, and temperatures of the various thermal events that might occur in the membranes when they are thermally treated. The electrical characterization of the membranes was done by impedance spectroscopy (IS) using a Wayner Kerr impedance analyzer at an excitation signal of 100 mV and 20 Hze5 MHz frequency range. The dc conductivity, s, was calculated from the Nyquist plots (-ImZ vs ReZ). The bulk resistance, R bulk , was obtained from the intercept of the circular arc of the spectra with the real axis, and using the formula s ¼ d/AR, where d is the thickness and A the contact area of the sample. Fig. 1 shows the Nyquist diagrams for (PVA:CS) þ 30% H 3 PO 4 to isotherms between 30 C and 200 C, where a semicircle is observed at high frequencies, and which is associated with the electrical response in the volume of the sample. At low frequency regime there is a linear tendency associated with the effects of the interface with the electrodes. The resistance and conductivity values of all membranes is show in Tables 3 and 4 Fig . 2a shows the logarithm of the real part of the AC conductivities obtained from ec (2) as a function of the logarithm of the frequency (20 Hze5 MHz) at several isotherms for (PVA:CS) þ 10% H 3 PO 4 . In solid line the fit for typical curves obtained from ec (1) (Fig. 2b) and the parameters are show in Table 6. The DC conductivity (s 0 ) values are in agreement with those calculated from Nyquist plots (see Table 4). On the other hand, the n-exponent parameter, except for 160 C, takes values between 0 and 1; values greater than 1 could be associated with high values of energy storage in the collective movements of the short-range ions and which cannot be explained by Jonscher model.