Abstract
Using impedance spectroscopy (IS), differential scanning calorimetry (DSC),thermogravimetric analysis (TGA), and infrared spectroscopy (IR) tech-niques to study the polymer electrolyte membranes based on poly(vinylalcohol) (PVA) and hypophosphorous acid (H3PO2) with different tita-nium oxide nanoparticles (TiO2) concentrations. The polymer systems(1−x)(H3PO2/ PVA) +xTiO2were prepared using the sol-casting methodand different weight percent of TiO2,x≤10.0. The DSC results showthat the glass transition for molar fraction P/OH = 0.3 appears around 75°Cand for the samples doped with TiO2around 35°C; the melting pointfor all membranes appear around 175°C. The FTIR spectra show changesin the profiles of the absorption bands with the addition of H3PO2andthe different concentrations of TiO2. The IS results show dielectric andconductivity relaxations as well as a change in DC ionic conductivity withthe TiO2content. The order of the ionic conductivity is about10−2S/cmfor 5.0of TiO2. The TGA in the heating run shows water loss that is inagreement with DC conductivity measurements.
Highlights
Resumen Usando las técnicas de espectroscopia de impedancia (IS), calorimetría de barrido diferencial (DSC), análisis termogravimetrico (TGA) y espectroscopia infrarroja (FTIR) se estudió el sistema polimérico (1 − x)(H3PO2/ poly(vinyl alcohol) (PVA)) + xTiO2 el cual fue preparado usando el método de sol-casting a diferentes porcentaje de peso de nanopartículas de TiO2, x ≤ 10.0
The results show that dc conductivity values decrease with increasing temperature in the range where the membranes release water as noted in the results of TGA indicating that the proton transport membranes is provided in regions containing water that form a liquid phase or aqueous solution with H3PO2
Composite polymer electrolyte based on PVA-H3PO2,with constant molar ratio P/OH = 0.3, and reinforced with nanoparticles TiO2, homogenously dispersed, have been prepared
Summary
The precursors materials were hypophosphorous acid (H3PO2), PVA, and titanium oxide (TiO2) with particle size smaller than 50 nm (Sigma Aldrich Chemicals). Constant amounts of TiO2 nanoparticles were added to the solution, maintaining the mixture under agitation until it became homogeneous. After additional two hours under agitation the mixture, at room temperature, was poured into glass vessels under dry atmosphere (desiccator with sulphuric acid) by several days to obtain membranes. The thermal characterization was carried out by using a TA Instrument DSC Q100 calorimeter at a thermal scan of 10°C/min under a nitrogen atmosphere in a temperature range between −75°C and 250°C. The dc conductivity was determined from the bulk sample resistance using the impedance plots, Z, by extrapolation of the circular portion of the spectrum to the real axis Z , and using the expression σ0 = d/AR being R the intercept with the Z -axis, d the membrane thickness, and A the sample contact area with the electrodes. Spectra were obtained at room temperature and under a nitrogen atmosphere
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