Miguel Iban Delgado Rosero

Polyvinylidene fluoride (PVDF) and hypophosphorous acid (H₃PO₂) are combined to synthesize solid polymer electrolyte membranes using the solution cast method. Electrochemical impedance spectroscopy measurements are used to find the conductivity, and those values are plotted as a function of relative humidity (% RH) to which the membranes are kept. In agreement with the modified Onsager, the results show growth in conductivity as % RH increases, which states that ionic mobility of a polar polymeric phase increases as levels of absorbed water by the polymeric membrane increase. The high values of conductivity observed at high concentrations of H₃PO₂ (σ = 9.83 × 10⁻³ S cm⁻¹ for x = 60% wt) are attributed to the increase of charge carriers and the dissociation of ions in an aqueous phase. The synthesized membranes are tested as electrolytes in a fuel cell and the voltage and power density plotted as a function of the current density with maxim values of the power density of 2.88 mW cm⁻² for a 30% wt membrane.

The addition of nanoparticles as fillers has a significant influence in modifying the dynamic conditions and avoiding crystallization in polymer composites. In this work, (PEO)₄CF₃COOLi electrolyte and multi-walled carbon nanotubes (MWCNTs) were used to prepare composites by a solution method. The formation of the new composite was evidenced by the experimental results obtained from DSC analysis and infrared spectroscopy (FTIR). The impedance spectroscopy analysis shows a notable decrease in the resistance, which is attributed to an interaction between the oxygen of the polymer and the Li⁺ cations of the salt, and the interactions between the electrolyte and the MWNTs. Values of dc conductivity of 8.42 × 10⁻⁴ S cm⁻¹ at room temperature are obtained at a concentration of 2.0 wt.% MWCNT in the whole electrolyte. The results indicate that membranes can be used in technological devices such as batteries and gas or moisture sensors.

Polymeric membranes of poly(ethylene oxide) (PEO) and sodium trifluoroacetate (PEO:CF₃COONa) combined with different concentrations of aluminum oxide (Al₂O₃) particles were analyzed by impedance spectroscopy, differential scanning calorimetry (DSC) and thermogravimetry (TGA). DSC results show changes in the crystalline fraction of PEO when the concentration of Al₂O₃ is increased. TGA analysis showed thermal stability up to 430 K showing small changes with the addition of alumina particles. The decrease in crystalline fraction for membranes with low Al₂O₃ concentration is associated with the increase in conductivity of (PEO)₁₀CF₃COONa + x wt.% Al₂O₃ composites.

Se prepararon membranas de Polivinil Difluoruro y Acido Hipofosforoso (PVDF/H3PO2) con diferentes concentraciones de ácido. Los resultados de calorimetría diferencial de barrido (DSC), presentan un escalón característico de la transición vítrea alrededor de 250 K. También se observan dos anomalías endotérmicas: una cercana a 357 K debido a la evaporación de agua, y otra cerca a los 422 K atribuida a la fusión de la fase cristalina del PVDF. Los análisis de Espectrometría de masas (MS) acoplado con Termogravimetría (TGA), revelan la posible presencia de moléculas de (C2H2O) y ácido fluorhídrico (HF), esto plantea la posibilidad de que el H3PO2 perdió un átomo de hidrógeno y se enlazó a la cadena polimérica del PVDF desplazando un átomo de flúor. Se evidencia la presencia de moléculas de agua a diferentes temperaturas, que sugiere la formación de agua superficial, interna y estructural en el sistema polímero-acido. Esta característica, hace que el sistema PVDF/H3PO2 sea propuesto como electrolito solido en celdas de combustible.