Two step modification of poly(vinyl alcohol) by UV radiation with 2-hydroxy ethyl methacrylate and sol-gel process for the application of polymer electrolyte membrane

Two step modification of poly(vinyl alcohol) (PVA) by UV radiation and sol-gel process was used to prepare the modified PVA membranes. From the first step modification of PVA by UV radiation with 2-hydroxy ethyl methacrylate (HEMA) monomer, the poly(2-hydroxy ethyl methacrylate) (PHEMA) modified poly(vinyl alcohol), PVAHEMA, was obtained and characterized by Fourier transfer infrared spectra (FTIR) and optical polarizing microscopy for the chemical compositions and morphology. With the second step modification of sol-gel process, the organic-inorganic hybrid sol-gel material, PVAHEMA-SiO₂, was prepared. Both of the modified PVA, (PVAHEMA and PVAHEMA-SiO₂), were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA). To prepare the alkaline solid polymer electrolyte, the various PVAHEMA and PVAHEMA-SiO₂ membranes were immersed in 40 wt% KOH solution to form the KOH containing polymer electrolyte membranes. And then their performances were conducted with ac impedance spectroscopy to evaluate the ionic conductivity through the membranes. At room temperature, the ionic conductivity increased from 0.044 to 0.073 S/cm for the PVAHEMA membrane; whereas the ionic conductivity was about 0.11 S/cm for the PVAHEMA-SiO₂ membranes. Compared to other reports in references, our hybrid sol-gel membrane is a highly ionic conducting alkaline solid polymer electrolytes membrane.