Polymer nanocomposite membranes based on sulfonated poly(ether ether ketone) and trisilanol phenyl POSS for fuel cell applications

摘要

Polymer nanocomposite membranes based on sulfonated poly(ether ether ketone) (SPEEK) (degree of sulfonation 60%) containing varying amounts of open cage trisilanol phenyl polyhedral oligomeric silsesquioxane (POSS) ranging from 0.5 to 5 phr (parts per hundred parts of the polymer resin) were prepared and characterized. The composite membranes were characterized by water uptake, proton conductivity, methanol permeability, X-ray diffraction (XRD), scanning electron microscopy (SEM), and ther-mogravimetric analysis (TGA). The presence of nanofillers in the composite films was confirmed by XRD and SEM-EDX. The domain size of POSS (for 0.5 phr sample) as determined by SEM was in the range of 50-100 nm. Thermal stability of SPEEK remained unaffected by the addition of varying amounts of POSS. Equilibrium water uptake of all the composite membranes (maximum 42%) was higher than that of pure SPEEK membrane (23%) at 80°C. Proton conductivity of SPEEK as measured by two probe method increased upon incorporation of POSS and maximum value was obtained when the POSS content was 2 phr (w/w), that is, 4.5 mS/cm, which was higher when compared with SPEEK (1.5 mS/cm) and Nafion (3.4 mS/cm) at 90°C. Methanol permeability of composite membranes was lower than that of SPEEK/Nafion membrane.