Proton conducting blends of poly(4-vinylimidazole) with phosphoric acid

The synthesis, thermal, and conduction properties of blends prepared from poly(4-vinyl-imidazole), P-4VI, and phosphoric acid are reported. The number of moles of phosphoric acid per polymer repeat unit, x, was varied from 0≤x≤2. These blends can be cast into homogeneous films. Thermogravimetric analysis (TGA) illustrates that these blends are chemically stable up to about 150°C. Differential scanning calorimetry (DSC) shows that the softening temperature of the blends decrease from 77°C for x=1 to −8°C for x=2. The DC conductivity increases with x and reaches ∼10−4 S/cm for x=2 at ambient temperature.