Aliphatic SPI charge-transfer complex hybrid films for high temperature polymer electrolyte membrane fuel cells

A new method to synthesize polymer electrolyte membranes based on charge-transfer (CT) complexes for high temperature fuel cells is investigated. Aliphatic sulfonated polyimide (SPI) CT complex hybrid films are prepared. Aliphatic units are introduced into the SPI main chain to increase the elasticity compared with aromatic SPI films. Electron-donating compounds are included to form a CT complex, resulting in improved control over mechanical strength, water uptake, and thermal stability. The resulting thermal properties of the SPI CT films are sufficient to operate at elevated temperature (up to 120 °C), and the proton conductivity is comparable to that of Nafion 115. These films are thus promising alternative membranes for high temperature polymer electrolyte fuel cell applications.