Preparation and properties of proton conducting organic–inorganic hybrid membranes based on hyperbranched aliphatic polyester and phosphoric acid

A series of organic–inorganic hybrid membranes based on phosphoric acid and hyperbranched aliphatic polyester (Boltorn™ H20) used as electrolytes for polymer electrolyte membrane fuel cells (PEMFC) operated at the temperature higher than 100 °C have been prepared via a sol–gel process, and characterized using 31P MAS NMR. Boltorn™ H20 was doped into the hybrid membranes at different levels to provide high hydrophilic and water conservation property. A high proton conductivity was obtained with suitable H20 doping level, and the membrane with the highest proton conductivity remained a conductivity of 5 × 10−4 S cm−1 even after holding for 7 h at 130 °C under 30% relative humidity. The TGA/DTG results have shown that the obtained hybrid membranes were stable up to 200 °C.