The recent progress of our research on proton exchange membranes for fuel cell applications is reviewed. In particular, we have focused on the effect of the molecular structures of fluorine-free sulfonated aromatic polymers on membrane properties (e.g., proton conductivity, chemical and mechanical stability). We identified an optimized hydrophilic molecular design (sulfophenylene as SPP), that is, SPP simultaneously exhibited the highest proton conductivity and excellent mechanical stability over a wide range of humidities.
- Junpei Miyake
- Kenji Miyatake
