Semicrystalline proton-conductive membranes with sulfonated amorphous phases

Proton-conductive membranes, exhibiting high chemical and thermomechanical resistance, have been obtained by s-PS films with the β crystalline phase and a sulfonated amorphous phase. These membranes can be obtained by a solid-state procedure on δ form films, which allows an easy and uniform sulfonation of the phenyl rings of the amorphous phase and preserves the crystalline phase, followed by suitable thermal treatments leading to the δ → β crystal-to-crystal transition. The high degree of sulfonation of the amorphous phase makes this phase highly hydrophilic and proton conductive while the presence of the high melting and thermodynamically stable β phase assures high chemical and thermomechanical stability.