High-Performance Semicrystalline Poly(ether ketone)-Based Proton Exchange Membrane

A novel semicrystalline poly­(ether ketone) (PEK)-based proton exchange membrane (semi-SPEK-x) has been developed. Through a one-step sulfonation and hydrolysis, a poly­(ether ketimine) precursor transforms into PEK and ion-conducting groups are introduced. With an ion-exchange capacity ranging from 1.49 to 2.00 mequiv g–1, the semi-SPEK-x polymers exhibit a semicrystalline feature in both dry and hydrated states. Owing to the semicrystalline domains inside the polymer, the obtained membrane exhibits low water uptake and low volume swelling ratio. More importantly, the semicrystalline structure lowers methanol permeability and, consequently, improves the overall performances of direct methanol fuel cells.