A series of imidazolium-functionalized poly(ether ether ketone)s (PEEK-ImOHs) were successfully synthesized by a two-step chloromethylation-Menshutkin reaction followed by hydroxide exchange. PEEK-ImOH membranes with ion exchange capacity (IEC) ranging from 1.56 to 2.24 mmol g(-1) were prepared by solution casting. PEEK-ImOHs show selective solubility in aqueous solutions of acetone and tetrahydrofuran, but are insoluble in lower alcohols. PEEK-ImOH membranes with IEC of 2.03 mmol g(-1) have high hydroxide conductivity (52 mS cm(-1) at 20 degrees C), acceptable water swelling ratio (51% at 60 degrees C), and great tensile strength (78 MPa), and surprising flexibility (elongation-to-break of 168%), and high thermal stability (Decomposition temperature: 193 degrees C). In addition, PEEK-ImOH membranes show low methanol permeability (1.3-6.9 x 10(-7) cm(2) s(-1)). PEEK-ImOH membrane was tested in methanol/O-2 fuel cell as both the HEM and the ionomer impregnated into the catalyst layer; the open circuit voltage is 0.84 V and the peak power density is 31 mW cm(-2). (C) 2013 Elsevier B.V. All rights reserved.