We successfully synthesized a novel self-crosslinkable, pendent sulfonated poly(arylene ether ketone) for proton exchange membranes with high proton conductivity, excellent dimensional stability, and extraordinary methanol resistance. The chemical structure of the self-crosslinkable polymer SQNPAEK-AC-x was analyzed by H-1 NMR. Without using any catalysts or a separate cross-linker, crosslinked SC-SQNPAEK-x membranes can be obtained by thermal treatment. The crosslinked network greatly suppresses the swelling ratio as well as water uptake of the membrane, meanwhile keeping the proton conductivity of the membrane at a high level. The highest proton conductivity is achieved by SC-SQNPAEK-2.5 membrane with a conductivity of 0.220 S cm(-1) at 80 degrees C after crosslinking, which is much higher than commercial Nation 117 membrane under the same conditions. The low water uptake depresses methanol crossover, which results in low methanol permeability. Mechanical property and oxidation stability also increased. Overall, the superior performance of these self-crosslinked membranes demonstrates the potential application of these materials as polyelectrolytes for proton exchange membrane fuel cells (PEMFCs). (C) 2016 Elsevier B.V. All rights reserved.