A series of novel sulfonated poly(arylene ether ketone) (SPAEK) copolymers with pendant sulfoalkyl groups are prepared via nucleophilic polycondensation reactions. The sulfonate content of the SPAEK copolymers can be controlled easily by adjusting the ratio of the sulfonated and unsulfonated monomer feeds. The structures of the synthesized sulfonated copolymers are confirmed by H-1 NMR and Fourier transform infrared spectra. The microstructures of the membranes are investigated by transmission electron microscopy. Mechanical properties, thermal and oxidative stabilities, water uptake, swelling ratio, proton conductivity, and methanol permeability of the membranes are systematically investigated. The results demonstrated that the membranes have good performance. The proton conductivities of the side-chain-type SPAEK-100 membrane reach 0.051 and 0.152 S cm(-1) at 25 and 120 degrees C, respectively. The methanol permeabilities of the side-chain-type SPAEK membranes are in the range of 0.12 Chi 10(-7)-335 Chi 10(-7) m(2) s(-1), which is lower than that of the Nafion 117 membrane, i.e., 23.8 Chi 10(-7) m(2) s(-1). A higher relative selectivity than that of Nafion 117 is also observed. These results indicate that there is a great potential for side-chain-type SPAEK membranes to be used in proton exchange membrane fuel cell applications. (C) 2014 Elsevier B.V. All rights reserved.