A series of poly(arylene ether ketone)s containing azidomethylbenzoyl side chains were fabricated through a three-step process involving polymerization of methylated copolymers, followed by bromination and azido-functionalized with sodium azide. Click reaction was applied to introduce locally and densely populated sulfophenyl group into the aromatic copolymer backbone. Ion exchange capacity (IEC) was indirectly controlled by the contents of brominated methylene moieties as precursors for azido-functionalization. Structures of the copolymers were confirmed by FT-IR and H-1 NMR. Transmission electron microscopy (TEM) showed good phase separated morphology with ionic cluster sizes in the range of 2-20 nm. Meanwhile, the sulfonated copolymers exhibited high proton conductivity in the range between 0.082 and 0.113 S cm(-1) at 80 degrees C and 100% relative humidity (RH). The methanol permeability of these membranes was in the range between 4.07 x 10(-7) and 10.00 x 10(-7) cm(2) s(-1). Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.