The sulfonation selectivity of various pendant phenyl groups in poly(arylene ether ketone) (Ph-3F-PAEK) is invested via the postsulfonation approach. The sulfonated Ph-3F-PAEKs with different degrees of sulfonation (DS) are quantitatively synthesized by controlling the length of the segments that cannot be sulfonated. In this study, H-1 NMR and FT-IR are used to confirmed the structures of the polymers and the experimentally DS values were calculated by H-1 NMR. The experimentally observed DSs are corresponding to the theoretical values expected from the monomer ratios. All the sulfonated membranes have excellent mechanical properties (with a Young's modulus > 13 GPa, a tensile strength > 55 MPa and the elongation > 10%). Thermogravimetric analysis (TGA) is used to characterized the thermal stability of these polymers, and all the polymers show excellent thermal properties at high temperatures. The methanol permeability values of Ph-3F-SPAEKs in the range of 0.37 x 10(-7) cm(2) s(-1) to 4.12 x 10(-7) cm(2) s(-1) are much lower than that of Nafion (R) 117 (1.55 x 10(-6) cm(2) s(-1)). It should be noted that the polymer with highest DS, Ph-3F-SPAEK-100 with an ion exchange capacity of 2.16 mequiv.g(-1), exhibits high proton conductivity of 0.187 S cm(-1) at 80 degrees C, which is also higher than that of Nafion (R) 117. (c) 2009 Elsevier B.V. All rights reserved.