Sulfonated multi-block copolymers (SMBPs) were successfully synthesized from precursors of hydrophilic and hydrophobic block oligomers. The hydrophilic block oligomer was synthesized using 1,2-bis(4-fluorobenzoyl)-3,4,5,6-tetraphenylbenzene (BFBTPB) and 4,4'-(2,2-diphenylethenylidene) diphenol (DHTPE). The hydrophobic block oligomer was prepared by bis(4-hydroxyphenyl) sulfone and bis(4-fluorophenyl) sulfone. The sulfonation was taken selectively on hydrophilic block segment as well as para position of the pendant phenyl groups with concentrated sulfuric acid. To control the IEC the stoichiometry mole ratios were changed with hydrophilic blocks of 10, 13 and 17 mol%. The structural properties of SMBPs were studied by FT-IR, H-1 NMR spectroscopy, thermogravimetric analysis (TGA), and atomic force microscope (AFM). The water uptakes were 9.7-42.3% at 30 degrees C and 14.3%-70.4% at 80 degrees C with changing the ion exchange capacities. The resulted ion exchange capacities (IEC) were 1.09-1.63 meq./g. The highest power density of a fuel cell using SMBP 17 (IEC = 1.63 meq./g) and Nafion 211 was 0.41 and 0.45 W/cm(2), respectively, at 0.6 V. Copyright (c) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.