Although sulfonated aromatic polymers are thought to be one of the promising materials for proton exchange membranes, most of them suffer from significant drop of proton conductivity with decrease in humidity, which causes poor cell performance under partially hydrated condition. In this study, to improve proton conduction at low hydration level, two different multiblock copolymer membranes based on different hydrophobic oligomers are prepared and their hydrophilic/hydrophobic phase-separated morphology is examined. Both multiblock copolymer membranes show better developed phase separation than the random copolymer membrane. Multiblock copolymer having more hydrophobic oligomer exhibits better interconnection between hydrophilic channels than that having less hydrophobic oligomer. This can lead to an improvement of both proton conductivity and cell performance under partially hydrated condition. Copyright (C) 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.