Block type polymer electrolyte membranes (PEMs) were prepared by casting an aqueous solution of a block copolymer, poly(vinyl alcohol-b-styrene sulfonic acid) (PVA-b-PSSA), and by cross-linking the PVA chains with glutaraldehyde (GA) solution at various GA concentrations to investigate the effect of the cross-linking conditions on the properties of the block-type PEMs. The proton conductivity and the permeability of methanol through the block-type PEMs decreased with increasing GA concentration. The permeability coefficient through the block-type PEM prepared under the conditions of c(GA) = 0.05% is about 6 times lower than that through Nafion115 (R) under the same measurement conditions. A test cell for a direct methanol fuel cell constructed using the block-type PEMs delivered 32.4mWcm(-2) of P-max at 116mA cm(-2) of load current density at 1M methanol solution, which is almost the same value obtained with Nafion115 (R). However, at high methanol concentrations (>9 M), the P-max of the block-type PEM was 17.8mWcm(-2), and was 86% higher than that of Nafion (R) 115. (C) 2014 Elsevier Ltd. All rights reserved.