Highly cross-linked membranes were prepared using a pore-filling technique for application in polymer electrolyte fuel cells (PEFCs). The electrolyte that fills the porous substrate should have a higher ion exchange capacity (IEC) than membranes prepared by a casting method. Hence, a cross-linking agent is employed to prevent the polymer electrolyte from dissolving in water. The goal of this study is to improve the chemical, mechanical, and electrochemical stability in membranes without decreasing the IEC. We evaluated the membrane characteristics using two different types of cross-linking agents-1,3,5-triacryloylhexahydro-1,3,5-triazine (C1) with three cross-linkable sites and N,N'-ethylene bisacrylamide (C2) with two cross-linkable sites. The membranes with Cl improved the chemical and electrochemical properties without a remarkable decrease in the IEC and proton conductivity compared to the membranes created with C2. Moreover, the Cl membrane also demonstrated an improvement in the electrochemical durability during the accelerated lifetime test. (C) 2014 Elsevier B.V. All rights reserved