Multilayered polyelectrolyte complexes (PECs) modified proton exchange membranes are successfully prepared from alternating deposition of oppositely charged polyelectrolyte chitosan (CS) and sulfonated poly (aryl ether ketone) bearing carboxyl groups (SPAEK-C) on the surface of Nafion (R) 117 via the layer-by-layer (LBL) method. The cross-linked PEC-coated Nafion (R) membranes (c-PEC-coated Nafion (R) membranes) are prepared from heat-induced cross-linking between CS and SPAEK-C via formation of amide bonds. Fourier transform infrared spectroscopy (FT-IR) verifies that cross-linking between ammonium groups of CS and carboxyl groups of SPAEK-C occurs by the formation of amide bonds. The morphology of the membranes is studied in detail by SEM. The c-PEC-coated Nafion (R) membranes exhibit low water uptake (23.5%, 80 degrees C), water swelling (14.0%, 80 degrees C) and methanol permeability (2.7 x 10(-7) cm(2) s(-1)). Proton conductivity of the c-PEC-coated Nafion (R) membranes increase at elevated temperature, reaching the value of 0.131 S cm(-1) at 80 degrees C. These results show that cross-linking of layered CS/SPAEK-C films can effectively reduce water uptake, water swelling and methanol permeability while improve the dimensional stability and maintain high proton conductivity. (C) 2009 Elsevier B.V. All rights reserved.