Sulfonated poly(ether ether ketone) (SPEEK) membranes were modified with chemically in situ polymerized polypyrrole (PPy). The effects of temperature and methanol concentration on the solution uptake and the swelling ratio of SPEEK/PPy membranes were investigated. The solution uptake and the swelling ratio of the membranes decreased upon the incorporation of PPy. When the methanol concentration increased, both the solution uptake and the swelling ratio increased to a maximum, and then decreased. FT-IR, XRD, DSC and TGA were used to characterize the modified membranes. The methanol permeability of modified SPEEK membranes decreased upon the incorporation of PPy, and higher selectivity values were found for SPEEK/PPy membranes in comparison with pure SPEEK and Nafion (R) 117 membranes. (c) 2006 Elsevier Ltd. All rights reserved.