Sulfonated poly(arylene ether sulfone) (SPES) has received considerable attention in membrane preparation for proton exchange membrane fuel cell (PEMFC). But such membranes are brittle and difficult to handle in operation. We investigated new membranes using SPES grafted with various degrees of octylamine. Five new materials made from sulfonated polyethersulfone sulfonamide (SPESOS) were synthetized with different grades of grafting. They were made from SPES. with initially an ionic exchange capacity (IEC) of 2.4 meq g(-1) (1.3 H(+) per monomer unit). Pristine SPES with that IEC is water swelling and becomes soluble at 80 degrees C, its proton conductivity is in the range of 0.1 S cm(-1) at room temperature in aqueous H(2)SO(4) 1 M, similar to that of Nafion (R). After grafting with various amounts of octylamine, the material is water insoluble; membranes are less brittle and show sufficient ionic conductivity. Proton transport numbers were measured close to 1. (C) 2011 Elsevier B.V. All rights reserved.