New proton-conductive fuel cell membranes have been produced by the linkage of acidic functional groups to aryloxy side units attached to a polyphosphazene macromolecular chain. The functional groups include sulfonic acid, phosphonic acid, and sulfonimide units. The different functional groups impart different water retention, proton conduction, and methanol resistance to the membranes. Special advantages are foreseen for uses in direct methanol fuel cells. (c) 2006 Wiley Periodicals, Inc.