A proton-exchange composite includes a polymer matrix formed from a
proton-exchange polymer and ionomer particles distributed therein. The
polymer has side chains with ionic groups. The particles have an average
particle size of less than 20 nm and include an oligomeric ionomer that
interacts with the polymer and attracts the ionic groups on its side
chains. The composite may be formed by a method in which an initiator is
bonded to silica particulates. The initiator is used to initiate
polymerization of a precursor monomer to form a salt form of the
oligomeric ionomer bonded to the silica particulates, which is then
reacted with an acid to produce the oligomeric ionomer, thus forming the
ionomer particles. The ionomer particles are dispersed in a solution
containing a solvent and the polymer dissolved therein. The solvent is
removed. The residue is cured to form the composite.