The invention includes compositions comprising at least first and second
polymers and optionally a third polymer wherein acid subunits, basic
subunits and elastomeric subunits are contained in the polymers. In one
aspect, the composition comprises a ternary polymer blend comprising an
acidic polymer comprising acidic subunits, a basic polymer comprising
basic subunits and an elastomeric polymer comprising elastomeric
subunits. In an alternate aspect, the composition comprises a binary
polymer blend which comprises acidic or basic subunits in one polymer and
a copolymer comprising the other of the acidic or basic subunit and an
elastomeric subunit. Such polymer compositions may be formed into a
membrane having electrochemical properties which permit the use of such a
membrane in an electrochemical device.