The base copolymers can be sulfonated, or in accordance with a further aspect of this invention, may be phosphorylated, carboxylated, quaternary-aminoalkylated or chloromethylated, and further modified to yield --CH2 PO3 H2, --CH2 NR3 + where R is an alkyl, or --CH2 NAr3 + where Ar is an aromatic (arene), to provide a cation or anion exchange membrane.