The present invention relates to a proton exchange membrane having a polymer comprising of a main chain and a branch chain connected to said main chain wherein the chemical formula for said branch chain is and where n is an integer. Said main chain is a polymer selected from the group that includes: aliphatic polymers, aliphatic block polymers, and aliphatic random copolymers. The fabrication method for said polymers comprises the steps of: reacting a polymer having a benzene ring in its branch chain with a sulfo-alkylated chemical reagent and a catalyst in an anhydrous solvent in an inert atmosphere; separating the resulting sulfo-alkylated polymer; and acidifying to obtain said fabricated polymer. Proton exchange membranes made with these polymers are pliant, do not expand much during wet conditions, and, are chemically, hydrolytically, dimensionally and thermally stable.