there is provided a method of introducing functionality into a copolymer of an isoolefin and an alkylstyrene at the alkylbenzyl carbon atom comprising the steps of : forming a solution of said copolymer in a hydrocarbon solvent ; adding to said polymer solution an alkali metal cs , k , na alkoxide and an alkyl lithium compound to form a superbase with the polymer solution ; and adding an electrophile to said base polymer solution also provided are the metalated copolymers and the functionalized derivative therefrom .