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 Na, K, Rb, Cs alkoxide and an alkyl lithium compound to form a superbase with the polymer solution; and adding an electrophile to the metalated polymer solution; also provided are the metalated copolymers and the functionalized derivatives therefrom.