Silyl-functional pseudo-telechelic polyisobutylene terpolymers

A method for preparing a silyl-functional, pseudo-telechelic polyisobutylene terpolymer, said method comprising reacting, in the presence of a Lewis acid and a solvent,

• (A) an isobutylene monomer;
• (B) an isopropenylphenyl comonomer having the formula
• (C) a vinylphenyl comonomer of the formula
• wherein R′ is a divalent non-aromatic hydrocarbon group having 2 to 6 carbon atoms, R″ is independently selected from alkyl groups having 1 to 10 carbon atoms or aryl groups having 6 to 10 carbon atoms, R is a divalent non-aromatic hydrocarbon group having 2 to 6 carbon atoms, X is independently a hydrolyzable group and n is independently 1, 2 or 3, and wherein the benzene ring of components (B) and (C) may optionally be substituted with at least one hydrocarbon group having 1 to 12 carbon atoms, with the proviso that rAC is greater than 1 and rAB is less than 1, wherein rAB is the reactivity ratio of said isobutylene in the presence of said comonomer (B) and said solvent and rAC is the reactivity ratio of said isobutylene in the presence of said comonomer (C) and said solvent.