Synthesis and characterization of model 4-miktoarm star co- and quaterpolymers

The synthesis of well-defined, nearly monodisperse, 4-miktoarm (from the Greek word μικτο meaning mixed) star co- and quaterpolymers of the A 2 B 2 and ABCD types, is described. A is polystyrene, B polybutadiene, C polyisoprene, and D poly(4-methylstyrene). The synthetic approach involves the reaction of tetrachlorosilane with the active chain end centers of the first arm under conditions unfavorable to chain coupling or linking, followed by a stoichiometric addition (titration) of the living polymer of the second or the third arm, and finally by an excess of the living polymer of the last arm. The sequence of addition of the different living polymers and the monitoring of the progress of the linking reaction by SEC are the key for successful synthesis