SYNTHESIS AND CHARACTERIZATION OF MODEL 4-MIKTOARM STAR COPOLYMERS AND QUATERPOLYMERS

The synthesis of well-defined, nearly monodisperse, 4-miktoarm (from t he Greek word mulkappatauos meaning mixed) star co- and quaterpolymers of the A2B2 and ABCD types, is described. A is polystyrene, B polybut adiene, C polyisoprene, and D poly(4-methylstyrene). The synthetic app roach involves the reaction of tetrachlorosilane with the active chain end centers of the first arm under conditions unfavorable to chain co upling or linking, followed by a stoichiometric addition (titration) o f 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 additio n of the different living polymers and the monitoring of the progress of the linking reaction by size-exclusion chromatography (SEC) are the key for successful synthesis. Characterization was carried out by SEC , low-angle laser light scattering, laser differential refractometry, membrane and vapor pressure osmometry, and NMR spectroscopy.