Synthesis of a Model 3-Miktoarm Star Terpolymer

The synthesis of a well-defined, near monodisperse, star terpolymer with three different arms, i.e., polyisoprene, polystyrene, and polybutadiene, is described. The synthetic approach involves the reaction of polyisoprenyllithium with an excess of methyltrichlorosilane followed, after removed of the excess of methyltrichlorosilane, by a stoichiometric addition (titration) of polystyrillithium and finally by a small excess of polybutadienyllithium. The sequence of the addition of the different living polymers is very critical. After linking, the excess of the polybutadienyllithium was terminated with methanol and removed by fractionation. Characterization was carried out by size-exclusion chromatography, low-angle laser light scattering, laser differential refractometry, osmometry, and NMR and UV spectroscopy.