Synthesis of Model Multigraft Copolymers of Butadiene with Randomly Placed Single and Double Polystyrene Branches

Model multigraft copolymers of butadiene (Bd) and styrene (St) with randomly placed trifunctional, poly(Bd- g -St), and tetrafunctional branch points, poly(Bd- g -St 2 ), were synthesized by hydrosilylation of polybutadiene (∼92 wt % 1,4) with HSiMe 2 Cl and HSiMeCl 2, respectively, followed by reaction of the resultant silicon−chloride groups along the backbone with polystyryllithium (PSLi). The extent of hydrosilylation was controlled by appropriate adjustment of the [silane]/[C C] ratio. Characterization carried out by size exclusion chromatography (UV and RI detector), low-angle laser light scattering, differential refractrometry, and NMR spectroscopy indicated that the synthesized branched molecules have a high degree of molecular and compositional homogeneity.