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-St₂), were synthesized by hydrosilylation of polybutadiene (∼92 wt % 1,4) with HSiMe₂Cl and HSiMeCl₂, 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.