Trifunctional organolithium initiator based on 1,3,5-tris(1-phenylethenyl)benzene. Synthesis of functionalized, three-armed, star-branched polystyrenes

A novel hydrocarbon-soluble, trifunctional organolithium initiator for anionic polymerization has been developed on the basis of the addition of 3 mol of sec-butyllithium with 1,3,5-tris(1-phenylethenyl)benzene. Well-defined, three-armed, star-branched polystyrenes have been synthesized using this initiator in benzene solution with stoichiometric amounts of tetrahydrofuran. The efficiency of the initiation reaction was evaluated by a combination of UV-visible spectroscopy and size-exclusion chromatography analysis. The minimum arm molecular weight for complete initiation was found to be about 5.7 x 10(3) g/mol for this initiator system. The structures of the star-branched polymers were investigated by molecular weight characterization, intrinsic viscosity, and the corresponding values of g' (0.80-0.81); these stars were also compared with an analogous symmetrical, three-armed, polystyrene star prepared by the end-linking reaction of 3 mol of poly(styryl)lithium with 1,3,5-tris(1-phenylethenyl)benzene as the linking reagent. Carbonation of a freeze-dried sample of a living three-armed, omega,omega,omega-tris[poly(styryl)lithium] star prepared with the trifunctional initiator produced the corresponding omega,omega,omega-tricarboxyl-functionalized star with a functionality of 2.9(5).