Synthesis of well-defined star-branched polymers by coupling reactions of polymer anions consisting of two polymer chains with chain-end-multifunctionalized polystyrenes with benzyl bromide moieties

To synthesize star-branched polymers, we have developed a new methodology of using polymer anions (M-w = ca. 10 kg/mol) consisting of the same or different two polymer chains in the coupling reaction of chain-end-multifunctionalized polystyrenes with 4, 8, and 16 benzyl bromide moieties. The coupling reactions efficiently proceeded to afford 9-, 17-, and 33-arm regular star-branched polystyrenes as well as A(5)B(4), A(9)B(8), and A(17)B(16) asymmetric stars consisting of polystyrene (A) and poly(4-trimethyl-silylstyrene) (B) segments in greater than 85% isolated yields. However, the yields of the coupling reactions were high but not quantitative when either chain-end-functionalized polystyrene with 32 benzyl bromide moieties or a high molecular weight polymer anion (M-w = 20.0 kg/mol) was used.