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-trimethylsilylstyrene) (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.