Well-defined heteroarm star-branched polymers by means of living anionic polymerization

Recent advance in the synthesis of well-defined heteroarm star-branched polymers based on living anionic polymerization is described. Two main methodologies for such star polymer synthesis are currently available. The first method involves the successive linking reactions of multifunctional chlorosilanes with living anionic polymers. The second one is to utilize the reaction of non-polymerizable macromonomers with living anionic polymers, followed by polymerization of another monomer. We have recently synthesized novel well-defined chain-end and in-chain functionalized polystyrenes with a definite number of chloromethylphenyl groups in the range of two and sixteen and successfully applied these functionalized polymers to synthesize star polymers. A variety of well-defined regular and heteroarm star polymers could be synthesized by reacting with living anionic polymers of styrene, alpha -methylstyrene, and isoprene. As a new development of our method, we have used a polymer anion consisting of two same or different polymer chains in the linking reactions with end-functionalized polystyrenes with two chloromethylphenyl groups, thus forming five-arm AA(2)'A(2)" and AB(2)C(2) heteroarm star polymers. These polymer anions were quantitatively prepared by coupling reaction of living anionic polymers with 1,1-diphenylethylene-functionalized macromonomers. Furthermore, a new iterative synthetic approach involving the linking reaction using living anionic polymers and the subsequent introduction of 1,1-diphenylethylene moieties has been developed for the synthesis of A(2)A(2)'A(2)" and A(2)B(2)C(2) heteroarm star polymers.