Successive Synthesis of Asymmetric Star-Branched Polymers Based on Iterative Methodology Using 1,1-Diphenylethylene Derivatives of Alternative Choice at Each Iteration

We have demonstrated an advanced iterative methodology using specially designed 1-[4-(3-bromopropyl)phenyl]-1-phenylethylene (1) or 3,5-bis{3-[4-(1-phenylethenyl)phenyl]propoxy}benzyl bromide (2) of alternative choice at each iteration for the successive synthesis of asymmetric star polymers. The methodology involves only two sets of the following reaction conditions for the entire iterative reaction sequence: (a) a linking reaction of a living anionic polymer with a DPE-chain-functionalized polymer and (b) an in-situ reaction of I or 2 with the anion generated by the linking reaction to reintroduce the DPE functionality. The number of DOE moieties remains unchanged when 1 is used, whereas it doubles when 2 is used. In practice, various arrays of asymmetric star polymers could be successfully synthesized by repeating the iterative reaction sequence, (a) and (b), five times. The structural variation of the stars covers 3-arm AB(2), 5-arm AB(2)C(2), 5-arm AB(2)C(4), 7-arm AB(2)C(2)D(2),9-arm AB(2)C(2)D(4), 11-arm AB(2)C(4)D(4), 15-arm AB(2)C(4)D(8), 9-arm AB(2)C(2)D(2)E(2), 11-arm AB(2)C(2)D(2)E(4), 13-arm AB(2)C(2)D(4)E(4), 15-arm AB(2)C(4)D(4)E(4), 17-arm AB(2)C(2)D(4)E(8), 19-arm AB(2)C(4)D(4)E(8), 23-arm AB(2)C(4)D(8)E(8), and 31-arm AB(2)C(4)D(8)E(16) types. The A, B, C, D, and E segments were polystyrene, poly(alpha-methylstyrene), poly(4-methyl styrene), poly(4-methoxystyrene), and poly(4-trimethylsilylstyrene) segments, respectively. We have corroborated that all of the samples show a high degree of structural and compositional homogeneity by H-1 NMR and SEC-RALLS. The systematic synthesis of multicomponent and multiarmed stars supports the utility and universality of the proposed methodology.