Abstract
The synthesis of well-defined four- and six-arm star branched polymers in which arms differ either in molecular weight or composition has been achieved via a new iterative approach based on living anionic polymerization using 1,1-diphenylethylene (DPE) derivatives. Each stage in the iteration involves two reactions: a living functionalization reaction of living anionic polymer with DPE derivatives and an in-situ reaction of the resulting linked product having two anions with 1-4-(4-bromobutyl)phenyl]-1-phenylethylene to introduce two DPE moieties into the polymer. In each living functionalization reaction, a 1.2-fold excess or more of living anionic polymer relative to DPE moiety was employed to complete the reaction. Asymmetric A2A′2 and A2A′2A′′2 star-branched polystyrenes as well as A2B2 and A2B2C2 heteroarm star-branched polymers were synthesized by repeating the iteration synthetic sequence two and three times, respectively. Since the polymers obtained by each reaction stage were contaminated with their precursor polymers, they were isolated by SEC fractionation. Their high degrees of compositional, molecular weight and architectural homogeneity were confirmed by the analytical results of SEC, SLS, VPO, 1H NMR and viscosity measurements.
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