Successive Synthesis of Well-Defined Star-Branched Polymers by a New Iterative Approach Involving Coupling and Transformation Reactions
2005; American Chemical Society; Volume: 38; Issue: 11 Linguagem: Inglês
10.1021/ma050248e
ISSN1520-5835
AutoresTomoya Higashihara, Masato Nagura, Kyoichi Inoue, Naoki Haraguchi, Akira Hirao,
Tópico(s)Organometallic Complex Synthesis and Catalysis
ResumoSuccessive synthesis of well-defined star-branched polymers has been successfully achieved by a new iterative methodology based on living anionic polymerization. The methodology involves only two sets of reaction conditions for the entire iterative reaction sequence: (a) a coupling reaction of the benzyl bromide-functionalized polymer with poly(substituted styryl)lithium end-capped with 1-(3-tert-butyldimethylsilyloxymethylphenyl)-1-phenylethylene to link two polymer chains and introduce 3-tert-butyldimethylsilyoxymethylphenyl group(s) of benzyl bromide precursor(s) and (b) a transformation reaction of the introduced precursor(s) into benzyl bromide functionality (functionalities) by treatment with (CH3)3SiCl−LiBr. By repeating these two reactions, an array of asymmetric star-branched polymers were successively synthesized. They involved 3-arm ABC, 4-arm ABCD and A2B2, and 6-arm A2B2C2 stars whose A, B, C, and D segments are polystyrene, poly(α-methylstyrene), poly(4-methylstyrene), poly(methyl methacrylate), or poly(tert-butyl methacrylate), respectively. Their high degrees of compositional, molecular weight, and architectural homogeneity as well as narrow molecular weight distributions (Mw/Mn < 1.05) were confirmed by the analytical results of SEC, 1H NMR, VPO, and SLS. The poly(tert-butyl methacrylate) segments of the A2B2C2 star-branched polymer were readily and quantitatively hydrolyzed under the acidic conditions. As a result, a new ionic A2B2C2 star having poly(methacrylic acid) segments was obtained.
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