Development of an Arylthiobismuthine Cocatalyst in Organobismuthine-Mediated Living Radical Polymerization: Applications for Synthesis of Ultrahigh Molecular Weight Polystyrenes and Polyacrylates

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• 作者：Eiichi Kayahara ; Shigeru Yamago*
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：February 25, 2009
• 年：2009
• 卷：131
• 期：7
• 页码：2508-2513
• 全文大小：234K
• 年卷期：v.131,no.7(February 25, 2009)
• ISSN：1520-5126

文摘

Diphenyl(2,6-dimesitylphenylthio)bismuthine (1a) serves as an excellent cocatalyst in organobismuthine-mediated living radical polymerization (BIRP). Both low and high molecular weight polystyrenes and poly(butyl acrylate)s (PBAs) with controlled molecular weights and low polydispersity indexes (PDIs) were synthesized by the addition of a catalytic amount of 1a to an organobismuthine chain-transfer agent, methyl 2-dimethylbismuthanyl-2-methylpropionate (3). The number-average molecular weight (M_n) of the resulting polymers increases linearly with the monomer/3 ratio. Structurally well-defined polystyrenes with M_n’s in the range from 1.0 × 10⁴ to 2.0 × 10⁵ and PDIs of 1.07−1.15 as well as PBAs with M_n’s in the range from 1.2 × 10⁴ to 2.8 × 10⁶ and PDIs of 1.06−1.43 were successfully prepared under mild thermal conditions. Control experiments suggested that 1a reversibly reacts with the polymer-end radical to generate an organobismuthine dormant species and 2,6-dimesitylphenylthiyl radical (2a). This reaction avoids the occurrence of chain termination reactions involving the polymer-end radicals and avoids undesired loss of the bismuthanyl polymer end group. The bulky 2,6-dimesitylphenyl group attached to the sulfur atom may prevent the addition of thiyl radicals to the vinyl monomers to generate new polymer chains.