Living Anionic Polymerization of 4-(α-Alkylvinyl)styrene Derivatives

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• 作者：Kenji Sugiyama ; Kenji Watanabe ; Akira Hirao ; Mayumi Hayashi
• 刊名：Macromolecules
• 出版年：2008
• 出版时间：June 24, 2008
• 年：2008
• 卷：41
• 期：12
• 页码：4235 - 4244
• 全文大小：159K
• 年卷期：v.41,no.12(June 24, 2008)
• ISSN：1520-5835

文摘

The anionic polymerizations of four new 4-(α-alkylvinyl)styrene derivatives have been studied under various conditions. These monomers involve 4-(α-ethylvinyl)styrene (2), 4-(α-butylvinyl)styrene (3), 4-(α-isopropylvinyl)styrene (4), and 4-(α-tert-butylvinyl)styrene (5). Among them, the α-tert-butyl derivative, 5, was found to undergo selective living anionic polymerization under the conditions in THF at −78 °C as well as in benzene at 25 °C to afford remarkably stable living polymers. The resulting polymers possessed well-controlled molecular weights (M_n ~ 80 000 g/mol) and narrow molecular weight distributions (M_w/M_n < 1.05) as well as an α-tert-butylvinyl group in all monomer units. On the other hand, the carefully selected conditions are required to achieve the living anionic polymerization of 2, 3, and 4. They could undergo selective living anionic polymerization in THF at −78 °C with use of oligo(α-methylstyryl)potassium as an initiator. In contrast, the living anionic polymerizations of such monomers were not successful under the conditions with sec-BuLi in THF at −78 °C and in benzene at 25 °C. Considering the detailed polymerization results, the stability of chain-end carbanions substituted with 4-α-alkylvinyl groups were observed to increase in the following order: living poly(2) ~ living poly(3) < living poly(4) ≪ living poly(5). This is exactly the same order as those of electron-donating ability and steric bulkiness of the α-substituent, and accordingly, such factors may possibly play an essential role to achieve the selective living polymerization of 4-(α-alkylvinyl)styrene derivatives. The three polymer reactions of poly(4-(α-alkylvinyl)styrene) with m-chloroperoxybenzoic acid, bromine, and sec-BuLi were performed in order to transform the pendant α-alkylvinyl groups into the corresponding epoxide, bromide, and carbanionic species. These reactions were found to proceed cleanly and quantitatively to afford the new functional polymers possessing the above reactive groups in all monomer units and well-defined structures originated from the base polymer.