Acta Chimica Sinica ›› 2012, Vol. 70 ›› Issue (13): 1488-1495.DOI: 10.6023/A12030010 Previous Articles     Next Articles



王世海, 阳年发, 杨利文, 龚行   

  1. 湘潭大学化学学院 环境友好化学与应用省部共建教育部重点实验室 湘潭 411105
  • 投稿日期:2012-03-18 发布日期:2012-06-01
  • 通讯作者: 阳年发
  • 基金资助:

    项目受国家自然科学基金(Nos. 20972131, 20772102)资助.

Synthesis of Several Chiral Atom Transfer Radical Polymerization Initiators and Its Helix-sense-selective Initiating Function for ATRP

Wang Shihai, Yang Nianfa, Yang Liwen, Gong Hang   

  1. Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, College of Chemistry, Xiangtan University, Xiangtan, Hunan 411105, China
  • Received:2012-03-18 Published:2012-06-01
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Nos. 20972131, 20772102).

Five optically active alkyl bromides were synthesized and were used as chiral atom transfer radical polymerization (ATRP) initiators for the helically selective polymerization of 1-phenyldibenzosuberyl methacrylate (PDBSMA). In order to avoid the racemization of the primary free radical formed in initiating step, the optically active alkyl bromide initiators were designed as such a structure in which the bromine atom did not connect to the chiral center. The chiral ATRP initiators tested here are (S)-2,2'-di(bromomethyl)-1,1'-binaphthyl, (S)-2-bromomethyl-2-methyl-1,1'-binaphthyl, menthyl α-bromophenylacetate, N-menthyl α-bromophenylacetamide and (3β,5α)-cholestan-3-yl α-bromo phenylacetate. (S)-2,2'- Di(bromomethyl)-1,1'-binaphthyl, (S)-2-bromomethyl-2-methyl-1,1'-binaphthyl and menthyl α-bromophenylacetate were synthesized following the method reported by literatures. N-menthyl α-bromophenylacetamide was synthesized by adding dropwise the solution of α-bromophenylacetyl chloride in tetrahydrofuran (THF) into the mixture of menthylamine, triethylamine and THF with stirring at room temperature within 3 h and stirring at room temperature for another 8 h after the addition. (3β,5α)-Cholestan-3-yl α-bromo phenylacetate was synthesized using the method for the synthesis of menthyl α-bromophenylacetate except using (3β,5α)-cholestanol instead of menthol. The poly-PDBSMA obtained from the ATRP initiated by the optically active alkyl bromides was fractionated into THF-soluble part and THF-insoluble part. THF-soluble part was optically active. By studying the chiroptical properties of the THF-soluble part of the poly-PDBSMA and by comparing the optical rotation of the THF-soluble part of the poly-PDBSMA with that of the poly(methyl methacrylate) (poly-MMA) obtained under the same polymerization condition, we concluded that the ATRP initiated by the optically active alkyl bromides was helix-sense selective. The NMR study of poly-MMA derived from the THF-insoluble part showed that the polymer produced from the polymerization initiated by (S)-2,2'-di(bromomethyl)-1,1'-binaphthyl was isotactic, which proved further that the ATRP initiated by the optically alkyl bromines was helix-sense selective. Among the five optically active alkyl bromides, (S)-2,2'-di(bromomethyl)-1,1'-binaphthyl and (S)-2-bromomethyl-2-methyl-1,1'-binaphthyl had the best helical selectivity. The helix-sense selectivity depended on the polymerization temperature. The ceiling temperature is 70 ℃. In the range of 0-70 ℃, the helix-sense selectivity increased with the increase of the polymerization temperature.

Key words: atom transfer radical polymerization, chiral alkylbromide, helix-sense-selective, helical polymer