Highly diheterotactic polymerization of tert-butyl crotonate
Highly diheterotactic polymerization of tert-butyl crotonate
复制标题
巴豆酸叔丁酯的高度二杂规聚合
DOI：
10.1021/ma951275f
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发表时间：
1996
期刊：
影响因子：
5.5
通讯作者：
K. Hatada
中科院分区：
文献类型：
--
作者：
K. Ute;and Takeshi Asada;K. Hatada
丁酸叔丁酯与RMgBr或r2mg （R: t- c4h9, c6h5）在甲苯中聚合得到立体规整性高的聚合物。特别是（c6h5） 2mg引发剂效率高，可用于制备适合于立体结构分析的低聚物。通过酯交换反应将巴豆酸叔丁酯的低聚物转化为巴豆酸甲酯的低聚物，并通过GPC和超临界流体色谱将低聚物分离为1mer到10mer的单体同源物。1h NMR表明，每个低聚物同源物主要由两个非对映体A和b组成。通过x射线单晶分析，6mer-A、7mer-A、8mer-A和7mer-B的构型序列分别为et(ettt) 2、et(ettt) 2、et(ettt) 3和（ettt） 3，其中e和t分别表示二聚体和三聚体。因此，这种聚合对ettt结构具有高度的立体特异性。ettt结构很好地解释了这种立体规则聚丁酸叔丁酯的α-CH、β-CH、β-CH 3和t- c4h9o基团在核磁共振信号中的不等效性。由一et五聚体的规则重复组成的聚合物链在α-和β-位置上可视为双异规序列，因此这种新型的立体规则聚合物结构应称为双异规聚合物。
The polymerization of tert-butyl crotonate with RMgBr or R 2 Mg (R : t-C 4 H 9 , C 6 H 5 ) in toluene gave a polymer with high stereoregularity. In particular, (C 6 H 5 ) 2 Mg had high initiator efficiency and was useful for the preparation of oligomer suitable for stereostructure analysis. The oligomer of tert-butyl crotonate was transformed into oligo(methyl crotonate) by transesterification, and the oligo(methyl crotonate) was fractionated into the individual homologues from 1mer to 10mer by means of GPC and supercritical fluid chromatography. 1 H NMR spectroscopy showed that each oligomer homologue consisted essentially of two diastereomers A and B. The configurational sequences for 6mer-A, 7mer-A, 8mer-A, and 7mer-B were determined by X-ray single crystal analysis to be et(ettt) 2 , et(ettt) 2 et, et(ettt) 3 , and (ettt) 3 , respectively, where e and t denote erythro and threo diads. Accordingly, this polymerization is highly stereospecific to ettt structure. The ettt structure well explains the nonequivalence in the NMR signals due to each α-CH, β-CH, β-CH 3 , and t-C 4 H 9 O group of this stereoregular poly(tert-butyl crotonate). The polymer chain consisting of regular repetition of an ettt pentad can be regarded as a double heterotactic sequence with respect to the α- and β-positions, and therefore this novel structure of stereoregular polymer should be termed diheterotactic.