A GPC study of the stereoselective polymerization of methyloxirane catalyzed by a solution of single crystal of [Zn(OCH3)2·(C2H5ZnOCH3)6]
A GPC study of the stereoselective polymerization of methyloxirane catalyzed by a solution of single crystal of [Zn(OCH3)2·(C2H5ZnOCH3)6]
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DOI：
10.1002/macp.1978.021790922
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发表时间：
1978-09
影响因子：
2.5
通讯作者：
M. Ishimori;T. Hagiwara;T. Tsuruta
中科院分区：
文献类型：
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作者：
M. Ishimori;T. Hagiwara;T. Tsuruta
据报道，用由二乙基锌和醇组成的二元催化剂体系进行甲基环氧乙烷聚合的引发剂是二烷氧基锌，后者的活性明显取决于烷氧基相对于锌原子的排列方式。在迄今为止报道的各种环氧乙烷聚合催化剂中，二乙基锌/甲醇体系是特别令人感兴趣的，因为甲基环氧乙烷与该体系的聚合通过对映异构催化剂位点控制机理进行，类似于I-烯烃与齐格勒-纳塔催化剂的聚合以得到全同立构聚合物。该机理被认为涉及对称分布在活性二甲醇锌中的手性位点，表示为d-和I-位点，其中d-位点优先与D-甲基环氧乙烷反应，而与生长的聚合物链端的构型无关，I-位点优先与L-甲基环氧乙烷反应。关于催化剂位点的手性（或对映体）结构，几乎没有可用的信息，因为活性二甲醇锌是无定形粉末状物质，并且二甲醇锌作为催化剂的效率极低。
It has been reported that the initiator for methyloxirane polymerization with a binary catalyst system consisting of diethylzinc and alcohol is zinc dialkoxide’), and that the activity of the latter is remarkably dependent upon the mode of arrangement of alkoxy-groups with respect to the zinc atoms’). Among a variety of oxirane polymerization catalysts so far reported, the diethylzinc/methanol system is of particular interest because the polymerization of methyloxirane with this system proceeds by an enantiomorphic catalyst sites control mechanism3-’I, analogous to the polymerization of I-alkene with Ziegler-Natta catalyst to give isotactic polymer6.’). This mechanism is assumed to involve the chiral sites denoted as d-and I-sites distributed symmetrically in the active zinc dimethoxide, where the d-sites preferentially react with D-methyloxirane regardless of the configuration of the growing polymer chain end and the I-sites with L-methyloxirane.Although the elucidation of the stereocontrol mechanism of the methyloxirane polymerization has progressed extensively for these several years, there has been available little information concerning the chiral (or enantiomorphic) structure of the catalyst sites, because the active zinc dimethoxide is an amorphous powdery substance and the efficiency of zinc dimethoxide as a catalyst is extremely low”.