共轭二烯烃的Ziegler─Natta催化聚合

Polymerization of Conjugated Dtenes by Ziegler-Natta Catalysts

共轭二烯烃的聚合是配位阴离子聚合，双金属配合物是聚合的活性中心，控制单体的构象是控制聚合物结构的关键。单体在低值配位场稳定化能（ＬＦＳＥ）过渡金属离子，如Ｃｏ^（２＋）、Ｔｉ^（３＋）上螯合，螯合单体具有顺式构象，所得聚合物具有顺１，４结构；在中等ＬＦＳＥ的过渡金属离子，如Ｖ^（３＋）、Ｃｒ^（３＋）上配位，配位单体具有反式构象，所得聚合物具有反１，４结构或是１，２聚合物；高ＬＦＳＥ值过渡金属离子不易控制活性价态，双金属配合物不够稳定，所得聚合物分子量常较低，结构规整性也常不够理想。

The polymerization of conjugated dienes by Ziegler-Natta catalysts is studied.It is believed that the active centers of the catalysts are the bimetallic complexes composed of transition metal and organo-aluminum compounds,through lonic chlorine and alkyl or alkyl chain endings Controlling the conformation of monomer inserting to the chain ending is of great importance:by chelation of both the double bonds of the monomer with cisoid of conformation on transition metal ions of low ligand field stabilization energy (LFSE),cis1, 4 polymers are obtained,and by coordination of only one double bond with transoid conformation,on transition metal irons of higher LFSE,trans 1,4 or 1, 2 polymers will be prepared.