多核Nd-Al双金属配合物对丁二烯的聚合——Ⅰ.聚合物的分子量与微观结构间的关系及其聚合机理的讨论

在从均相稀土催化剂中分离出有聚合活性的Nd-Al双金属配合物的基础上,利用该配合物可单独引发丁二烯聚合的特点,较详细地研究了活性体浓度,外加烷基铝浓度,单体浓度以及聚合温度等因素对聚合产物分子量及微观结构的影响,确认二者之间存在着一定的内在联系,即分子量越高,顺式含量也越高;反之,分子量越低,顺式含量也越低。对此,本文提出了增长链对聚合过程起反作用的观点,从聚合机理的角度给予了解释。

BUTADIENE POLYMERIZATION CATALYZED BY POLYNUCL-EAR Nd-Al BIMETALLIC COMPLEX I. Relationship between Molecular Weight and Microstructure and Discussion of Polymerization Mechanism

Based on the successful isolation of polynuclear Nd-Al bimetallic complex which alone can initiate diene polymerization without the presence of the co-catalyst trialkyl aluminium, the effects of active speecies, additional trialkyl aluminium, and monomer concentrations as well as temperature on butadiene polymerization were studied in detail. The results indicate that there is a relationship between the molecular weight and the microstructure of obtained polybutadiene, that is, the lower the molecular weight, the lower the cis-1,4 content and the higher the trans-1,4 content. To explain the experimental results, a new view which involves the reaction of the propagating polymer chain on polymerization process was put forward and some explanation according to syn-anti isomerization of n-allyl mechanism was given.