~(13)C核磁共振研究稀土催化剂聚合双烯的机理

用~(13)C-NMR 方法测定了稀土顺丁二烯和聚异戊二烯链端结构及序列结构,从链端结构推测的聚合活性链端结构与前文是一致的。在聚异戊二烯中存在着“头-头”和“尾-尾”结构,这种结构引起活性链端甲基位置的改变,从而解释了稀土异戊二烯中3,4-链节的形成。测定了不同聚合温度对聚合物中顺、反结构含量的影响,可用活性链端的 anti-syn异构化加以解释。

STUDY ON THE MECHANISM OF D1ENE POLYMERIZATION BASED ON THE RARE EARTH CATALYSTS WITH 13C-NMR

The structures of polybutadiene and polyisoprene obtained by NdCl3-C2H5OH-AlEt3 catalyst have been investigated with 13C-NMR method. According to the data of chemical shift, the configuration of terminal η3-allylit growing chain is predominated by "tail-to-head" linkage. The temperature of polymerization may change cis-1,4 polymer content. This can be explained by isomerization between anti- and syn-η3-allyl. Since there is a small amount of "head-head" and "tail-tail" linkages in the polyisoprene, 3,4-unit formation in the polyisoprene can be realized.