取代基效应(SCS)与乙烯-α-烯烃共聚物的序列结构Ⅲ.定量分析

本文在分析乙烯-α-烯烃共聚物序列结构时,把代表共单体反接单元的亚甲基(CH₂)βγ和γδ分别归属给了二元组VV和三元组EEV。与此同时,CH₂-δδ和δδ⁺归属给了二元组EE。表征乙烯长序列的CH₂-δ⁺δ⁺分属二元组EE和三元组EEE,对应峰强度在EE和EEE之间的分配是处理序列分布的关键。在本文中运用序列结构的Bovey关系和Randall统计进行演算,求得了修正值△的数学表达式,严格解和近似解。在规则链条件下得到的近似解与G.J.Ray的结果完全相同。当共单体含量较少时,谱峰强度Iδ⁺δ⁺的分配接近相等。在二元组和三元组的水平上,乙烯-α-稀烃共聚物的¹³C NMR谱中共有十三个峰,属于CH₂的有十个,属于CH的有三个。利用这些谱峰的强度数据可以建立一套计算公式,由此提供共聚物序列结构的全部信息。因此这是一个研究乙烯-α-烯烃共聚物序列结构的普适方法。

SUBSTITUENT CHEMICAL SHIFT (SCS) AND THE SEQUENCE STRUCTURE OF ETHYLENE-α-OLEFINE COPOLYMERS Ⅲ. Quantitative Analysis

In analysis of sequence structure of ethylenc-α-olefine copolymers methylene (CH₂) βγ and γδ which present the inverse units of comonomer in chain of the copolymer are assigned to VV dyad and EEV triad, respectively. At the same time, both CH₂ δδ and δδ⁺ are assigned to EE dyad. But partition of intensity Iδ⁺δ⁺ characterizing long sequence of ethylene between EE dyad and EEE triad is a key task for treating the sequence distribution of the copolymer. In fact, intensity Iδ⁺δ⁺ should not be divided equally. In order to revise it deduction is performed by Bovey's relationship and Randall's statistical method of polymer sequence. Therefore, the exact representation, exact and approximate solution of revisionary value A are all obtained successfully. The approximate solution obtained under condition of regular chain is identical with Ray's result. When content of comonomer in copolymer is low, the partitions of I_δ⁺δ⁺ between EE and EEE is almost equal.In level of dyad and triad, there are 13 peaks altogether on the ¹³C NMR spectrum of ethylenc-α-olefine copolymer, where 10 peaks belong to CH₂ and the other 3 to CH. A set of formula calculating sequence distribution could be proposed directly by using those intensities of peaks mentioned above. All information of copolymer sequence structure could be obtained undoubtedly based on it. Hence the method presented here is a satisfactory and universal for studying sequence structure of ethylene-α-olefine copolymers.