无规丁苯共聚物的核磁共振波谱——二单元序列结构的定量计算

在前文谱带指认的基础上,用¹³C-NMR谱的脂肪碳部分计算了无规丁苯共聚物中十六种二单元的组成.由它们推出的四种结构单元的组成与从氢谱得到的结果相符.在本聚合体系下,二单元的序列长度和四种结构单元的平均持续比表明,苯乙烯单元(S)易形成短嵌段聚合物,1,2-丁二烯单元(v)显示出易与其它三种单体单元结合的趋势,反式1,4-丁二烯单元(t)和顺式1,4-丁二烯单元(c)除形成本身的嵌段聚合物以外,也易形成交替式结构.结果表明,¹³C-NMR是研究丁苯共聚物微观结构的有力工具.

NMR SPECTRA OF RANDOM BUTADIENE-STYRENE COPOLYMER QUANTITATIVE CALCULATION OF DIAD SEQUENCE STRUCTURE

The compositions of sixteen diads of random butadiene -styrcne copolymers were calculated by using aliphatic carbon portion of the 13C-NMR spectra, based on the assignment in the previous paper. Compositions of the four monomer units deduced from the calculation were consistent with the results obtained from 1H-NMR spectra. In the polymerization system, the average sequence lengths of diads and the average permanence ratio of four monomer units indicate that the styrcne unit (S) tends to form short block polymers, vinyl unit (v) shows a tendency to combine with the other three monomer units, trans- 1, 4-butadiene unit (t) and cis-1, 4-butadiene unit (c) show tendency to form structures containing alternating units besides the block polymers formed from themselves. The results prove that 13C-NMR is a powerful tool for investigating the microstructure of butadiene-styrcne copolymers.