用IR、~1H和~(13)C-NMR研究聚戊二烯-1,3结构

用IR、~1H和~(13)C-NMR方法研究了环烷酸钕催化聚戊二烯-1,3的链节结构和序列分布。结果表明,聚合物含有约70％顺-1,4,25％反-1,2和5％反-1,4结构。确定了计算脂肪碳~(13)C-NMR化学位移的一组经验参数,对各峰做了归属。~(13)C-NMR能很好地辨别顺-1,4,反-1,4和反-1,2等各种结构,发现稀土催化聚戊二烯-1,3单体链节是以头-尾相联,不存在反结,并发现了1,4-1,2联结的序列。

STRUCTURAL STUDY OF POLYPENTADIENE WITH IR, 1H AND 13C-NMR SPECTROSCOPY

The microstructure and monomer sequence distribution of polypentadiene-1, 3 obtained with naphthenate neodymium catalyst have been examined by IR, 1H and 13C-NMR spectroscopy. The results show that 1, 3-pentadiene enters in polymer chain predomin nantly as cis-1, 4 unit (70% mole) and trans-1, 2 (25% mole) with minor fraction of trans-1, 4 units (5% mole). Based on our new set of empirical parameters for calculating chemical shifts, the assignment of carbons in the aliphatic region of 13C-NMR spectra has been given. Thus cis-1, 4, trans-1, 4 and trans-1, 2 units-and sequences of monomers can be identified by 13C-NMR spectroscopy. It is found that monomer units of the polypentadiene-1, 3 exist only in head-to-tail structure without any head-to-head or tail-to-tail structure. Sequence of 1, 4-1, 2 has been also observed. In addition, we have measured the spin lattice relaxation times (T1) for carbons of cis-1, 4 units.