Carbon-13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with δ-titanium trichloride-diethylaluminum chloride
Carbon-13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with δ-titanium trichloride-diethylaluminum chloride
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DOI：
10.1021/ma00232a037
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发表时间：
1982-07
期刊：
影响因子：
5.5
通讯作者：
M. Kakugo;Y. Naito;K. Mizunuma;Tatsuya Miyatake
中科院分区：
文献类型：
--
作者：
M. Kakugo;Y. Naito;K. Mizunuma;Tatsuya Miyatake
通过使用14c标记的乙烯-丙烯（EP）共聚物，研究了l3C核磁共振（13C NMR）测量的准确性。由亚甲基和甲基共振计算的单体组成与放射性测定的结果一致，相对误差为4%。这些结果表明，noe是均匀的，至少对于这类碳，因此，所得的单体序列分布是足够可靠的。根据二元分布和单体进料组成计算了单体反应性比（乙烯）和r2（丙烯）。用一阶马尔可夫格式计算的三元分布与用r′和r2计算的三元分布相比较，表明乙烯倾向于交替或连续共聚的特点。采用13C NMR、1′7红外光谱、8′9和x射线衍射等手段对EP共聚物中单体序列分布进行了研究。这些研究和从共聚数据得到的单体反应性比表明，用非均相钛催化剂制备的共聚物具有广泛的共聚物组成分布。然而，尽管有这些研究，在多相催化剂存在下共聚机理的细节还没有得到充分的阐明
Theaccuracy of l3C nuclear magnetic resonance(13C NMR) measurements has been examined by using 14C-labeled ethylene-propylene (EP) copolymers. The monomer compositions calculated from the methylene and methine resonances are in agreement with those determined by radioassay within a relative error of 4%. These results indicate that the NOEs are uniform, atleast for such carbons, and, therefore, the monomer sequence distributions obtained are sufficiently reliable. Monomer reactivity ratios,(ethylene) and r2 (propylene), have been calculated from the dyad distribution and the monomer feed composition. The observed triad distribution, compared with that calculated by a first-order Markovian scheme usingr¡ and r2, shows the peculiarity that ethylene tends to copolymerize either in alternation or in runs.A number of studies on monomer sequence distribution in EP copolymershave been carried out by means of 13C NMR spectroscopy, 1" 7 infrared (IR) spectroscopy, 8’9 and X-ray diffraction. 10 These investigations and the monomer reactivity ratios obtained from copolymerization data indicate that the copolymers prepared with heterogeneous titanium catalysts have a wide copolymer composition distribution. However, despite these studies, the details of the copolymerizationmechanism in the presence of heterogeneous catalysts have not been sufficiently eluci-