用^(13)C核磁共振测定高聚物分子量——PE分子量的测定

Molecular Weight Determination of Polyethylenes With ^(13)C FT NMR Method——Measurements of Mn in PE

提出应用^(13)C核磁共振(NMR)方法测定聚合物分子链末端浓度来求数均分子量M_n的问题。具有不同分子量的聚乙烯(PE)在^(13)C-NMR谱上,主链亚甲碳原子,各种支化链结构以及接近链末端和末端的碳原子将显示出各自的不同强度的特征峰。考虑了影响^(13)C-NMR谱定量性的因素,通过谱强度计算出一系列经分级后PE各级分的数均分子量M_n,与GPC的测定结果基本一致,探讨了^(13)C谱测定M_n的可能性和准确性。

A C-13 FT NMR Method to determine the number average molecular veight (Mn) of polyethylenes (PE) with monitoring terminal groups is suggested and described. For PE with different Mn, its main chain (CH_2)_n, each chain branches and terminal groups give rise to a unique array of resonances.If the influence of T_(1c) and NOE on quantitative analysis of C-13 NMR spectra is properly considered, each resonance intensity is directly proportional to the number of contributing carbon atoms. Thus Mn of several fractions with different molecular weight of PE is calculated from its resonance intensity obtained by C-13 NMR spectra. These results are consistent vith Mn measured by a GPC method. It is investigated The feasibility and accuracy of determininy Mn of PE by C-13 NMR method have been investigated.