乙烯-己烯LLDPE的长链支链检测和<sup>13</sup> C NMR定量,Macromolecules

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乙烯-己烯LLDPE的长链支链检测和¹³ C NMR定量
Macromolecules ( IF 5.1 ) Pub Date : 2021-01-14 , DOI: 10.1021/acs.macromol.0c02619
Zhe Zhou ₁ , Clemens Anklin ₂ , Rongjuan Cong ₁ , Xiaohua Qiu ₁ , Rainer Kuemmerle ₃

Affiliation

乙烯-己烯线性低密度聚乙烯（LLDPE）由于其出色的机械性能而广泛用于包装行业。一些LLDPE包含长链分支（LCB），可改善粘弹性。因此，重要的是检测和定量LCB含量，以生产针对目标应用的改良LLDPE。¹³ C NMR是一种固有的定量方法，可以直接测量LCB。然而，乙烯-己烯LLDPE中的¹³ C NMR LCB测量存在挑战，例如在用于溶解乙烯-己烯LLDPE的常规溶剂中，乙烯-己烯-乙烯支链（EHE Br）峰与LCB次甲基峰重叠。最近有一种1-choloronaphthelane /对二氯苯-d ₄（PDCB- d₄）（9：1，w / w）溶剂的开发是为了将LCB次甲基峰与乙烯-辛烯共聚物中的乙烯-辛烯-乙烯支链（EOE Br）峰分开。在这里，我们探索使用这种溶剂在乙烯-己烯LLDPE中进行¹³ C NMR LCB测量。基于¹³在13 C NMR模拟中，可以使用400和500 MHz的10 mm NMR低温探针检测和测量低己烯含量的LLDPE中的高水平LCB（由于与EHE Br峰分离不完全而存在一些误差）。但是，低灵敏度和LCB峰与EHE Br峰重叠会给检测高己烯含量的LLDPE中的低含量LCB带来更大的困难。尽管600和700 MHz的10 mm NMR低温探针提供了更好的灵敏度以及LCB次甲基峰与EHE Br峰的出色分离，但LCB次甲基峰与EHE Br峰的低场¹³ C卫星重叠。因此，开发了一种新的抗不可思议的自然丰度双量子转移实验（anti-INADEQUATE）逆门控NMR脉冲序列ainadigsp1d.2，以去除^13个C卫星峰并量化乙烯-己烯LLDPE中的LCB含量。通过这种新的NMR脉冲序列获得的LCB结果与预期值非常吻合。

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Long-Chain Branch Detection and Quantification in Ethylene–Hexene LLDPE with 13C NMR

Ethylene–hexene linear low-density polyethylene (LLDPE) is widely used in the packaging industry due to its outstanding mechanical properties. Some LLDPEs contain long-chain branching (LCB), which improves viscoelastic properties. Therefore, it is important to detect and quantify LCB content to enable production of improved LLDPEs for targeted applications. ¹³C NMR is an intrinsically quantitative method and can measure LCB directly. However, ¹³C NMR LCB measurement in ethylene–hexene LLDPE has challenges, such as the overlap of the ethylene–hexene–ethylene branch (EHE Br) peak with the LCB methine peak in conventional solvents used for dissolving ethylene–hexene LLDPE. Recently a 1-choloronaphthelane/para-dichlorobenzene-d₄ (PDCB-d₄) (9:1, w/w) solvent was developed to separate the LCB methine peak from the ethylene–octene–ethylene branch (EOE Br) peak in an ethylene–octene copolymer. Here, we explore using this solvent for ¹³C NMR LCB measurement in ethylene–hexene LLDPE. Based on ¹³C NMR simulation, a high level of LCB in low hexene content LLDPE might be detected and measured (with some errors due to incomplete separation from the EHE Br peak) with 400 and 500 MHz 10 mm NMR cryoprobes. However, low sensitivity and LCB peak overlap with the EHE Br peak pose even more difficulties for detecting the low level LCB in high hexene content LLDPE. Although 600 and 700 MHz 10 mm NMR cryoprobes provide much better sensitivity and excellent separation of the LCB methine peak from the EHE Br peak, the LCB methine peak overlaps with the EHE Br peak’s downfield ¹³C satellite. Therefore, a new anti-incredible natural-abundance double-quantum transfer experiment (anti-INADEQUATE) inverse-gated NMR pulse sequence, ainadigsp1d.2, was developed to remove ¹³C satellite peaks and quantify LCB content in ethylene–hexene LLDPE. The LCB results obtained with this new NMR pulse sequence are in very good agreement with expected values.

更新日期：2021-01-26

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