揭示使用 N-杂环烯烃制备的聚醚共聚物的单体梯度：无金属阴离子与两性离子路易斯对聚合,Macromolecular Chemistry and Physics

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揭示使用 N-杂环烯烃制备的聚醚共聚物的单体梯度：无金属阴离子与两性离子路易斯对聚合
Macromolecular Chemistry and Physics ( IF 2.5 ) Pub Date : 2023-05-19 , DOI: 10.1002/macp.202300097
Erik Kersten ₁ , Olga Linker _{1,

2} , Jan Blankenburg _{1,

2} , Manfred Wagner ₃ , Patrick Walther ₄ , Stefan Naumann ₄ , Holger Frey ₁

Affiliation

详细研究了基于N-杂环烯烃 (NHO) 的环氧乙烷 (EO) 和环氧丙烷 (PO) 共聚的聚合途径。采用原位¹ H NMR 光谱，对有机催化阴离子聚合装置（系统 A）和两性离子路易斯对型方法（系统 B）进行了比较研究。将获得的动力学数据拟合到非终端模型（Jaacks 和 Ideal Integrated）和终端 Mayo-Lewis 模型（Meyer Lowry）以确定反应率，揭示了共聚醚微观结构和可达到的摩尔质量的显着差异。而对于无金属催化（系统 A），r _EO = 3.4 和r _{PO的反应率} 发现= 0.30，表明软梯度结构，Mg(HMDS) ₂（系统B）的存在仅需要两性离子传播。这导致选择性增强，显示出相应的参数r _EO = 7.9 和r _PO = 0.13，与所提出的单体激活机制一致。块状强锥形共聚醚微观结构也反映在热性能中，显示出后一种样品的熔点和更高的摩尔质量（M _n >50 000 g mol ^-1）。值得注意的是，这项研究不仅确定了 EO/PO 的有效聚合体系，而且还强调了通过原位¹可以快速可靠地阐明有关聚合机理的 H NMR 动力学关键问题，从而简化对基本结构-性能关系的了解。

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Revealing the Monomer Gradient of Polyether Copolymers Prepared Using N-Heterocyclic Olefins: Metal-Free Anionic versus Zwitterionic Lewis Pair Polymerization

N-Heterocyclic olefin (NHO)-based polymerization pathways for the copolymerization of ethylene oxide (EO) and propylene oxide (PO) are investigated in detail. Employing in situ ¹H NMR spectroscopy, both an organocatalytic, anionic polymerization setup (system A) and a zwitterionic, Lewis pair-type approach (system B) are studied comparatively. The obtained kinetics data are fitted to the non-terminal model (Jaacks and Ideal Integrated) and terminal Mayo–Lewis model (Meyer Lowry) to determine the reactivity ratios, revealing striking differences in copolyether microstructure and achievable molar masses. While for the metal-free catalysis (system A) reactivity ratios of r_EO = 3.4 and r_PO = 0.30 are found, indicating a soft gradient structure, the presence of Mg(HMDS)₂ (system B) entails exclusively zwitterionic propagation. This results in enhanced selectivity, displaying corresponding parameters of r_EO = 7.9 and r_PO = 0.13, in line with the proposed monomer-activated mechanism. The block-like, strongly tapered copolyether microstructure is also reflected in the thermal properties, showing a melting point for the latter sample and much higher molar masses (M_n >50 000 g mol⁻¹). Notably, this study not only identifies capable polymerization systems for EO/PO, but also underlines that via in situ ¹H NMR kinetics key questions regarding the polymerization mechanism can be illuminated quickly and reliably, simplifying access to essential structure-property relations.

更新日期：2023-05-19

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