Ring-Opening Copolymerizaton of Cyclohexene Oxide and Succinic Anhydride by Zinc and Magnesium Schiff-Base Complexes Containing Alkoxy Side Arms.,Inorganic Chemistry

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Ring-Opening Copolymerizaton of Cyclohexene Oxide and Succinic Anhydride by Zinc and Magnesium Schiff-Base Complexes Containing Alkoxy Side Arms.
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2020-05-14 , DOI: 10.1021/acs.inorgchem.0c00839
Arnut Virachotikul ₁ , Nattiya Laiwattanapaisarn ₁ , Phonpimon Wongmahasirikun ₁ , Parichat Piromjitpong ₁ , Kittipong Chainok ₂ , Khamphee Phomphrai _{1,

3}

Affiliation

The ring-opening copolymerization (ROCOP) of epoxides and cyclic anhydrides is a promising method for the synthesis of new polyesters with various polymer properties. Among previously reported metal catalysts for ROCOP, the Schiff-base complexes have gained significant attention because of their ease of synthesis and modification. In this work, zinc and magnesium complexes containing Schiff-base ligands with different alkoxy side arms [−(CH₂)₂O– and −(CH₂)₃O−] were synthesized and shown to have a cubane metal core by X-ray crystal structures. All complexes were studied in the ROCOP of cyclohexene oxide (CHO) and succinic anhydride (SA) in toluene at 110 °C. The zinc complex having a shorter side arm is the most active catalyst for copolymerization, giving poly(CHO-alt-SA) with narrow dispersity and negligible ether linkage. On the other hand, magnesium complexes were not active because of the formation of stable carboxylate species. The detailed analysis of polyester obtained from zinc complexes unexpectedly revealed three different types of polymer structures occurring at different polymerization times. Cyclic polymer was generated at the beginning by intramolecular transesterification of the alkoxy side arm, giving a low-molecular-weight polyester. At higher conversion, cyclization diminished, giving just a linear polyester but with minor competitive formation of higher-molecular-weight polyester having cyclohexanediol as an end group. On the basis of a thorough understanding of the polymerization mechanism, the desired cyclic poly(CHO-alt-SA) was successfully synthesized using a low monomer/catalyst ratio.

中文翻译：

含烷氧基侧臂的锌和镁席夫碱配合物的环己烯氧化物和琥珀酸酐的开环共聚合。

环氧化物和环状酸酐的开环共聚（ROCOP）是合成具有各种聚合物特性的新型聚酯的一种有前途的方法。在先前报道的用于ROCOP的金属催化剂中，席夫碱配合物由于易于合成和修饰而受到了广泛关注。在这项工作中，锌和镁配合物包含具有不同烷氧基侧臂[-（CH ₂）₂ O-和-（CH ₂）_3的席夫碱配体合成了O-]，并通过X射线晶体结构显示了具有古巴金属核。在110°C下，在甲苯中的环己烯氧化物（CHO）和琥珀酸酐（SA）的ROCOP中研究了所有配合物。锌配合物具有较短侧臂被共聚最活跃的催化剂，得到聚（CHO- ALT-SA），分散性窄，醚键可忽略不计。另一方面，镁配合物由于形成稳定的羧酸盐物种而没有活性。从锌络合物获得的聚酯的详细分析出乎意料地揭示了在不同聚合时间出现的三种不同类型的聚合物结构。在开始时，通过烷氧基侧臂的分子内酯交换反应生成环状聚合物，得到低分子量聚酯。在较高的转化率下，环化作用减弱，仅得到线性聚酯，而竞争性地形成了以环己二醇为端基的高分子量聚酯。在充分了解聚合机理的基础上，所需的环状聚（CHO-盐-SA）是使用低单体/催化剂比率成功合成的。

更新日期：2020-07-06

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