Electron rich salen-AlCl catalysts as efficient initiators for the ring-opening polymerisation of rac-lactide
Electron rich salen-AlCl catalysts as efficient initiators for the ring-opening polymerisation of rac-lactide
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DOI：
10.1016/j.eurpolymj.2019.07.017
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发表时间：
2019-10-01
影响因子：
6
通讯作者：
Garden, Jennifer A.
中科院分区：
文献类型：
--
作者：
Gaston, Anand J.;Navickaite, Gabija;Garden, Jennifer A.
丙交酯的开环聚合是制备具有良好控制的聚合物结构和定制材料性能的生物可降解材料的有用方法。虽然均相配体-Al-OR配合物在该领域取得了巨大成功，但配体-AlCl配合物的引发却落后了。在这里，我们报道了四种具有NEt2-取代基的新型salen-AICI配合物，它们通过用一当量的环氧丙烷原位活化，对外消旋丙交酯开环聚合（k(obs) < 1.9 x 10(-3) s(-1)）表现出高催化活性。将路易斯碱性NEt2基团引入配体支架中不仅提高了引发效率，而且避免了对路易斯碱性助催化剂和过量环氧化物的需要。值得注意的是，对我们的氨基取代催化剂的研究表明，六配位铝酸盐物质的形成可能会阻碍而不是增强催化活性。
The ring-opening polymerisation of lactide is a useful means to prepare biodegradable materials with well controlled polymer architectures and bespoke material properties. While homogeneous ligand-Al-OR complexes have shown great success in this field, initiation from ligand-AlCl complexes has lagged behind. Here, we report four new salen-AICI complexes featuring NEt2-substituents, which display high catalyst activities towards rac-lactide ring-opening polymerisation (k(obs) < 1.9 x 10(-3) s(-1)) via in situ activation with a single equivalent of propylene oxide. Incorporating Lewis basic NEt2 groups into the ligand scaffold not only improves the initiation efficiency but also avoids the need for a Lewis basic co-catalyst and excess epoxide. Notably, studies of our amino-substituted catalysts reveal that the formation of a hexacoordinate aluminate species may hinder rather than enhance catalytic activity.