Highly Iso-Selective and Active Catalysts of Sodium and Potassium Monophenoxides Capped by a Crown Ether for the Ring-Opening Polymerization of rac-Lactide

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• 作者：Jinjin Zhang ; Jiao Xiong ; Yangyang Sun ; Ning Tang ; Jincai Wu
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：November 25, 2014
• 年：2014
• 卷：47
• 期：22
• 页码：7789-7796
• 全文大小：358K
• ISSN：1520-5835

文摘

Sodium and potassium complexes supported by a bulky monophenoxy with one xanthenyl group at the ortho-position and 18-crown-6 or 15-crown-5 as an auxiliary ligand were synthesized and characterized. These complexes are highly iso-selective and active catalysts for the controlled ring-opening polymerization of rac-lactide. The best isotacticity (P_m) achieved was 0.86, which is the highest iso-selectivity reported to date for an alkali-metal complex. In addition, the corresponding polymer exhibited a high T_m of 182 掳C. Furthermore, the polymerization looks like an anti-Arrhenius reaction, which is slower at high temperatures than at low temperatures.