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

• Published in: Macromolecules Vol. 47; no. 22; pp. 7789 - 7796
• Main Authors: Zhang, Jinjin, Xiong, Jiao, Sun, Yangyang, Tang, Ning, Wu, Jincai
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 25.11.2014
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; Ring opening polymerization; Sodium complex; Potassium complex; Aryloxy complex; Crown compound; Complex catalyst polymerization; Complex catalyst; Experimental study; Lactic acid polymer; Isotactic polymer; Stereospecificity; Stereospecific polymerization; Chemical synthesis; Catalyst activity; Crystalline structure
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma502000y

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 °C. Furthermore, the polymerization looks like an anti-Arrhenius reaction, which is slower at high temperatures than at low temperatures.