Copolymerization of 蔚-Caprolactone and l-Lactide Catalyzed by Multinuclear Aluminum Complexes: An Immortal Approach

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• 作者：Lei Li ; Bo Liu ; Dongtao Liu ; Chunji Wu ; Shihui Li ; Bo Liu ; Dongmei Cui
• 刊名：Organometallics
• 出版年：2014
• 出版时间：November 24, 2014
• 年：2014
• 卷：33
• 期：22
• 页码：6474-6480
• 全文大小：413K
• ISSN：1520-6041

文摘

A series of aluminum complexes L^aAl₂Me₄ (1), L^b₂Al₄Me₄ (2), and L^cAl₂Me₄ (3) have been prepared from the reaction of AlMe₃ with Salan- and Salen-type ligands (L^aH₂ = [2-OH-3,5-^tBu₂-C₆H₂CH₂N(CH₃)]₂-(m-phenylene); L^bH₄ = [2-OH-3,5-^tBu₂-C₆H₂CH₂NH]₂-(m-phenylene); L^cH₂ = [2-OH-3,5-^tBu₂-C₆H₂CH鈺怤]₂-(m-phenylene)), respectively. All these complexes were characterized by NMR spectroscopy, X-ray diffraction, and elemental analyses, with complexes 1 and 3 adopting binuclear structures, while complex 2 being tetranuclear. In the presence of alcohol, the binuclear complexes 1 and 3 catalyzed controlled ring-opening homopolymerizations of both 蔚-CL and l-LA. In the copolymerization experiments, complexes 1 and 2 produced tapered copolymers of 蔚-CL and l-LA, while complex 3 was able to provide 蔚-CL-co-l-LA with tendentially random structure indicated by the average lengths of the caproyl and lactidyl sequences (L_CL = 1.4; L_LA = 2.6). Particularly, addition of excess alcohol into the catalytic system of complex 3 established the first 鈥渋mmortal鈥?copolymerization of 蔚-CL/l-LA, which accelerated the polymerization rates of both monomers and, thus, afforded random copolymers with predictable molecular weights and narrow molecular weight distributions.