title: Stereoselective Alkali-Metal Catalysts for Highly Isotactic Poly(rac-lactide) Synthesis.
abstract: A high degree of chain end control in the isoselective ring-opening polymerization (ROP) of rac-lactide is a challenging research goal. In this work, eight highly active sodium and potassium phenolates as highly isoselective catalysts for the ROP of rac-lactide are reported. The best isoselectivity value of Pm = 0.94 is achieved. The isoselective mechanism is chain-end control through the analysis of the stereoerrors in the microstructure of a final polymer; thus, isotactic multiblock structure polymers are obtained, and the highest melt point can reach 192.5 °C. The donating group in phenolate can clearly accelerate the ROP reaction, potassium complexes are more active than the analogous sodium complexes, and the big spacial hindrance of the ligand can decrease the activity. The high isoselectivities of these complexes mostly result from their sandwich structure constructed by the plane of the crown and the plane of the anthryl group.
authors.affiliation: State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, Lanzhou University , Lanzhou 730000, People's Republic of China.
authors.forename: Yangyang
authors.initials: Y
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, Lanzhou University , Lanzhou 730000, People's Republic of China.
authors.forename: Jiao
authors.initials: J
authors.lastname: Xiong
authors.affiliation: State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, Lanzhou University , Lanzhou 730000, People's Republic of China.
authors.forename: Zhongran
authors.initials: Z
authors.lastname: Dai
authors.affiliation: State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, Lanzhou University , Lanzhou 730000, People's Republic of China.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Pan
authors.affiliation: State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, Lanzhou University , Lanzhou 730000, People's Republic of China.
authors.forename: Ning
authors.initials: N
authors.lastname: Tang
authors.affiliation: State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, Lanzhou University , Lanzhou 730000, People's Republic of China.
authors.forename: Jincai
authors.initials: J
authors.lastname: Wu