Zinc complexes containing asymmetrical N,N,O-tridentate ligands and their application in lactide polymerization.
A series of zinc complexes based on asymmetrical N,N,O-tridentate ligands were prepared via binaphthyl diamine derivatives. These complexes were characterized and employed as catalysts in lactide polymerization. The X-ray diffraction analyses revealed that molecular structures of 1b and 2b were mononuclear complexes with zinc atoms in distorted octahedral geometries. Upon co-catalysis with isopropanol, complex 2a showed the highest activity among these zinc complexes for the ring-opening polymerization of L-lactide, and complex 3a exhibited the highest stereoselectivity for the ring-opening polymerization of rac-lactide affording substantially isotactic polylactide (PLA) with a P(m) of 0.62. The polymerization kinetics using 2a as a catalyst was studied in detail. The kinetics of the polymerization results revealed that the rates of polymerization were first-order both in the monomer and the catalyst, and there was a linear relationship between the L-LA conversion and the number-average molecular weight of PLA with a narrow molecular distribution (1.07-1.17). The activation energy (31.49 kJ mol(-1)) was deduced according to the Arrhenius equation.
Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022, China. xpang@ciac.ac.cn.
Bo
B
Gao
Ranlong
R
Duan
Xuan
X
Pang
Xiang
X
Li
Zhi
Z
Qu
Huili
H
Shao
Xianhong
X
Wang
Xuesi
X
Chen
D002384:Catalysis; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004146:Dioxanes / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D008968:Molecular Conformation; D011091:Polyesters / Q000737:chemistry; D058105:Polymerization; D015032:Zinc / Q000737:chemistry*
D056831:Coordination Complexes; D004146:Dioxanes; D008024:Ligands; D011091:Polyesters; C033616:poly(lactide); C091880:dilactide; D015032:Zinc