請用此 Handle URI 來引用此文件: http://hdl.handle.net/11455/34014
標題: Ring-Opening Polymerization of Lactides Initiated by Magnesium and Zinc Complexes Based on NNO-Tridentate Ketiminate Ligands: Activity and Stereoselectivity Studies
作者: Huang, Y.
林助傑
Hung, W.C.
Liao, M.Y.
Tsai, T.E.
Peng, Y.L.
Lin, C.C.
關鍵字: catalysts
ketiminate
living polymerization
polyesters
rac-lactide
rac-lactide
metal-complexes
cyclic esters
racemic lactide
poly(lactic acid)
efficient initiators
epsilon-caprolactone
beta-diketone
catalysts
alkoxides
期刊/報告no:: Journal of Polymer Science Part a-Polymer Chemistry, Volume 47, Issue 9, Page(s) 2318-2329.
摘要: Four metal benzylalkoxides, [L(2)M(2)(mu-OBn)(2)] (M = Mg or Zn), based on NNO-tridentate ketiminate ligands are synthesized and characterized. X-ray crystal structural studies of [(L(1))(2)Mg(2)(mu-OBn)(2)] (1a) and [(L(1))(2)Zn(2)(mu-OBn)(2)] (1b) (L(1)-H = (Z)-4-((2-(dimethylamino)ethylamino)(phenyl)methylene)-3-methyl-1-phenyl-pyrazol-5-one) reveal that both complexes 1a and 1b are dinuclear species whereas the geometry around the metal center is penta-coordinated bridging through the benzylalkoxy oxygen atoms in the solid structure. The activities and stereoselectivities of these four complexes toward the ring-opening polymerization Of L-lactide and rac-lactide are investigated. Polymerization Of L-lactide initiated by these four metal benzyloxides proceeds rapidly with good molecular weight control and yields polymer with a very narrow molecular weight distribution. The kinetic studies for the polymerization of L-lactide with compound 1a show first order in both compound 1a and lactide concentrations with the polymerization rate constant, k, of 6.94 M/min. Besides, experimental results demonstrate that among these metal benzylalkoxides, complex 1a exhibits the highest stereoselectivity with a Pr up to 87% and complex 1b possesses the highest activity indicating that the terminal group of NNO-tridentate ketimine ligands exerts a significant influence on both the reactivity and stereoselectivity of these complexes. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2318-2329, 2009
URI: http://hdl.handle.net/11455/34014
ISSN: 0887-624X
文章連結: http://dx.doi.org/10.1002/pola.23314
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