Efficient zinc initiators supported by NNO‐tridentate ketiminate ligands for cyclic esters polymerization

Abstract

A series of zinc benzylalkoxide complexes, [L n Zn(l-OBn)] 2 (L ¼ L 1 H-L 5 H), supported by NNO-tridentate ketiminate ligands with various electron withdrawing-donating subsituents have been synthesized and characterized. X-ray crystal structural studies revealed that complexes 2b and 4b are dinuclear bridging through the benzylalkoxy oxygen atoms with penta-coordinated metal centers. All the metal complexes have acted as efficient initiators for the ring-opening polymerization of L-lactide (within 12 min, 0 C). Remarkably, a molecular weight of PLLA up to 580,000 can be achieved using [(L 5 Zn(l-OBn)] 2 (5b) as an initiator.The kinetic studies for the polymerization of L-lactide with complex 3b at À10 C corresponded to first-order reactions in the monomer. The ring-opening polymerization (ROP) of e-caprolactone, e-decalactone, b-butyrolactone and their copolymer with complex 3b was investigated.

Benzotriazole Phenoxide Hafnium Complexes as Efficient Catalysts for the Ring‐Opening Polymerization of Lactide: Synthesis, Characterization, and Kinetics of Polymerization Catalysis

“…On the basis of these kinetic results, the overall rate equation is –d[ L ‐LA]/d t = k p [ 4 ] 1 [ L ‐LA] 1 , that is, the ROP of L ‐LA is first order in both complex 4 and monomer concentrations. The overall rate law of the polymerization initiated by BTP‐ligated Hf complex 4 agrees with the previously reported metal alkoxide catalytic systems proposed to be first order in both monomer and initiator 3c,16…”

Synthesis of mid-chain functional macrophotoinitiators of poly(D,L-lactide) homopolymer and tetrablock poly(D,L-lactide)-poly(ε-caprolactone) copolymer by ring-opening polymerization

“…[1][2][3] The ring-opening polymerization (ROP) of cyclic esters initiated by metal alkoxides/hydroxyl functionalized initiator systems, via coordination-insertion mechanism, is the most efficient approach to produce polymers based on PCL and PLA with controlled molecular weights and lower molecular weight distributions. In the synthesis of PLA-and PCL-based polymers, the most suitable and practical method is ROP initiated technique by metal alkoxides, such as aluminum, [4,5] zinc, [6][7][8] and tin alkoxides. [9,10] Among them, tin octoate, Sn(Oct) 2 , is certainly the catalyst most widely used [9,11,12] to synthesize such designed polymers via coordination-insertion mechanism.…”

Ring-opening polymerization of ε-caprolactone catalysed by (pyridyl)benzoazole Zn(II) and Cu(II) complexes

“…The first generation of active metal-based catalysts were derived from tin(II) bis (2-ethylhexanoate), and aluminium(III) isopropoxides (AlO i Pr 3 ) [7]. However, the toxicity associated with most tin and aluminium compounds remains a major challenge in their industrial applications, especially in biomedical fields [7][8][9]. More recently, Zn(II) and Cu(II) complexes have received considerable attention as catalysts in ROP of cyclic esters due to their low toxicity, affordability and ease of synthesis [10].…”