The use of Cu and Zn salicylaldimine complexes as catalyst precursors in ring opening polymerization of lactides: ligand effects on polymer characteristics

Abstract

A range of monomeric tetra-coordinate copper (II) and zinc (II) complexes based on N,O-bidentate salicylaldimine Schiff base ligands has been synthesized and characterized using various spectroscopic techniques. These complexes were then evaluated as initiators in ring-opening polymerization of lactides at both 70• C and 110• C. The effect of structural changes in the complexes on the ability of these compounds to initiate lactide polymerization as well as the impact on the chemical and physical characteristics of the polymers obtained indicate that the coordination geometry of the metal complex, M-O bond length and substituents on the Schiff base ligand all play a role in the catalyst activity. Electronic factors were dominant in the case of the copper complexes while steric factors prevailed in the case of Zn initiators. Both the Zn and Cu complexes exhibit characteristics of living ring opening polymerization.

Polymerization of lactide and synthesis of block copolymer catalyzed by copper (II) Schiff base complex

“…benzyl alcohol in polymerization reactions, the 154 molecular weights became half or one fourth, respectively. 155 Our polymerization results are much superior to those reported 156 for copper complexes with elaborate ligands [15][16][17][18]. Literature 157 report for the polymerization of L-lactide using three different 158 copper phenoxy-ketimine complexes at 160 o C found to be 159 M n = 2200 4500 and 6500 g/mol, respectively [16] suggests our 160 results are superior in terms of M n ( Table 1).…”

“…Copper is a biocompatible metal 21 supporting the survival of life and to the best of our knowledge 22 there have been few reports on copper initiators having nitrogen- 23 containing polydentate ligands and their application in ROP of 24 lactide. These include copper complexes derived from pyrazole 25 [15], phenoxy-ketimine [16], salicylaldimine [17], and diketimi-26 nate [18] which are active toward polymerization of lactides and 27 produce polymer with moderate number average molecular 28 weights and narrow molecular weight distribution. Nowadays, 29 all the commercial PLAs are synthesized using FDA-approved 30 stannous octanoate as catalyst.…”

Synthesis and Application of Bimetallic Zinc(II) Phenoxy-Imine Complexes as Initiators for Production of Lactide Polymers

“…[10][11][12][13] An ethanolic solution (15 mL) of 3,5-diiodine-2-hydroxybenzaldehyde (1.244 g, 2 mmol) was added dropwise to an ethanolic solution (15 mL) of 2,3,5,6-tetramethylphenylenediamine (0.164 g, 1 mmol). The reaction mixture was refluxed for 3 h and then stirred overnight at room temperature.…”

Synthesis, characterization and catalytic activity of zinc complex for ring‐opening polymerization of lactide

“…To the best of our knowledge, there have been few reports on zinc initiators having nitrogen‐containing polydentate ligands and their application in the ROP of lactide. Different transition metal complexes supported by pyrazole, phenoxy‐ketimine, salicylaldimine and diketiminate are active towards the ROP of lactide. Nowadays, all the commercial PLAs are synthesized by using the US Food and Drug Administration approved stannous octanoate as catalyst.…”