A series of lithium, sodium and potassium salts containing various iminophenoxide ligand scaffolds have been successfully synthesized in high yields and purity. These complexes were completely characterized with different spectroscopic techniques and single crystal X-ray diffraction studies on a few of them. These compounds were found to be active towards the solvent free ring opening polymerization (ROP) of L-lactide (L-LA) and rac-lactide (rac-LA), yielding polymers with high number average molecular weight (Mn) and controlled molecular weight distribution (MWDs). Poly(lactic acid) (PLA) derived from the ROP of lactides using the Na complexes showed a close proximity between the observed Mn and theoretical molecular weight (Mntheo). In addition, the MWDs were found to be narrow. These complexes were also found to be active for the ROP of lactides in the presence of benzyl alcohol as a co-initiator. The kinetics and mechanistic studies associated with these polymerizations have been performed and reported. © 2014 Elsevier Ltd. All rights reserved.

Debashis Chakraborty

Babu Varghese

Molecular weight distribution

Polymers

Salts

Scaffolds

Single crystals

X ray diffraction

BULK RING OPENING POLYMERIZATION

GROUP 1

IMINO(PHENOXIDE)

Lactides

NUMBER AVERAGE MOLECULAR WEIGHT

Single crystal X-ray diffraction

Structural characterization

Ring opening polymerization

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IIT Madras

European Polymer Journal

Four new copper complexes based on bidentate imino phenoxide ligands were synthesized and characterized by IR, UV–Vis spectroscopy, ESI mass spectrometry, single crystal X-ray diffraction, and electrochemistry. The crystal structures revealed that the copper(II) atoms are surrounded by phenolate oxygen and imine nitrogen atoms of two ligands in a distorted square-planar geometry. The existence of ligand-centered, as well as Cu(II)-centered quasi-reversible and reversible redox reactions are observed in the cyclic voltammetry experiments of all the complexes. All complexes are able to catalyze the ring-opening polymerization of rac-lactide yielding polymers with moderate molecular weights and moderately broad molecular weight distributions. Graphical abstract: [Figure not available: see fulltext.] © 2016, The Author(s).

Fulltext

Monatshefte fur Chemie

Copper(II) complexes with imino phenoxide ligands: synthesis, characterization, and their application as catalysts for the ring-opening polymerization of rac-lactide

In the present study, we have discussed the bulk ring opening polymerization (ROP) of rac-lactide (rac-LA) and ε-caprolactone (ε-CL) using Cd(OAc)2. Cd(OAc)2 appeared to be a good catalyst for the polymerization of rac-LA and ε-CL yielding high molecular weight (Mn) polymers with narrow molecular weight distributions (MWDs). The catalytic activity of the system can be increased markedly upon using catalytic amount of BnOH as external alcoholic initiator. There is a first order dependence of the rate constant with respect to monomer concentrations as understood from the kinetic studies. The rate was found to be faster in the presence of BnOH. The polymerization process was controlled. The polymerization proceeded via the coordination-insertion mechanism without BnOH as well as activated monomer mechanism in the presence of BnOH. In the absence of BnOH, the acetyl group initiated the polymerization as understood from the 1H NMR and MALDI-TOF analysis. The benzyloxy group initiated the polymerization in the presence of BnOH. Moderate activity towards the polymerization of ethylene was observed using MAO as alkyl aluminum activator. The polymerization parameters towards the polymerization of ethylene were widely investigated. [Figure not available: see fulltext.] © 2016, Springer Science+Business Media Dordrecht.

Journal of Polymer Research

Cadmium acetate as a ring opening polymerization catalyst for the polymerization of rac-lactide, ε-caprolactone and as a precatalyst for the polymerization of ethylene

Imino phenoxide complexes of Nb and Ta show precise control towards the solvent free ring-opening polymerization of lactides (LA) and ε-caprolactone (CL). There is a close proximity between the observed number average molecular weight (Mn) and theoretical molecular weight and the molecular weight distributions (MWDs) were found to be narrow. Analysis of low molecular weight oligomers of LA synthesized from these compounds revealed that the ligand is incorporated as one of the end terminal groups in the polymer chain. In addition, these complexes were realized to be precatalysts for the polymerization of ethylene. © 2013 The Royal Society of Chemistry.

Dalton Transactions

Imino phenoxide complexes of niobium and tantalum as catalysts for the polymerization of lactides, ε-caprolactone and ethylene

A complete library of new alkoxides containing group 4 metals and the imino phenol ligand were synthesized in high yields and purity. These compounds showed catalytic activity towards the polymerization of l-lactide (l-LA), rac-lactide (rac-LA), ε-caprolactone (CL), δ-valerolactone (VL), rac-β-butyrolactone (rac-BL), ethylene and propylene. The zirconium catalysts were found to yield better polymerization results in comparison to the titanium and hafnium analogues. The number average molecular weight (M n) values of the polymers are very high for LA and CL with controlled molecular weight distributions (MWDs). Analyses of MALDI-TOF and 1H NMR spectra of low Mn oligomers reveal that the ligand initiates the ring-opening polymerization (ROP). For ethylene and propylene polymerization, we have achieved moderate to good activity using MAO as a co-catalyst. © 2013 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

New Journal of Chemistry

Imino phenoxide complexes of group 4 metals: Synthesis, structural characterization and polymerization studies

A series of aryloxy compounds and benzyloxy derivatives of Zr(IV) were synthesized in good yields and purity, employing the alcoholysis route. They were completely characterized with different spectroscopic techniques and single crystal X-ray diffraction. A high degree of fluxional behavior of these compounds was understood through variable-temperature NMR studies. X-ray diffraction studies prove that these compounds exist as dimers in the solid state. They are potent catalysts for the ring-opening polymerization of ε-caprolactone (CL) and δ-valerolactone (VL) resulting in high polymers with good number average molecular weights (Mn) and molecular weight distributions (MWDs). The degree of control in these polymerizations was found to be superior with the zirconium compounds when compared with the titanium analogues. The rate of polymerization was found to be slower for the zirconium compounds, as realized from kinetic studies. Analysis of the MALDI-TOF and 1H NMR spectra of low molecular weight oligomers of CL synthesized using these compounds reflect that these polymerizations proceed by the activated monomer mechanism. © 2010 Elsevier B.V. All rights reserved.

Journal of Organometallic Chemistry

Aryloxy and benzyloxy compounds of zirconium: Synthesis, structural characterization and studies on solvent-free ring-opening polymerization of ε-caprolactone and δ-valerolactone

Dinuclear salen compounds of zirconium and hafnium are efficient initiators for the solvent-free ring-opening polymerization of cyclic ester monomers and lactides. There is a correlation between the theoretical and experimental number-average molecular weights (Mn's) in these polymerizations. Polymerization of β-butyrolactone gives poly(3-hydroxybutyrate) with a good Mn and molecular weight distribution. © 2011 American Chemical Society.

Inorganic Chemistry

Salen complexes of zirconium and hafnium: Synthesis, structural characterization, controlled hydrolysis, and solvent-free ring-opening polymerization of cyclic esters and lactides

New phosphoroamidate compounds with 1,1′-Bi-2-napthol (binol) ligand were synthesized from the corresponding phosphorochloridate intermediates and benzyl amine or benzyl amine derivatives. They were completely characterized using different spectroscopic methods and single crystal X-ray diffraction studies. These compounds effectively catalyze the ring-opening polymerization of -caprolactone (CL) and l-lactide (LA). This methodology of polymer synthesis is green and environmental benign since phosphorus is a natural constituent of human anatomy and these polymers being completely biodegradable. © 2011 Elsevier B.V. All rights reserved.

Inorganica Chimica Acta

Phosphoroamidate compounds of 1,1′-Bi-2-napthol: Synthesis, structural characterization and solvent-free ring-opening polymerization of -caprolactone and l-lactide

Group 1 salts of the imino(phenoxide) scaffold: Synthesis, structural characterization and studies as catalysts towards the bulk ring opening polymerization of lactides

Journal	Data powered by TypesetEuropean Polymer Journal
Publisher	Data powered by TypesetElsevier Ltd
ISSN	00143057
Open Access	No