Cu(OAc)2 was assessed to be a good catalyst for the bulk ring opening polymerization of lactides. These polymerizations are highly controlled leading to the formation of polymer with expected number average molecular weights and narrow molecular weight distribution. This method may be used to synthesize polymers with different end terminal groups. The over all process is green, since these polymers being biodegradable and the system is independent of solvents. © 2011 Elsevier B.V. All rights reserved.

Debashis Chakraborty

ACTIVATED MONOMER MECHANISM

BULK RING OPENING POLYMERIZATION

COORDINATION-INSERTION MECHANISM

COPPER ACETATES

END TERMINALS

Lactides

NARROW MOLECULAR WEIGHT DISTRIBUTIONS

NUMBER AVERAGE MOLECULAR WEIGHT

Ring opening

Biodegradable polymers

Molecular weight distribution

Ring opening polymerization

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Molecular Catalysis A: Chemical

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

Chlorides of group 4 metals containing the bis(imino)phenoxide ligand scaffold were synthesized from a direct reaction between the respective ligand and metal chlorides MCl4 (M=Ti, Zr and Hf). These complexes were thoroughly characterized using various spectroscopic methods and single crystal X-ray diffraction studies. They are potent catalysts for the polymerization of rac-lactide (rac-LA), L-lactide (L–LA), ϵ-caprolactone (ϵ-CL), epoxides such as, rac-cyclohexene oxide (rac-CHO), rac-propylene oxide (rac-PO), rac-styrene oxide (rac-SO) and ethylene, resulting in polymers with high number average molecular weights (Mn) and narrow molecular weight distributions (MWDs). The kinetic and mechanistic studies associated with the polymerization of lactide, ϵ-CL and CHO has been investigated in details. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

ChemistrySelect

Zwitterionic Complexes of Group 4 Metal Chlorides Containing a Bis(imino)phenoxide Scaffold: Synthesis, Characterization and Polymerization Studies

A plethora of magnesium compounds containing imino(phenoxide) (1-4) and bis(imino)phenoxide (5-10) ligand backbone have been synthesized via the reaction of diethyl magnesium with two equivalent of the corresponding ligand. These compounds were completely characterized by different spectroscopic techniques and elemental analyses. The monomeric nature of the magnesium complexes 3, 5, 6, 9, and 10 were further confirmed by single crystal X-ray diffraction studies. The magnesium centers posses distorted trigonal bipyramidal geometry. The controlled hydrolysis compound Mg7O8 (C22H28NO2)6 (11) was adequately characterized using 1H, 13C NMR, ESI-MS, and the biscubane structure was further confirmed by single crystal X-ray diffraction studies. The Mg7O8 core is deeply embedded with the ligand periphery. These compounds (1-10) were found to be active towards the bulk ring opening polymerization (ROP) of lactides, yielding polymers with high number average molecular weight (Mn) and controlled molecular weight distributions (MWDs). In addition, these compounds have been shown to be highly active toward the copolymerization of carbon dioxide with cyclohexene oxide and styrene oxide. © 2015 Wiley Periodicals, Inc. J. Polym. Sci.

Journal of Polymer Science, Part A: Polymer Chemistry

Imino(phenoxide) compounds of magnesium: Synthesis, structural characterization, and polymerization studies

Co(II) and Mn(II) salts were assessed to be good catalysts for the bulk ring-opening polymerization of cyclic esters. These polymerizations are reasonably controlled leading to the formation of polymer with good number average molecular weights (M n) and narrow molecular weight distributions. The polymerizations were studied in the presence and absence of benzyl alcohol and the polymerization tendency was found to increase in the presence of benzyl alcohol. The polymerization proceeds through the activated monomer mechanism, resulting in the formation of polymers containing the initiator as one of the end terminal groups. All the polymerizations show first-order kinetics with respect to monomer concentration. Ease of handling and low cost of Co(II) and Mn(II) salts make the catalytic process economically attractive. © 2014 Springer-Verlag Berlin Heidelberg.

Polymer Bulletin

Co(II) and Mn(II) catalyzed bulk ring-opening polymerization of cyclic esters

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

Bis(imino)phenoxide complexes of zirconium possess spectacular reactivity towards the solvent-free polymerization of cyclic ester monomers and lactides. Polymerization of lactide is living and the resulting product has exceptionally high number average molecular weights (Mn). Polymerization of β-butyrolactone gives syndiotactic poly(3-hydroxybutyrate) with good M n and molecular weight distribution (MWD). © The Royal Society of Chemistry 2010.

Dalton Transactions

Bis(imino)phenoxide complexes of zirconium: Synthesis, structural characterization and solvent-free ring-opening polymerization of cyclic esters and lactides

A large variety of aryloxy compounds and benzyloxy derivatives of Hf(IV) were synthesized from Hf(O-tBu)4 using the alcoholysis route. These compounds were completely characterized using various spectroscopic and analytical methods along with single crystal X-ray diffraction studies. Multinuclear NMR studies prove high degree of fluxional behavior of these compounds in solution. They adopt a dimeric structure in the solid-state as seen from X-ray diffraction studies on a few of them. These compounds are powerful catalysts for the ring-opening polymerization of ε-caprolactone (CL) and δ-valerolactone (VL) resulting in high number average molecular weight (Mn) polymers and controlled molecular weight distributions (MWDs). Significant control in the polymerization was achieved with these compounds as initiators in comparison to their titanium and zirconium analogues. Kinetic studies reveal that the rates of such polymerizations are in general slower than the corresponding titanium and zirconium derivatives. 1H NMR and MALDI-TOF studies of low molecular weight oligomers suggest that these polymerizations proceed by the activated monomer mechanism. © 2010 Elsevier Ltd.

Polymer

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

Zn(OAc)2·2H2O is found to be an effective bulk polymerization catalyst for the ring-opening polymerization of rac-lactide, l-lactide, ε-caprolactone and δ-valerolactone. The propensity of polymerizations can be enhanced by performing them in the presence of appropriate amounts of different alcohols. The major initiation pathway in the polymerization is found to proceed via the activated monomer mechanism and depending on the nature of the alcohol used, polymers with different end groups can be synthesized. These polymerization system constitutes an economical process, employing readily available inorganics such as Zn(OAc) 2·2H2O as catalyst and do not necessitate solvents. The overall system is green and eco friendly. © 2010 Elsevier B.V.

Journal	Journal of Molecular Catalysis A: Chemical
ISSN	13811169
Open Access	No