Multimetallic lithium and chromium complexes of amine-bis(phenolate) ligands as polymerization catalysts

Dean, Rebecca (2012) Multimetallic lithium and chromium complexes of amine-bis(phenolate) ligands as polymerization catalysts. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The synthesis of biodegradable and/or bioassimilable plastics has been growing in importance throughout the past decade. The steadily decreasing supply of fossil fuels, coupled with increased environmental awareness, has spurred an interest in alternative, renewable feedstocks for use in a variety of applications. The plastics industry is no exception. Therefore, an investigation of lithium and chromium complexes was undertaken for the catalytic synthesis of polyesters and polycarbonates from renewable feedstocks. -- The ligands used in this thesis were tetradentate tripodal amine-bis(phenolates), where the substituents on the phenolate groups and pendant arm could be varied. The synthesis and characterization of mono- and dimeric lithium complexes was performed. The lithium complexes were then used to synthesize a series of chromium(III) complexes by two methods. Salt-metathesis and protonolysis/oxidation routes were used to produce mono- and dimeric, paramagnetic Cr(III) complexes. The isolated complexes were characterized by NMR (where appropriate), IR, UV-Vis spectroscopy, mass spectrometry, magnetometry, cyclic voltammetry and elemental analysis. In addition, an attempt was made to synthesize Cr amide and alkyl complexes of these ligands. -- The polymerization of rac-lactide to yield polylactide, was studied with lithium salts of amine-bis(phenolate) ligands. Polymerization studies found that ring-opening polymerization of rac-lactide was possible in the presence or absence of an alcohol as a co-initiator. As well, the copolymerization of propylene oxide and cyclohexene oxide with CO₂ to yield polycarbonates was investigated with chromium(III) amine- bis(phenolate) complexes. Polymers synthesized were shown to have high selectivity, great CO₂ incorporation and low polydispersities. Polymer analysis involved ¹H and ¹³C NMR, mass spectrometry, GPC, DSC and TGA.

Item Type: Thesis (Doctoral (PhD))
URI: http://research.library.mun.ca/id/eprint/10385
Item ID: 10385
Additional Information: Includes bibliographical references.
Department(s): Science, Faculty of > Chemistry
Date: 2012
Date Type: Submission
Library of Congress Subject Heading: Biodegradable plastics--Synthesis; Polymerization; Metal complexes; Ligands--Synthesis; Catalysts.

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