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Gallium and indium complexes containing the bis(imino)phenoxide ligand: synthesis, structural characterization and
Swarup Ghosh1, Ravikumar R Gowda, Rajamony Jagan
1Department of Chemistry, Indian Institute of Technology Madras, Chennai-600 036, Tamil Nadu, India.
Dalton Transactions (Cambridge, England : 2003)
|May 16, 2015
Summary
New gallium and indium catalysts enable controlled ring-opening polymerization of lactides. These catalysts produce high molecular weight poly(lactic acid) with tunable tacticity, offering precise control over polymer properties.
Area of Science:
- Organometallic Chemistry
- Polymer Science
- Catalysis
Background:
- Bis(imino)phenolate ligands offer versatile coordination environments for metal centers.
- Ring-opening polymerization (ROP) is a key method for synthesizing polyesters like poly(lactic acid) (PLA).
- Controlling polymer tacticity and molecular weight is crucial for tailoring material properties.
Purpose of the Study:
- To synthesize and characterize novel gallium and indium complexes with bis(imino)phenolate ligands.
- To investigate the catalytic activity of these complexes in the ring-opening polymerization (ROP) of lactides.
- To explore the influence of catalyst structure (neutral vs. ionic) on polymer tacticity and molecular characteristics.
Main Methods:
- Synthesis and full characterization of metal complexes using spectroscopic techniques.
- Single crystal X-ray diffraction for structural elucidation of selected complexes.
- Bulk ring-opening polymerization (ROP) of lactides under melt conditions.
- Polymer characterization including molecular weight (Mn) and molecular weight distribution (MWD) analysis.
- Kinetic and mechanistic studies of the polymerization process.
Main Results:
- Synthesized and characterized novel gallium and indium bis(imino)phenolate complexes.
- Demonstrated high catalytic activity in lactide ROP, yielding high molecular weight polymers.
- Achieved controlled polymerizations with narrow molecular weight distributions (MWDs).
- Neutral complexes produced isotactic-enriched PLA from rac-lactide, while ionic complexes yielded atactic PLA.
- Established linear Mn vs. conversion plots, indicating controlled polymerization.
Conclusions:
- Gallium and indium bis(imino)phenolate complexes are highly effective catalysts for controlled ROP of lactides.
- Catalyst structure dictates the tacticity of the resulting poly(lactic acid).
- These systems offer a promising route for synthesizing well-defined PLA with tunable properties.
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