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Selective Transesterification to Control Copolymer Microstructure in the Ring-Opening Copolymerization of Lactide and
Bette Beament1, Daniel Britton1, Thomas Malcomson2
1Department of Chemistry, Lancaster University, Lancaster LA1 4YB, United Kingdom.
Inorganic Chemistry
|December 21, 2023
Summary
Novel lanthanum amido complexes catalyze ring-opening polymerization of lactide and caprolactone. Catalyst structure and solvent control copolymer microstructure, enabling tailored polymer properties.
Area of Science:
- Coordination Chemistry
- Polymer Science
- Catalysis
Background:
- Lanthanum complexes are increasingly studied for catalytic applications.
- Salan ligands offer tunable steric and electronic properties for metal complex design.
- Ring-opening polymerization (ROP) is a key method for synthesizing biodegradable polyesters.
Purpose of the Study:
- To synthesize and characterize novel lanthanum amido complexes with salan-based ligands.
- To investigate the catalytic activity of these complexes in the ROP of lactide (LA) and ε-caprolactone (ε-CL).
- To explore the influence of catalyst structure and reaction conditions on copolymerization and microstructure.
Main Methods:
- Synthesis and full characterization of lanthanum amido complexes.
- Catalytic investigation of homopolymerization and copolymerization of LA and ε-CL.
- Analysis of reaction products using gel permeation chromatography-size-exclusion chromatography (GPC-SEC).
Main Results:
- Novel lanthanum amido complexes were successfully synthesized and characterized.
- Catalysts demonstrated high activity in LA polymerization and LA/ε-CL copolymerization.
- Solvent and ligand substituents (pyridyl groups) significantly impacted catalyst reactivity and selectivity.
- Copolymer microstructure (blocky to alternating) was tunable by catalyst design and solvent choice.
- Transesterification mechanisms (TI or TII) were found to be dependent on catalyst and solvent.
Conclusions:
- Lanthanum amido complexes are effective catalysts for LA and ε-CL polymerization.
- Catalyst structure and reaction solvent are critical for controlling copolymer composition and microstructure.
- This work provides a pathway for designing catalysts to achieve specific polyester properties.
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