Divergent [{ONNN}Mg-Cl] complexes in highly active and living lactide polymerization

Area of Science:

• Coordination Chemistry
• Polymer Science
• Materials Science

Background:

• Tetradentate-monoanionic {ONNN}-type ligands are crucial in coordination chemistry.
• Catalysis of ring-opening polymerization (ROP) is key for polymer synthesis.

Purpose of the Study:

• To synthesize and characterize novel chloro-magnesium complexes with {ONNN}-type ligands.
• To investigate the catalytic activity of these complexes in lactide polymerization.
• To explore the synthesis of well-defined polylactic acid (PLA) copolymers.

Main Methods:

• Synthesis of mononuclear and dinuclear chloro-magnesium complexes.
• Ring-opening polymerization (ROP) of lactide.
• Characterization of resulting polymers using techniques like GPC, NMR, thermal analysis, and crystallography.

Main Results:

• The complexes exhibited high activity and living characteristics in lactide ROP.
• Synthesis of stereo-diblock and stereo-n-block copolymers (n=tri, tetra) with molecular weights exceeding 200 kDa.
• High molecular weight PLA copolymers crystallized in a stereocomplex phase.
• Degradation temperature of the PLA copolymers reached up to 354 °C.

Conclusions:

• Chloro-magnesium complexes with {ONNN}-type ligands are effective catalysts for controlled PLA synthesis.
• The catalysts enable the production of high molecular weight, well-defined PLA copolymers with excellent thermal properties.
• This work advances the field of controlled polymerization and high-performance biodegradable polymers.