8-Quinolinolato gallium complexes: iso-selective initiators for rac-lactide polymerization

Area of Science:

• Organometallic Chemistry
• Polymer Science
• Catalysis

Background:

• Aluminum complexes are known initiators for lactide polymerization.
• Understanding alternative metal complexes can lead to improved catalytic systems.
• 8-quinolinolato ligands offer unique coordination properties.

Purpose of the Study:

• To synthesize and characterize novel 8-quinolinolato gallium complexes.
• To evaluate their efficacy as initiators for the ring-opening polymerization (ROP) of rac-lactide.
• To compare their catalytic performance against analogous aluminum complexes.

Main Methods:

• Synthesis and full characterization of a series of 8-quinolinolato gallium complexes.
• Investigation of their activity in the ring-opening polymerization of rac-lactide.
• Analysis of polymerization control via molecular weight evolution, polydispersity, and iso-selectivity (Pi).

Main Results:

• The synthesized gallium complexes are active initiators for rac-lactide ROP.
• Excellent polymerization control was achieved, evidenced by linear molecular weight growth, narrow polydispersity, and predicted molecular weights.
• Some complexes exhibited high iso-selectivity (Pi = 0.70) and polymerization rates approximately three times higher than analogous aluminum compounds.

Conclusions:

• 8-quinolinolato gallium complexes represent a promising class of initiators for controlled lactide polymerization.
• These gallium-based systems outperform their aluminum counterparts in terms of polymerization rate while maintaining high control and selectivity.
• The findings open avenues for developing more efficient catalysts for biodegradable polymer synthesis.