Dual Catalysis for Selective Ring-Opening Polymerization of Lactones: Evolution toward Simplicity

Area of Science:

• Polymer Chemistry
• Catalysis
• Organic Synthesis

Background:

• Ring-opening polymerization (ROP) traditionally relies on complex single-site catalysts.
• Cooperative catalysis using Lewis acids and organocatalysts presents a simpler, effective alternative for ROP.

Purpose of the Study:

• To investigate the cooperative effect of N-heterocyclic carbenes (like DBU and DMAP) with Lewis acids for ROP.
• To explore monomer selectivity and control over copolymer composition using this catalytic system.

Main Methods:

• Utilized a combination of N-heterocyclic carbenes (DBU, DMAP) and various Lewis acids (MgX2, YCl3, AlCl3).
• Conducted ROP of pentadecalactone and other cyclic (di)esters.
• Analyzed catalyst activity and selectivity based on Lewis acid and organobase choice.

Main Results:

• Achieved rapid and efficient ROP of pentadecalactone using the cooperative catalytic system.
• Established a clear activity trend for Lewis acids: MgX2 ≫ YCl3 ≫ AlCl3 and MgI2 > MgBr2 > MgCl2.
• Demonstrated monomer-selective ROP and control over copolymer composition by judicious Lewis acid selection.

Conclusions:

• Cooperative catalysis with simple Lewis acids and organocatalysts is a powerful strategy for ROP.
• This method allows for the synthesis of complex polymers with tunable properties from accessible precursors.
• The Lewis acid choice dictates monomer selectivity, enabling precise control over polymer architecture.