Functionalized Cyclic Poly(α-Hydroxy Acids) via Controlled Ring-Opening Polymerization of O-Carboxyanhydrides

Area of Science:

• Polymer Chemistry
• Organic Synthesis
• Materials Science

Background:

• Linear poly(α-hydroxy acids) are crucial degradable polymers synthesized via ring-opening polymerization of O-carboxyanhydrides.
• Previous methods for cyclic poly(α-hydroxy acids) synthesis suffered from side reactions, hindering the production of high-molecular-weight, stereoregular polymers.

Purpose of the Study:

• To develop a scalable and controlled method for synthesizing high-molecular-weight, stereoregular cyclic poly(α-hydroxy acids).
• To explore the preparation of cyclic block poly(α-hydroxy acids) using the developed catalytic system.
• To investigate the unique physicochemical properties of the synthesized cyclic polyesters compared to their linear counterparts.

Main Methods:

• Employed a catalytic system comprising a lanthanum complex with a sterically bulky ligand and a manganese silylamide for controlled polymerization.
• Utilized O-carboxyanhydrides as monomers for the ring-opening polymerization.
• Implemented sequential addition of O-carboxyanhydrides to synthesize cyclic block poly(α-hydroxy acids).

Main Results:

• Successfully synthesized high-molecular-weight (>100 kDa) stereoregular functionalized cyclic poly(α-hydroxy acids).
• Achieved facile preparation of cyclic block poly(α-hydroxy acids) through sequential monomer addition.
• Observed distinct physicochemical properties in cyclic polyesters, including elevated phase transition temperature, improved toughness, and reduced viscosity, compared to linear analogs.

Conclusions:

• A novel, scalable method for producing high-molecular-weight stereoregular cyclic polyesters has been established.
• The developed catalytic system enables the synthesis of cyclic block copolymers with tunable properties.
• The unique properties of these cyclic polymers offer potential advantages over traditional linear polymers in various applications.