S-Carboxyanhydrides: Ultrafast and Selective Ring-Opening Polymerizations Towards Well-defined Functionalized...

Area of Science:

• Polymer Chemistry
• Organic Synthesis
• Materials Science

Background:

• Aliphatic polythioesters offer desirable properties like metal coordination, high refractive indices, and biodegradability.
• Ring-opening polymerization (ROP) of cyclic monomers is a key method for polythioester synthesis.
• Current ROP methods using thiolactones face limitations in monomer diversity and side reactions like transthioesterification.

Purpose of the Study:

• To introduce a novel class of highly reactive S-carboxyanhydride (SCA) monomers for ultrafast and selective ROP.
• To overcome the limitations of existing thiolactone-based ROP methods.
• To enable the synthesis of precisely controlled and functionalized polythioesters.

Main Methods:

• Utilized S-carboxyanhydride (SCA) monomers derived from amino acids for ROP.
• Employed bis(triphenylphosphine)-iminium (PPNOBz) as initiator and benzoic acid as a chain transfer agent.
• Conducted polymerizations in open vessels at room temperature.
• Performed computational studies to elucidate reaction mechanisms.

Main Results:

• Achieved complete monomer conversion within 1-2 minutes at room temperature.
• Synthesized polythioesters with predictable molecular weights, low dispersities, and retained stereoregularity.
• Demonstrated the incorporation of functional groups via functionalized SCAs, allowing fine-tuning of polymer properties.
• Confirmed chemical recyclability of the resulting polythioesters.

Conclusions:

• SCA monomers offer significantly higher reactivity and selectivity for ROP compared to thiolactones.
• This new ROP approach enables rapid, controlled synthesis of diverse and functional aliphatic polythioesters.
• The findings provide mechanistic insights into the high efficiency and selectivity of SCA polymerization, paving the way for advanced polymer materials.