Stereoselective photoredox ring-opening polymerization of O-carboxyanhydrides.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 29674720.
- Also identified by DOI 10.1038/s41467-018-03879-5 and PMC identifier 5908805.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Biodegradable polyesters with various tacticities have been synthesized by means of stereoselective ring-opening polymerization of racemic lactide and β-lactones but with limited side-chain groups. However, stereoselective synthesis of functional polyesters remains challenging from O-carboxyanhydrides that have abundant pendant side-chain functional groups. Herein we report a powerful strategy to synthesize stereoblock polyesters by stereoselective ring-opening polymerization of racemic O-carboxyanhydrides with the use of photoredox Ni/Ir catalysts and a selected Zn complex with an achiral ligand. The obtained stereoblock copolymers are highly isotactic with high molecular weights ( > 70 kDa) and narrow molecular weight distributions (M<sub>w</sub>/M<sub>n</sub> < 1.1), and they display distinct melting temperatures that are similar to their stereocomplex counterparts. Furthermore, in one-pot photoredox copolymerization of two different O-carboxyanhydrides, the use of such Zn complex mediates kinetic resolution of the comonomers during enchainment and shows a chirality preference that allows for the synthesis of gradient copolymers.