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 (Mw/Mn < 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.
Highlights
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
We extend our previously reported photoredox ring-opening polymerization (ROP) protocol to accomplish stereoselective ROP of OCAs, and we present a new approach to the synthesis of stereoblock polyesters, as well as the formation of gradient copolymers (Fig. 1c)
We discovered that within 4 h of irradiation at –15 ° C, photoredox ROP mediated by (NNO-1)ZnEt ([L-1]/[D-1]/ [Zn]/[Ni]/[benzyl alcohol (BnOH)]/[Ir-1] = 150/150/1/1/1/0.1) resulted in a product with a Mn of 45.7 kDa, which was close to the expected MW (44.5 kDa), and a narrow Đ (1.06) (Table 2, entry 1)
Summary
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. 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. Polyesters with various microstructures have been synthesized by means of stereoselective ring-opening polymerization (ROP) of racemic lactide and β-lactones[17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33], including the use of newly developed switchable catalysts[34,35,36]. We extend our previously reported photoredox ROP protocol to accomplish stereoselective ROP of OCAs, and we present a new approach to the synthesis of stereoblock polyesters, as well as the formation of gradient copolymers (Fig. 1c)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
