New Catalysts for Stereoselective Living Radical Polymerization of Functional α-Olefins

The stereostructure of polymeric chains can greatly influence their physical and chemical properties. Therefore, controlling the stereostructures (tacticity) of polymers is very important in materials chemistry. There have been numerous studies on how to control the tacticity of polymer during a radical polymerization process. However, only a few monomers can be applied to stereospecific living radical polymerization.
A Lewis acid–mediated stereocontrolled atom transfer radical polymerization (ATRP) of various acrylamide monomers was successfully achieved by using the newly designed catalysts. Schiff base-based macrocylclic compounds were synthesized from the condensation of an aryl dialdehyde with achiral and chiral diamines. These macrocyclic Schiff bases and their corresponding reduced macrocyclic amines were used as the ligands for the ATRP. The polymerization was conducted in methanol by using the copper(I)-macrocyclic ligand complex as the catalyst and ethyl 2-bromoisobutyrate as the initiator in the presence of 5 mol % Yb(OTf)3 at room temperature (20℃). Polymers with high isotacticty and narrow polyisodispersity index (PDI) were obtained along with high conversion of the monomers. The resulting poly (N,N-dimethylacrylamide) had an isotacticity as high as 90% and a PDI of 1.05. The resulting poly (N-isopropylacrylamide) had an isotacticity as high as 89% and a PDI of 1.12. It is the first time that the copper-mediated stereocontrolled ATRP of N-isopropylacrylamide was successfully achieved.