3 research outputs found
Heterolepic ÎČâKetoiminate Zinc Phenoxide Complexes as Efficient Catalysts for the Ring Opening Polymerization of Lactide
Zinc phenoxide complexes L1ZnOAr 1â4 (L1=Me2NC2H4NC(Me)CHC(Me)O) and L2ZnOAr 5â8 (L2=Me2NC3H6NC(Me)CHC(Me)O) with donor-functionalized ÎČ-ketoiminate ligands (L1/2) and OAr substituents (Ar=Ph 1, 5; 2,6-Me2-C6H3 2, 6; 3,5-Me2-C6H3 3, 7; 4-Bu-C6H4 4, 8) with tuneable electronic and steric properties were synthesized and characterized. 1â8 adopt binuclear structures in the solid state except for 5, while they are monomeric in CDCl3 solution. 1â8 are active catalysts for the ring opening polymerization (ROP) of lactide (LA) in CH2Cl2 at ambient temperature and the catalytic activity is controlled by the electronic and steric properties of the OAr substituent, yielding polymers with high average molecular weight (Mn) and moderately controlled molecular weight distribution (MWDs). 1 and 5 showed a living polymerization character and kinetic studies on the ROP of LâLA with 1 and 5 proved first order dependencies on the monomer concentration. Homonuclear decoupled 1H-NMR analyses of polylactic acid (PLA) formed with rac-LA proved isotactic enrichment of the PLA microstructure. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA