Aluminium complexes bearing N, O-aminophenol ligands as efficient catalysts for the ring opening polymerization of lactide. (September 2015)

• Record Type: Journal Article
• Authors: Roymuhury, Sagnik K.; Chakraborty, Debashis; Ramkumar, Venkatachalam
• Is Part Of: European polymer journal. Volume 70(2015)
• Page Start: 203
• Page End: 214
• Publication Date: 2015-09
• Subjects: Aluminium -- Aminophenol -- Single crystal X-ray structure -- Ring opening polymerization -- DFT; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; Polymerization; Polymers; Periodicals; Electronic journals; 547.705
• DOI: 10.1016/j.eurpolymj.2015.07.025
• Languages: English
• ISSNs: 0014-3057

Abstract

Graphical abstract: Ring opening polymerization of lactide using aluminium complexes bearing aminophenol ligands is described. Highlights: High yield route to dimethyl aluminium complexes containing aminophenol ligand. Polymerization of lactide is well controlled. PLA from rac -LA is heterotactically enriched. Low molecular weight oligomers of PLA thoroughly characterized. Abstract: Three new dimethyl aluminium complexes 1 –3 containing aminophenol ligands (LAlMe2, where L1 = diethylaminophenoxide, L2 = diisopropylaminophenoxide and L3 = piperidinophenoxide) were synthesized and characterized by different spectroscopic techniques and elemental analysis. The solid state structure of 1 was determined by single crystal X-ray diffraction studies. The data revealed that 1 possesses as a distorted tetrahedral geometry around the aluminium centre. The catalytic activities of these complexes towards the ring opening polymerization (ROP) of rac -lactide ( rac -LA) and L -lactide ( L -LA) were examined and good efficiency with controlled number average molecular weight ( M n ) and narrow molecular weight distributions (MWDs) were achieved. Homonuclear decoupled 1 H NMR spectrum confirms the heterotactic enrichment in the PLA obtained from rac -LA. The MALDI-TOF mass and 1 H NMR spectra of low molecular weight oligomers revealed that the aminophenoxide ligand initiates the ROP. The geometries of all the complexes were optimized at B3LYP/LANL2DZ level and DFT calculations were carried out in order to establish the relation between the reactivity and the HOMO–LUMO energy gap.