Synthesis of Aluminum-Schiff Base Catalyst and Their Stereoselective Polymerization of Lactides

Abstract

a series of asymmetric schiff-base ligands and their aluminum al (iii) complexes that contained different steric substituent were designed and synthesized. the structures of ligands and their complexes were characterized. one crystal of schiff-base aluminum complex was obtained. x-ray diffraction analyses showed that the central aluminum atoms of the complex adopt twisted four pyramid geometry. they were chiral but racemic complexes with two enantiomers in solid state. their catalytic properties in the solution polymerization of racemic lactides (rac-la) in the presence of 2-propanol were investigated in detail. all of the complexes had poor stereoselectivity for ring-opening polymerization (rop) of rac-la (p-m about 0. 55), the polymerization rate of asymmetric complex was much faster than symmetric complex in rop of rac-la. the results evaluate that the substituent of ligands has great influence on the catalytic properties of the complex.