A Novel Dimetallic {(salen) Al} Complexes: Synthesis Characterization And Stereoselective Ring-opening Polymerization Of Arc-lactides

Ploylactide is a widely researched biodegradable material, whichhas a wide range of uses such as green plastics for textiles andpackaging films, scaffolds for tissue engineering, drug controlleddelivery systems. Usually, the method to prepare PLA is ring-openingpolymerization (ROP) of lactide. Lactide has three differentstereoisomers: D-lactide, L-lactide and meso-lactide, so PLA hadmany kinds of stereoisomers, such as isotactic-PLA, heterotactic-PLAand stereoblock-PLA. In these unequal stereoisomers, the equivalentPLLA and PDLA may form a crystalline stereocomplex, whichmelting temperature is as high as230℃. So it is interesting toproduce the stereocomplex directly from the rac-lactide monomer,(salen)-Al complexes are excellent catalysts in stereoselective ROP ofrac-LA which had been proved by many researches. We developed avariable synthetic method toward dinuclear salen system, andsynthesized a novel dinuclear Schiff base ligand and complex. Inapplication of ROP rac-LA by using the complex as a catalystindicated the complex has distinct activity and stereoselective, andthe electronic and structural properties of different substituents onthe ligand and steric structure of the ligand play an important role inthe catalytic propertie which were also discussed.