Abstract
Aluminum complexes coordinated by bipyridine-phenolate (BpyPh) ligands of 2-([2,2′-bipyridin]-6-yl)-4,6-di-tert-butylphenol (BpyPh 2,4-tBu -H), 2-([2,2′-bipyridin]-6-yl)-4-(tert-butyl)phenol (BpyPh 4-tBu -H), and 2-([2,2′-bipyridin]-6-yl)-4,6-dimethylphenol (BpyPh 2,4-Me -H) have been synthesized and applied to mediate the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) and l-lactide (L-LA) in the presence of benzyl alcohol. The living characters of predictable molecular weight, narrow molecular weight distribution, and the formation of block copolymer were observed in the polymerization mediated by (BpyPh 2,4-tBu )AlMe 2 and all three complexes associated with benzyl alcohol could initiate the ROP of ε-CL and L-LA. The iso-selectivity of rac-lactide polymerization could be enhanced from P m = 0.38 to P m = 0.75 by increasing the steric hindrance of ortho-substituent on phenol group of the ligand.