Catalytic ring-opening polymerization of l-lactide by titanium biphenoxy-alkoxide initiators

Abstract

Six different titanium biphenolate complexes were synthesized and investigated as initiators for the ring opening polymerization of l-lactide in the bulk phase but typically below the degradation temperature of the monomer. All the titanium complexes are effective in forming polylactide with good conversions. The nature and steric bulk of the phenolic ligands coordinated to the central titanium greatly influence polymer properties. In all cases the PLA obtained display low molecular weights and narrow disperisities. Both 1H and 13C NMR spectra indicate the polymers to be essentially isotactic in nature. High crystallinity and controlled morphology of polylactides are uniquely different compared to conventional high molecular weight PLA obtained with tin based initiator.