Bulk Polymerization of L-lactide with Mixed Aluminum Organometallic Catalysts

The differences between single and mixed aluminium catalyst systems in the bulk polymerization of L-lactide were studied. Al(O-i-Pr)(3), TMA, TOA and TIBA were employed for the mixed-catalyst systems, and TIBA was chosen as a reference catalyst. For the Al(O-i-Pr)(3)/TIBA catalyst system, the conversion of polymerization increased as the composition of Al(O-i-Pr)(3) in the mixed catalyst increased. The molecular weight of the resulting PLA reached to about 13000 g/mol, and the polydispersity index of the polymer from the Al(O-i-Pr)(3)/TIBA catalyst was slightly increased than that of single catalyst. The higher molecular weight tail or shoulder was revealed in the GPC curve. The conversion of the TOA/TIBA catalyst system decreased as the composition of TOA in the mixed catalyst increased. The molecular weight of PLA prepared with TOA/TIBA catalysts increased up to 14000 g/mol. The Al compounds-mixed catalysts could produce a higher molecular weight tail or shoulder in the GPC curve, which may result in enhancement of mechanical properties of PLA.