Catalysts composed of rare earth compounds, (iso-Bu)3Al, and water were developed for the preparation of poly(lactic acid). D,L-Lactide could be polymd. into poly(lactic acid) with high yield and controllable mol. wt. in PhMe solution using the above catalysts.

Key words: LACTIC ACID, WATER, ALUMINIUM ALKYLS, X-RAY DIFFRACTION ANALYSIS, RARE EARTH METAL COMPLEX, POLYMERISATION CATALYST, RING OPEN POLYMERIZATION, VISCOSITY AVERAGE MOLECULAR WEIGHT