STUDIES ON THE RING-OPENING POLYMERIZATION OF D,L- LACTIDE BY USING IRON(III) ACETYLACETONATE AS CATALYST

Iron(Ⅲ) acetylacetonate [Fe(acac) 3] was used as catalyst for the ring-opening polymerization of D,L-lactide and copolymerization of D,L-lactide with polyethylene glycol (PEG).The effects of catalyst content,reaction temperature,polymerization time and D,L-lactide/PEG molar ratio were investigated.It was showed that the polymerization conversion of lactide more than 90% could be obtained and polylactide (PDLLA) with viscosity-average molecular weight up to 66000 was prepared.Experimental results indicated that the ring-opening polymerization of lactide proceeded via a coordination-insertion mechanism.Analysis by 1H-NMR showed that PEG acted as an initiator participated in initiation of the ring-opening polymerization of lactide, while Fe(acac) 3 promoted the esterification of PEG with lactide.The lactide chains grew from both ends of the PEG molecules and ended with hydroxy-terminated lactyl units.