Polymerization of Aliphatic Cyclic Ester using Iron Compounds as Catalysts

Ring-opening polymerization of L-Lactide(L-LA) and copolymerization of L-LA and ε-caprolactone (ε-CL) using iron complexes as catalysts were investigated. The effects of temperature, time and catalyst amount etc. were studied. The polymeric products were characterized by GPC, 1H-NMR , ICP-AES and DSC. The polymerization mechanism was explored. Results show that iron(Ⅲ) acetylacetonate (Fe(acac)3) and iron(Ⅱ) acetylacetonate (Fe(acac)2) are the more efficient catalysts, since the monomer conversion was up to 90%; the number average molecular weight of the product is 1.2×105 and the molecular weight distribution (Mw/Mn) is 1.4. Fe(acac)3 is also an effective catalyst for copolymerization of L-LA and ε-CL.