Polylactones, 38. Polymerization of L‐lactide with Fe(II) lactate and other resorbable Fe(II) salts

Abstract Commercial FeCl 2 and Fe(II) glycolate, Fe(II) L ‐lactate or Fe(II) L ‐mandelate were used as initiators for the polymerization of L ‐lactide. All polymerizations were conducted in bulk at 150°C, because no conversion was observed in bulk at 120°C. The Fe(II) lactate was found to be more reactive than FeCl 2 , and it yielded slightly higher molecular weights than all other initiators. Under the optimum conditions, viscosity average molecular weights ( M̄ v ) around 50 000 and yields above 90% were obtained. However, slight racemization (2–5%) of the isolated poly(L‐lactide) was also observed under most circumstances. Characterization of unreacted monomer proved that the racemization mainly involves the monomeric lactide due to its higher CH acidity.