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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 CH acidity.
Kricheldorf et al. (Sun,) studied this question.