Ring-opening polymerization of L-lactide by using sodium complexes bearing amide as catalysts in high polar solvent

In this study, a series of sodium complexes with amidate ligands, including sulfonamide, acylamide, and aryl carbamate, were synthesized. These sodium complexes were used as catalysts to study the L-lactide (LA) polymerization in high polar solvent (dimethyl sulfoxide: tetrahydrofuran = 1:4). Among these sodium complexes, C^TolOMe-Na (5) exhibited the highest catalytic activity (10 s, conversion > 99% with the ratio [LA]:[C^TolOMe-Na (5)]:[BnOH] = 800:1:120, [C^TolOMe-Na (5)] = 1.25 mM at 0 °C) and controllability (Đ = 1.10). To prove that C^TolOMe-Na (5) can polymerize LA with special initiators in polar solvent, 1,4-benzenedimethanol and pentaerythritol were used as initiators in LA polymerization. The polymerization results revealed that end-chain-modified poly(lactides) with a precise molar mass (Mn_GPC: 3000–8800) and narrow dispersity (1.04–1.28) can be synthesized.