The Structural Effect of Hydrogen Bond Donors Within the Anion Structure of Ionic Liquids on the Ethanolysis Efficiency of Polycarbonate

Polycarbonate (PC) ethanolysis using ionic liquids (ILs) offers an ecofriendly recycling method that enables the recovery of bisphenol A (BPA) without the need for newly synthesized BPA, a xenoestrogen used in PC polymerization. Depolymerization efficiency is strongly influenced by the structure of ILs. This study investigates the effect of the IL anion structure on the depolymerization efficiency by focusing on the role of hydrogen bond-donating functional groups. We examined the depolymerization performance and intermolecular interactions of three ILs (1-ethyl-3-methylimidazolium acetate [EMIM][Ac], 1-ethyl-3-methylimidazolium glycolate [EMIM][Ga], and 1-ethyl-3-methylimidazolium lactate [EMIM][La]). Among them, [EMIM][La] exhibited the highest depolymerization efficiency (100% PC conversion, 99.9% BPA yield, and 95% BPA purity) at 90°C for 8 h. This superior efficiency was attributed to the spatially accessible hydroxyl group of the lactate anion. Furthermore, [EMIM][La] maintained its catalytic activity during five consecutive recycling cycles, demonstrating its reusability. These findings could help design efficient IL catalysts for polymer depolymerization.