Ring-Opening Polymerization to Access Chemically Recyclable Aromatic Poly(thio)carbonates

Aromatic polycarbonates are attractive, high-performance thermoplastic materials. However, it is still a formidable challenge to achieve economical and promising chemical recycling of aromatic polycarbonates. Herein, we prepared two benzo-fused seven-membered cyclic thiocarbonate monomers (M1 and M2) with different sulfur atoms to construct chemically recyclable aromatic poly(thio)carbonates. These monomers underwent efficient DBU-catalyzed polymerization even with a catalyst loading of 0.01 mol %. The resulting aromatic poly(thio)carbonate P(M1) was a semicrystalline material with a T_m of 131 °C, while P(M2) was amorphous with a T_g of 48 °C. In comparison with the commercial aromatic polycarbonates, they showcased enhanced refractive index (n_D = 1.64/1.71), manifesting the benefit of sulfur incorporation into the polymer material. Degradation of the poly(monothio)carbonate led to a mixture of monomer and decarboxylation product. Impressively, P(M2) illustrated efficient SnCl₂-mediated depolymerization via bulk thermal depolymerization, recovering M2 with quantitative yields (>95%).