Synthesis of long-chain aliphatic poly(β-thioester)s via thiol-Michael polyaddition and their applications in noble metal recovery and information encryption

Long-chain aliphatic polyesters are recognized as the most promising polyethylene mimics in that these materials show comparative physicochemical properties to polyolefins and own the unique merits of degradability and/or recyclability. Nevertheless, the application scenarios of these polymers are rather limited owing to the lack of functional groups. Herein, sulfur atoms are incorporated into the microstructures of long-chain aliphatic polyesters to decipher the variations of physicochemical properties upon replacing specific methylene units by thioether moieties and simultaneously impart polyethylene-like materials with functionalities. First of all, high molecular weight polyesters P1 - P4 and poly(β-thioester)s P5 - P8 were obtained via condensation polymerization and thiol-Michael polyaddition, respectively. As for phase transition behaviors, poly(β-thioester)s show inferior crystallization/melting temperatures and the corresponding enthalpy changes than their polyester counterparts, and a loosely packed crystalline structure should be responsible for such thermal property degradation. It is reasonable that replacing specific methylene units of long-chain aliphatic polyesters by sulfur atoms, the much bulkier functional entities, will definitely cause great disturbance to the regular arrangement of polymer chains. The rapid hydrolytic degradation of poly(β-thioester)s in acidic and alkaline media can be ascribed to the easy penetration of water molecules into their incompact amorphous/crystalline regions. In the meantime, these poly(β-thioester)s exhibit great prospects in noble metal recovery and information encryption (optical anticounterfeiting). For instance, poly(β-thioester) P5 is an excellent adsorbent to abstract gold ions from water due to its outstanding metal coordination capability. Moreover, poly(β-thioester) P5 emits bright blue photoluminescence in concentrated solution and solid state upon UV irradiation as a result of the clustering-triggered through space electron delocalization and rigidified polymer chain conformation.