Multicomponent Polymerizations Provide Sustainable Sulfur (Selenium)-Containing Polyesters

ConspectusWith the rapid development of the polymer industry, the contradiction between synthetic polymers and the sustainable development of human society is becoming more and more prominent. The advancement of degradable plastics greatly contributes to the sustainability of our society. Synthetic polymers containing precisely placed in-chain ester groups are expected to be degradable in a controlled manner. Their potential as environmentally benign plastics is significant. For this purpose, there is a clear need for their improved performance. Incorporating sulfur functional groups into polyesters can improve the diverse crucial properties of their counterparts. However, there is a lack of related high-efficiency polymer synthesis methods.In response to this issue, we designed a series of multicomponent polymerization methods for the synthesis of a library of degradable polyesters with tunable structure and properties. This Account summarizes our recent efforts to discover the polymerization approach. The method uses readily available monomers including diols, diamines, H₂O, diacrylates, carbonyl sulfide (COS), cyclic thioanhydrides, CO, and selenium powder. The polymerization is usually carried out under mild conditions: at 60 to 90 °C, for 2 to 12 h, using organobases as the catalysts or catalyst-free. This approach achieves the simultaneous incorporation of in-chain ester and sulfur/selenium functional groups including thiocarbonate, thioether, thioester, thiourethane, and selenoether.The method has a wide monomer scope and yields diverse polymers with tunable structures. The obtained polyesters possess weight-average molecular weights of up to 175.4 kDa. Most of these polyesters are thermally stable, exhibiting decomposition temperatures of >200 °C. Due to the diversity of structure, these polymers demonstrate extensively tunable performance covering crystalline plastics, thermoplastic elastomers, and amorphous plastics. These polymers exhibit a wide range of glass-transition temperatures of -60 to 72 °C and a wide range of melting temperatures of 43 to 274 °C. Notably, the polymers containing long alkyl chains (number of carbon atoms ≥ 9) exhibit polyethylene-like crystallinity and mechanical properties. The in-chain thiourethane or amide groups enable enhanced thermal and mechanical properties due to the incorporation of inter/intramolecular hydrogen bonding. These polymers are also easy to degrade via alkali hydrolysis, alcohol hydrolysis, enzymatic hydrolysis, oxidation, etc. The degradation products often have well-defined structure and value-added properties and can even be directly used for repolymerization to achieve a closed-loop chemical cycle. Overall, the multicomponent polymerization presented in this Account furnishes a facile and versatile synthesis of sustainable polymers with tunable structure and properties.