Economic Sulfur Conversion to Functional Polythioamides through Catalyst-Free Multicomponent Polymerizations of Sulfur, Acids, and Amines

Sulfur utilization is a global concern because of its abundant nature sources and the safety or environmental problems caused by its burning or oxidation during storage, while sulfur-containing polymers are popular materials in virtue of their fascinating properties such as metal coordination ability, high refractive indices, and semiconducting property. The synthesis of sulfur-containing polymers is challenging, especially directly from elemental sulfur. Herein, catalyst-free and scalable multicomponent polymerizations (MCPs) of all commercially available elemental sulfur, dicarboxylic acids, and diamines were reported to facilely construct 12 polythioamides with diverse and well-defined structures, high molecular weights (<i>M</i>_w's up to 86 200 g/mol), and excellent yields (up to 99%) from elemental sulfur. Besides commonly used aliphatic diamines, aromatic diamine monomers are also applicable to these multicomponent polymerizations, affording polythioamides with unique rigid structures and improved functionality as compared to those of the previously reported polythioamides. These polythioamides can be applied in gold recovery, which could extract a trace amount of Au³⁺ from practical acidic leaching solution of discarded electronic waste selectively, rapidly (1 min), sensitively (10 ppb), and efficiently (>99.99%) with high extraction capacity up to 0.60 g· Au³⁺/g to directly afford high-purity elemental gold after pyrolysis. The MCPs could make use of both abundantly existing sulfur waste and trace amounts of precious gold residue in electronic wastes, demonstrating their great potential in resource utilization.