Multicomponent Polymerizations of Elemental Sulfur, CH₂Cl₂, and Aromatic Amines toward Chemically Recyclable Functional Aromatic Polythioureas

The exploration of new polymer materials required the development of efficient, economic, robust, and scalable synthetic routes, taking energy consumption, environmental benefit, and sustainability into overall consideration. Herein, through retro-polymerization analysis of functional aromatic polythioureas, a multicomponent reaction of elemental sulfur, CH₂Cl₂, and aromatic amines was designed with the assistance of fluoride, and efficient, economic, and robust multicomponent polymerizations (MCPs) of these three abundantly available cheap monomers, elemental sulfur, CH₂Cl₂, and aromatic diamines, were developed to realize scalable conversion directly from sulfur to a series of functional aromatic polythioureas with high molecular weights (<i>M</i>_n up to 50,800 g/mol) in excellent yields (up to 98%). The synergistic cooperation of the strong and selective coordination of thiourea with gold ions and the redox property of aromatic polythiourea enable in situ reduction of Au³⁺ to elemental gold under a normal bench condition. Furthermore, the functional aromatic polythiourea could be chemically recycled through aminolysis with NH₃·H₂O to afford a diamine monomer in 83% isolated yield. The development of elemental sulfur-based MCP has brought the opportunity to access cost-effective and sustainable sulfur-containing functional polymer materials, which is anticipated to provide a solution for the utilization of sulfur waste and making profitable polymer materials.