Multicomponent Polymerization of Sulfur, Diynes, and Aromatic Diamines and Facile Tuning of Polymer Backbone Structures

Polythioamides have attracted growing research interests owing to their structural similarity to extensively applied high-performance polyamide analogues, together with the additional properties endowed by sulfur such as strong metal coordination ability, high light refractivity, and unique photophysical properties. The synthesis of polythioamides, especially aromatic polythioamides, remained challenging due to the poor reactivity of aromatic amine monomers. In this work, through activation of sulfur by KF, a multicomponent polymerization (MCP) of elemental sulfur, aromatic diynes, and aromatic diamines was developed in the presence of KF in DMSO at 100 °C, affording aromatic polythioamides in high yields. Small molecular model reaction study suggested that under the reaction conditions, terminal alkyne could react with sulfur and aromatic amine to afford both thioamide and thiourea, depending on the loading ratio of alkyne and amine. With these competitive polymerization pathways, the backbone structures of the MCP product could be facilely tuned by simply changing the monomer loading ratio of diynes and diamines, producing random poly(thioamide-thiourea)s with decent molecular weights (Mns) of up to 19,200 g/mol in high yields of up to 98%. Through the polymer backbone structural tuning, the polymer thermal properties, including decomposition temperatures and glass transition temperatures, could be adjusted. The MCP has hence demonstrated facile synthesis of polythioamides and simple tuning of the backbone structure and property of sulfur-containing polymer materials.