Thioamides on Radical-Chain Growth Monomers: Postpolymerization Transformation for Tailored Functional Polymers

Abstract

Thioamides cannot be easily incorporated into radical chain-growth polymers because they react rapidly with propagating radicals, preventing vinyl monomers bearing thioamides from undergoing efficient radical polymerization. As a result, thioamide-containing polymers are largely restricted to step-growth strategies or inefficient post-polymerization thionation methods. Here, we address this limitation using thioimidates as radical-compatible precursors to thioamides. Thioimidatefunctionalized monomers undergo conventional free-radical copolymerization to give linear and crosslinked copolymers, demonstrating that thioimidate groups are compatible with radical chain-growth conditions. Subsequent treatment with NaHS converts thioimidates to thioamides within minutes at room temperature, producing only gaseous by-products and avoiding the heterogeneous side reactions associated with traditional sulfurizing reagents. The resulting thioamide-functional copolymers are characterized, and their ability to bind gold from aqueous solution is demonstrated as a proof of concept rather than an optimized recovery process. Together, these results establish a general strategy for accessing thioamide-functional chain-growth copolymers and highlight thioimidates as a versatile platform for post-polymerization conversion to thioamides.