Synthesis of Polythioimide from Polyimide via Sulfur–Oxygen Exchange Reaction and Fabrication of Their Multifunctional Fibers

Polythioimides (PTIs), a class of sulfur-containing polymers, can theoretically be obtained via the sulfur–oxygen exchange reaction of polyimides (PIs), but their synthesis remains a challenge. Here, we report a versatile strategy that overcomes this limitation by introducing low-polarity alkyl side chains into a hydroxyl-containing polyimide precursor via postesterification. This approach enables homogeneous sulfur–oxygen exchange and achieves complete conversion from PI to PTI. The resulting PTI combines excellent thermal stability, solution processability, and abundant electron-rich thioimide groups. These groups act as both high-affinity coordination sites and intrinsic reductants, enabling selective adsorption of precious metal ions (92.3% for Au 3+ and 80.1% for Pd 2+ in mixed systems) followed by in situ spontaneous reduction to zerovalent metal nanoparticles (2–4 nm). Leveraging its good spinnability, PTI is fabricated into nanofibrous membranes. The in situ-generated Pd 0 nanoparticles serve as self-supported, highly active catalysts for the rapid decolorization of pollutants such as azo dyes and p-nitrophenol. Moreover, the PTI matrix itself generates multiple reactive oxygen species (•O 2 –, •OH, and 1 O 2 ) via a photoinduced pathway under visible light, achieving nearly 100% antibacterial activity against E. coli and S. aureus . This work not only provides a practical synthetic route to polythioimides but also establishes a class of multifunctional polymer for precious metal recovery, heterogeneous catalysis, and photodynamic antibacterial therapy.