Metal-Free Sulfur-Dots Induced Spatiotemporal PhotoRDRP for Multi-Arm Star Functional Polymer

Sulfur-dots (S-dots) serve as a cost-effective and non-toxic alternative to traditional photocatalysts or transition metals typically required in photoinduced reversible deactivation radical polymerization (photoRDRP). Herein, we report a facile and efficient method for synthesizing well-defined multi-arm star polymers through S-dots mediated photoRDRP under ambient conditions. This approach enables precise control over polymer growth with excellent spatiotemporal control over polymerization, as evidenced by the ability to pause and resume polymerization with UVA light ("ON/OFF" switching). This methodology was successfully applied to produce a variety of polymer architectures, including multi-arm star homopolymers and dual-responsive diblock and triblock copolymers. Among these, the synthesized 4-arm star [poly(N,N-dimethyl acrylamide)-block-poly(dimethyl amino ethyl methacrylate)-block-poly(butyl acrylate)]₄-Br [4-arm star (PDMA-b-PDMAEMA-b-PBA)₄-Br] triblock copolymer was used to assess pH and temperature responsiveness. This work introduces a sustainable, metal-free route for the development of next-generation smart polymers suitable for biomedical and environmental applications and highlights the versatility of S-dots as a catalyst.