Sulfur as a molecular language for circular materials

Sulfur chemistry enables reversible, redox-active, exchangeable, and stimulus-responsive transformations across diverse polymer systems. Yet these chemistries are often treated as independent reaction classes. This opinion article proposes that sulfur functions as a molecular language whose chemical ‘instructions' program synthesis, adaptation, repair, transformation, disassembly, recycling, and remanufacturing across material lifecycles. Recent advances in dynamic sulfur exchange, reversible polymerization, sequence-controlled sulfur incorporation, and chemical upcycling illustrate how these molecular processes can be translated into material-level behavior. Rather than viewing sulfur solely as a feedstock or functional group, we propose its broader consideration as a molecular design principle for integrating performance, adaptability, and circularity from the outset of polymer design.