A Dithio Vinylthio C 2 Synthon Enabling Crystalline and Luminescent Sulfur‐Decorated Polymers

ABSTRACT While thioether linkages are commonly associated with soft and amorphous polymer backbones, herein, we show that a calcium carbide‐derived α,ω‐bis(vinylthio) synthon enables crystalline, sequence‐defined sulfur polymers with nonconventional luminescence. A single‐step thiol–yne addition reaction uses acetylene generated in situ from industrial calcium carbide (CaC 2 ) to produce a modular C 2 vinyl sulfide (also known as vinylthio) monomer that undergoes quantitative, light‐induced thiol‐ene step‐growth polymerization with aliphatic dithiols. Type I photoinitiation ensures complete anti‐Markovnikov addition to give C 2 ‐segmented poly(thioether)s, while thermal and base‐mediated conditions generate hybrid poly(thioether)/polydisulfide structures. The resulting sulfur‐rich backbones display sharp melting transitions, spherulitic crystallization, one‐step thermal decomposition up to about 316°C, and pronounced cluster‐triggered emission arising from dense thioether clustering and through‐space conjugation. Green metric analysis reveals high Atom Economy and essentially waste‐free polymer formation, thereby linking efficient use of an established C 2 synthon to precision sulfur polymer design. This C 2 vinylthio platform provides a general strategy to convert classically soft thioether motifs into structurally ordered and luminescent materials, and establishes vinyl sulfides as powerful, yet underutilized, building blocks in sustainable polymer chemistry.