Single-crystalline Poly(disulfide)s Enabled by Photo-Triggered Topochemical Ring-Opening Polymerization of an 1,2-Dithiolane

Constructing single-crystalline polymers is fundamentally challenging due to the polydispersity and conformational com-plexity of synthetic polymers. Topochemical polymerization offers a versatile approach to single-crystalline polymers by in situ polymerization of pre-organized monomers at the solid state. However, the existing examples of topochemical polymerization relies on the formation of strong covalent bonds (e.g. C-C, C-N and C-O), while the construction of single-crystalline polymers based on weak yet dynamic covalent bond, e.g. disulfide bonds, remains elusive. Here we report a single-crystalline poly(disulfide) by photo-triggered topochemical ring-opening polymerization of an 1,2-dithiolane mediated by disulfide exchange. The key design is to control the spatial distance and geometry of 1,2-dithiolane ring by elaborating sidechain H-bonding moieties that determines the supramolecular self-assembling architecture of monomeric crys-tals. It is found that zigzag-like preorganization of 1,2-dithiolanes facilitates the quantitative single-crystal-to-single-crystal polymerization triggered by UV/visible light or X-ray. The resulting single-crystalline poly(disulfide)s exhibits superior thermostability and solvent resistance compared to the state-of-the-art amorphous or semicrystalline poly(disulfide)s made from conventional melting or solution-based methodologies. Upon dissolving the crystals with trifluoracetic acid, the intrinsic dynamicity of poly(disulfide)s could be reactivated to enable polymer-to-monomer depolymerization and yield origin-quality crystalline monomers for polymer regeneration. We anticipate that this work represents a starting point bridging dynamic polymers with topochemical polymerization towards dynamic molecular crystals and smart materials.