Harnessing Strained Disulfides for Photocurable Adaptable Hydrogels

We report a photomediated disulfide cross-linking strategy for the generation of adaptable hydrogels from telechelic network precursors containing strained cyclic disulfides. Exploiting the intricate stereoelectronic properties of 1,2-dithiolanes arising from the unfavorable four-electron interaction in the disulfide scaffold, amphiphilic poly(ethylene glycol)-1,2-dithiolane conjugates formed free-standing adaptable hydrogels at 10 wt % polymer content upon disulfide photolysis under UV irradiation (lambda(max) = 365 nm). Cross-linking was achieved in less than 10 min with tunable network moduli depending on irradiation time. Investigations into the gelation mechanism suggest the formation of free thiols during light exposure accounting for the dynamic nature of the gels. Furthermore, we successfully expanded this gelation strategy to green light (lambda(max) = 515 nm) by employing the photosensitizer eosin Y, allowing for hydrogel formation open to air.