Heterocyclic-dithiol click chemistry

A polymer derived from a first monomer and a first cross-linker, wherein

• the first monomer comprises at least two thiol functional groups;
• the first cross-linker comprises a moiety of Formula I:
• wherein
• W is S;
• Y is S(O);
• X together with W and Y forms a substituted or unsubstituted 3-10-membered heterocyclic ring,
• the first monomer is selected from the group consisting of poly(ethylene glycol) dithiol, 4arm-PEG2K—SH, 4arm-PEG5K—SH, 4arm-PEG10K—SH, 4arm-PEG20K—SH, 4-arm poly(ethylene oxide) thiol-terminated, 8arm-PEG10K—SH (hexaglyerol core), 8arm-PEG10K—SH (tripentaerythritol core), 8arm-PEG20K—SH (hexaglyerol core), 8arm-PEG20K—SH (tripentaerythritol core), and 8-arm poly(ethylene oxide) thiol-terminated, and
• the polymer is a hydrogel.