Synthesis, selective decoration and photocrosslinking of self-immolative poly(thioester)-PEG hydrogels

Self-immolative polymers are a class of polymers that undergo linear depolymerization of the main chain, often triggered by a single initial degradation event. Chain-unzipping immolation processes followed by low-ceiling-temperature polymers yield regenerated monomers, demonstrating the remarkable potential of these polymers in the development of reversible and recyclable materials. In this work, we describe the synthesis of an amino-acid-derived poly(thioester) self-immolative polymer with pendent functional groups allowing for selective decoration of the polymer backbone with solubilizing and reactive functional groups for subsequent post-polymerization modification. Crosslinking norbornene-functionalized, water-soluble derivatives of these polymers via the thiol-ene photoclick reaction yielded mechanically robust hydrogels within 15 s of light exposure. These networks were capable of immolation in response to deprotonation of an end-capping thiol, unzipping along the poly(thioester) backbone to yield constituent monomers and larger molecular weight crosslinker fragments. Finally, degelation rates were controlled with pH and temperature in aqueous buffers. At physiological pH and temperature, complete degradation of approximately 20 wt% hydrogels was observed after 16 h, and raising the buffer pH to 10 resulted in network dissolution within 5 h. (c) 2022 Society of Industrial Chemistry.

Automated summary

This study describes the synthesis of a self-immolative polymer derived from amino acids and the subsequent functionalization of the polymer backbone through post-polymerization modification. The resulting polymer can be crosslinked to form mechanically robust hydrogels using a photoreactive thiol-ene reaction, and the hydrogels can undergo self-immolation under specific conditions.