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This paper studies a polymer network in which crosslinks are degradable but polymer chains are not. We show that entanglements markedly enhance the mechanical properties of the polymer network before degradation and slow down degradation. We synthesize polyacrylamide hydrogels with disulfide crosslinks. In a precursor of a low water-to-monomer molar ratio and low crosslinker-to-monomer molar ratio, the monomers are crowded and the resulting polymer chains are long, so that the entanglements greatly outnumber crosslinks. The as-synthesized hydrogels are submerged in pure water to swell to equilibrium. We show that entanglements enhance the swell resistance of the hydrogel, as well as stiffen and toughen the hydrogel. We further show that entanglements slow down degradation when the hydrogel is submerged in an aqueous solution of cysteine. This work demonstrates that entanglements substantially expand the properties space of degradable polymers.
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This content will become publicly available on February 28, 2026
Development of Bioorthogonally Degradable Tough Hydrogels Using Enamine N-Oxide Based Crosslinkers
Inducibly degradable polymers present new opportunities to integrate tough hydrogels into a wide range of biomaterials. Rapid and inducible degradation enables fast transition in material properties without sacrificing material integrity prior to removal. In pursuit of bioorthogonal chemical modalities that will enable inducible polymer degradation in biologically relevant environments, enamine N-oxide crosslinkers are developed for double network acrylamide-based polymer/alginate hydrogels. Bioorthogonal dissociation initiated by the application of aqueous diboron solution through several delivery mechanisms effectively lead to polymer degradation. Their degradation by aqueous B2(OH)4 solution results in a fracture energy half-life of <10 min. The biocompatibility of the degradable hydrogels and B2(OH)4 reagent is assessed, and the removability of strongly adhered tough hydrogels on mice skin is evaluated. Thermoresponsive PNiPAAm/Alg hydrogels are fabricated and application of the hydrogels as a chemically inducible degradable intraoral wound dressing is demonstrated. It is demonstrated through in vivo maximum tolerated dose studies that diboron solution administered to mice by oral gavage is well tolerated. Successful integration of enamine N-oxides within the tough double network hydrogels as chemically degradable motifs demonstrates the applicability of enamine N-oxides in the realm of polymer chemistry and highlights the importance of chemically induced bioorthogonal dissociation reactions for materials science.
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- PAR ID:
- 10576094
- Publisher / Repository:
- Wiley-VCH GmbH
- Date Published:
- Journal Name:
- Advanced materials
- ISSN:
- 1521-4095
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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