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Preferential Control of Forward Reaction Kinetics in Hydrogels Crosslinked with Reversible Conjugate Additions

preprint
submitted on 07.02.2020, 16:47 and posted on 10.02.2020, 13:02 by Thomas FitzSimons, Felicia Oentoro, Tej V. Shanbhag, Eric Anslyn, Adrianne Rosales

Molecular substitutions were used to demonstrate preferential control over the kinetic rate constants in a poly(ethylene glycol)-based hydrogel with two different reversible thia-conjugate addition reactions. A strong electron withdrawing nitrile group on the conjugate acceptor showed a 20-fold increase in the forward rate constant over a neutral withdrawing group, while the reverse rate constant only increased 6-fold. Rheometry experiments demonstrated that the hydrogel plateau modulus was primarily dictated by reaction equilibrium, while the stress relaxation characteristics of the hydrogel were dominated by the reverse rate constant. Furthermore, the dynamic crosslinking allowed the hydrogel to rapidly and spontaneously self-heal. These results indicate that decoupling the kinetic rate constants of bond exchange allow systematic control over dynamic covalent hydrogel bulk properties, such as their adaptability, stress relaxation ability, and self-healing properties.

Funding

NSF MRSEC DMR-1720595

Burroughs Wellcome Fund CASI-1015895

History

Email Address of Submitting Author

arosales@che.utexas.edu

Institution

University of Texas at Austin

Country

United States

ORCID For Submitting Author

0000-0003-0207-7661

Declaration of Conflict of Interest

No conflict of interest

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