Azopyrazole boronic ester crosslinks with long thermal half-lives for phototunable viscoelastic hydrogels
- 1Department of Chemistry, Northwestern University, 2145 Sheridan Rd, Evanston, IL, United States of America, 60208
Abstract
Covalent adaptable networks (CANs) based on boronic acid–ester exchange undergo rapid network reconfiguration in ambient conditions, making them useful materials for biomedical applications. The combination of photoswitches and dynamic bonds imparts reversible spatiotemporal control over mechanical properties for smart and responsive materials. Here, we report azopyrazole boronic acids that undergo rapid photoisomerization to their metastable Z isomers, which have extremely long thermal half-lives (over a year at 25 °C) and a 3-fold enhancement in binding affinity for diols compared to the E isomer. When incorporated into hydrogels, these photoswitchable dynamic bonds enable reversible changes in stiffness and stress relaxation time with at least 6 cycles of visible and UV light. Despite only containing dynamic crosslinks, these hydrogels are comparable in stiffness to our previously reported hybrid materials containing dynamic azobenzene boronic ester and static bis(acrylamide) crosslinks. This work demonstrates an alternative strategy to tuning boronic acid-ester equilibria with light while maintaining strong binding in both isomers.
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BibTeX
@misc{paterson2026azopyrazole,
title = {{Azopyrazole boronic ester crosslinks with long thermal half-lives for phototunable viscoelastic hydrogels}},
author = {Mara L. Paterson and Tomas Castillo and Sarah Lin and Julia A. Kalow},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008994/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008994/v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Azopyrazole boronic ester crosslinks with long thermal half-lives for phototunable viscoelastic hydrogels
AU - Mara L. Paterson
AU - Tomas Castillo
AU - Sarah Lin
AU - Julia A. Kalow
PY - 2026
DA - 2026/09/17
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008994/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008994/v1
AB - Covalent adaptable networks (CANs) based on boronic acid–ester exchange undergo rapid network reconfiguration in ambient conditions, making them useful materials for biomedical applications. The combination of photoswitches and dynamic bonds imparts reversible spatiotemporal control over mechanical properties for smart and responsive materials. Here, we report azopyrazole boronic acids that undergo rapid photoisomerization to their metastable Z isomers, which have extremely long thermal half-lives (over a year at 25 °C) and a 3-fold enhancement in binding affinity for diols compared to the E isomer. When incorporated into hydrogels, these photoswitchable dynamic bonds enable reversible changes in stiffness and stress relaxation time with at least 6 cycles of visible and UV light. Despite only containing dynamic crosslinks, these hydrogels are comparable in stiffness to our previously reported hybrid materials containing dynamic azobenzene boronic ester and static bis(acrylamide) crosslinks. This work demonstrates an alternative strategy to tuning boronic acid-ester equilibria with light while maintaining strong binding in both isomers.
ER -