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  • Open Access

Toughness of Double Network Hydrogels: The Role of Reduced Stress Propagation

Samuel B. Walker and Suzanne M. Fielding

  • Department of Physics, Durham University, Science Laboratories, South Road, Durham DH1 3LE, United Kingdom

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Phys. Rev. Lett. 135, 188201 – Published 30 October, 2025

DOI: https://doi.org/10.1103/kck9-tc46

Abstract

Double network hydrogels show remarkable mechanical performance, combining high strength and fracture toughness with sufficient stiffness to bear load, despite containing only a low density of cross-linked polymer molecules in water. We introduce a simple mesoscale model of a double network material, detailed enough to resolve the salient microphysics of local plastic bond breakage, yet simple enough to address macroscopic cracking. Load sharing between the networks results in a delocalization of stress such that the double network inherits both the stiffness of its stiff-and-brittle sacrificial network and the ductility of its soft-and-ductile matrix network. The underlying mechanism is a reduction in the Eshelby stress propagator between sacrificial bonds, inhibiting the tendency for the plastic failure of one sacrificial bond to propagate stress to neighboring sacrificial bonds and cause a follow-on cascade of breakages. The mechanism of brittle macroscopic cracking is thereby suppressed, giving instead ductile deformation via diffusely distributed microcracking.

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Outline

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Phys. Rev. Lett. 135, 188201– Published 30 October, 2025
  • Received 14 March 2025
  • Revised 20 August 2025
  • Accepted 26 September 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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