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Abstract Double-network (DN) hydrogels, consisting of two contrasting and interpenetrating polymer networks, are considered as perhaps the toughest soft-wet materials. Current knowledge of DN gels from synthesis methods to toughening mechanisms almost exclusively comes from chemically-linked DN hydrogels by experiments. Molecular modeling and simulations of inhomogeneous DN structure in hydrogels have proved to be extremely challenging. Herein, we developed a new multiscale simulation platform to computationally investigate the early fracture of physically-chemically linked agar/polyacrylamide (agar/PAM) DN hydrogels at a long timescale. A “random walk reactive polymerization” (RWRP) was developed to mimic a radical polymerization process, which enables to construct a physically-chemically linked agar/PAM DN hydrogel from monomers, while conventional and steered MD simulations were conducted to examine the structural-dependent energy dissipation and fracture behaviors at the relax and deformation states. Collective simulation results revealed that energy dissipation of agar/PAM hydrogels was attributed to a combination of the pulling out of agar chains from the DNs, the disruption of massive hydrogen bonds between and within DN structures, and the strong association of water molecules with both networks, thus explaining a different mechanical enhancement of agar/PAM hydrogels. This computational work provided atomic details of network structure, dynamics, solvation, and interactions of a hybrid DN hydrogel, and a different structural-dependent energy dissipation mode and fracture behavior of a hybrid DN hydrogel, which help to design tough hydrogels with new network structures and efficient energy dissipation modes. Additionally, the RWRP algorithm can be generally applied to construct the radical polymerization-produced hydrogels, elastomers, and polymers.
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Constitutive and Fracture Behavior of Double‐Network Elastomers
The double‐network (DN) concept, initially applied to hydrogels, has been adapted to elastomers, resulting in materials that combine exceptional toughness with tunable elasticity. This article delves into the constitutive and fracture behaviors of DN elastomers, elucidating the pivotal role of prestretch and composition in tailoring their properties. An incompressible hyperelastic model is employed to predict the stress–strain behavior and energy release rate of a DN elastomer, focusing on how the interactions between the two networks influence its overall material properties. The influence of prestretch and composition on increasing the stiffness and energy release rate of a DN elastomer is analytically determined. The analytical predictions are validated experimentally through comprehensive mechanical and fracture testing using a DN elastomer fabricated by a two‐step crosslinking process to decouple the prestretch and composition. The results show that manipulating these processing parameters can finely tune the mechanical responses of DN elastomers, optimizing them for specific applications. The findings provide new insights into the mechanics of DN elastomers.
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- Award ID(s):
- 2403592
- PAR ID:
- 10559835
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Engineering Materials
- Volume:
- 27
- Issue:
- 2
- ISSN:
- 1438-1656
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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