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Issue 35, 2016
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A comparative study of the mechanical properties of hybrid double-network hydrogels in swollen and as-prepared states

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Abstract

Significant efforts have been made to develop highly tough hydrogels towards many scientific and industrial applications. However, most of the as-prepared tough hydrogels lose their mechanical strength and toughness when they swell in aqueous solution. Current knowledge about the swelling-induced mechanical property changes mainly stems from single-network (SN) hydrogels and chemically linked double-network (DN) hydrogels, but little is known about the swelling mechanical properties of hybrid physically–chemically linked DN gels. Here, we synthesized hybrid agar/PAM DN hydrogels combining a physically cross-linked first network of agar and a covalently cross-linked second network of polyacrylamide (PAM), with particular attention paid to the relationship between the swelling and mechanical properties of the hydrogels. The optimal agar/PAM DN gels achieved a tensile stress of ∼1.0 MPa and a toughness of ∼3988 J m−2 in the as-prepared state and a tensile stress of 1.4 MPa and a toughness of ∼3960 J m−2 in the swollen state. The agar/PAM DN gels can readily achieve swelling ratios in the range of ∼1.3–3.6 by adjusting the concentrations of the first network, the second network, and the crosslinker. The swelling capacity of the agar/PAM DN gels was balanced by the competition between the “non-swellable” agar network and the “highly swellable” PAM network, indicating that the first and second networks play different roles in the swelling-induced mechanical properties of the agar/PAM gels. Based on a comparison of the tearing and tensile behaviors of the hybrid DN gels between both as-prepared and swollen gels, we proposed a swelling-induced fracture mechanism that is different from those of SN and chemically-linked DN hydrogels. This work not only demonstrates a very tough swollen DN gel with a hybrid network, but also provides a better understanding of the swelling characteristics of hybrid DN gels, which hopefully helps to offer some valuable insights into the development of next-generation tough hydrogel materials in both as-prepared and swollen states.

Graphical abstract: A comparative study of the mechanical properties of hybrid double-network hydrogels in swollen and as-prepared states

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Publication details

The article was received on 20 Jun 2016, accepted on 02 Aug 2016 and first published on 03 Aug 2016


Article type: Paper
DOI: 10.1039/C6TB01511E
Citation: J. Mater. Chem. B, 2016,4, 5814-5824
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    A comparative study of the mechanical properties of hybrid double-network hydrogels in swollen and as-prepared states

    H. Chen, F. Yang, R. Hu, M. Zhang, B. Ren, X. Gong, J. Ma, B. Jiang, Q. Chen and J. Zheng, J. Mater. Chem. B, 2016, 4, 5814
    DOI: 10.1039/C6TB01511E

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