作者：Hong Chen, Qiang Chen* and Jie Zheng *, et al.
关键字：double network hydrogels
论文来源：期刊
具体来源：J. Mater. Chem. B
发表时间：2016年
Significant efforts have been made to develop highly tough hydrogels towards many scientific and industrial applications. However, most of 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 for 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 to the relationship between 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/m2 at an as-prepared state and a tensile stress of 1.4 MPa and a toughness of ~3566 J/m2, at a swollen state, respectively. Agar/PAM DN gels can readily achieve the swelling ratios in a range of ~1.3-3.6 by adjusting the concentrations of the first network, the second network, and crosslinker. The swelling capacity of Agar/PAM DN gels was balanced by the competition between a “non-swellable” agar network and a “well swellable” PAM network, indicating that the first and second networks play different roles in the swelling-induced mechanical properties of Agar/PAM gels. Based on the comparison of tearing and tensile behaviors of 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 highly tough swollen DN gel with hybrid networks, but also provides a better understanding of swelling characteristics of the hybrid DN gels, which hopefully help to offer some valuable insights into the development of the next-generation tough hydrogel materials at both as-prepared and swollen states.