ma5b02592_si_001.pdf (198.55 kB)
Yielding Criteria of Double Network Hydrogels
journal contribution
posted on 2016-02-12, 00:00 authored by Takahiro Matsuda, Tasuku Nakajima, Yuki Fukuda, Wei Hong, Takamasa Sakai, Takayuki Kurokawa, Ung-il Chung, Jian Ping GongDouble network (DN) gels, consisting
of a brittle first and flexible
second network, have been known to be extremely tough and functional
hydrogels. In a DN gel subjected to force, the brittle first network
breaks prior to the fracture of the flexible network. This process,
referred to as internal fracture, dissipates energy and increases
the energy required to completely fracture DN gels. Such internal
fracture macroscopically appears as a yielding-like phenomenon. The
aim of this paper is to investigate the relationship between the yield
point and the first network molecular structure of DN gels to more
deeply understand the internal fracture mechanism of DN gels. To achieve
this goal, we synthesized DN gels having a tetra-PEG first network,
which is known to be a nearly ideal and well-controlled network gel.
We have found that yielding of the DN gels occurs when the first network
strands reach their extension limit (finite extensibility), regardless
of their deformation mode. This conclusion not only helps by further
understanding the toughening mechanism of DN gels but also allows
for the design of DN gels with precisely controlled mechanical properties.