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Recent Study on Double Network Gels - Molecular Stent Method and Internal Fracture Analysis

Tasuku NAKAJIMA Laboratory of Soft & Wet Matter, Hokkaido University, Sapporo, Japan

Our group has recently created double network gels (DN gels) with extremely high toughness and strength. Despite 90wt% of water content, mechanical properties of optimized DN gels are comparable to those of industrial rubber. Tough DN gels consist of the two networks with completely different nature ; the first network is rigid, brittle and densely cross-linked polyelectrolyte gels and the second network is soft, ductile and sparsely cross-linked polyneutral gels. Such contrasting network structure induces large amount of "internal fracture" of the first network during deformation, which dissipates much energy and makes DN gels tough.
Today, I introduce some recent progress in DN gel studies. The first topic is molecular stent method, which enable us to synthesize DN gels from any chemical species. The second topic is internal fractrue analysis. The detailed fracture process of DN gels was carefully analyzed with several methods such as cycle tensile test and re-swelling measurement.