posted on 2021-08-21, 13:13authored byYuchen Mao, Yuto Kubota, Jin Gong, Takashi Kurose, Akira Ishigami, Kota Seshimo, Takuma Watabe, Daisuke Aoki, Hideyuki Otsuka, Hiroshi Ito
Stimuli-recovery
polymer networks with enhanced mechanical performance
were designed and synthesized through UV-curing photo-polymerization.
Thanks to a mechanochromic cross-linker difluorenylsuccinonitrile-containing
dimethacrylate (DFMA), poly(stearyl methacrylate-co-N,N-dimethyl acrylamide) (P(SMA–DMAA))
networks visualized the stress, showing improvements in toughness
and higher energy dissipation. The molar ratios determined the transition
temperatures, crystal structures, and mechanical performance of the
polymer networks. A more efficient and scientific analysis based on
achromatic gray-scale colorspace was first proposed to evaluate the
mechano-responsive color quantitatively. Uniform evaluation criteria
were expected to be established based on the method. The stress distribution
and dissociation of dynamic covalent bonds were recorded precisely
and expressed clearly on gray-scale color maps, providing a clear
warning for when materials were threatening to break. Mechanochromic
P(SMA–DMAA) networks showed a prolonged recovery at room temperature.
While under heat stimulation, they presented excellent recovery ability
with 90% strength and 95% energy. Additionally, the mechano-responsive
color changes repeated, showing a similar changing trend to that in
the first cycle. The mechanochromic stimuli-recovery P(SMA–DMAA)
networks had enhanced mechanical performance and a reliable visual
fracture warning function.