Bio-inspired hydrogel can rapidly switch to rigid plastic

phys.org | 11/18/2019 | Staff
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Hokkaido University researchers have developed a hydrogel that does the opposite of what polymer-based materials, like plastic bottles, normally do: their material hardens when heated and softens when cooled. Their findings, published in the journal Advanced Materials, could lead to the fabrication of protective clothing items for traffic and sports-related accidents.

Takayuki Nonoyama and Jian Ping Gong of Hokkaido University and their colleagues were inspired by how proteins remain stable inside organisms that survive within extreme-heat environments, like hot springs and deep sea thermal vents. Normally, heat "denatures" proteins, altering their structure and breaking their bonds. But the proteins within thermophiles remain stable with heat thanks to enhanced electrostatic interactions such as ionic bonds.

Team - Polyacrylic - Gel - Concept - Gel

The team developed an inexpensive, non-toxic polyacrylic gel based on this concept. A gel composed of polyelectrolyte poly (acrylic acid) (PAAc) was immersed in a calcium acetate aqueous solution. PAAc on its own acts like any other polymer-based material and softens when heated. But when calcium acetate is added, PAAc's side residues interact with the calcium acetate molecules, in a way similar to what happens inside thermophile proteins, causing PAAc to act very differently.

The team found that their originally uniform gel separates into a polymer dense "phase" and a polymer sparse one as the temperature rises. When it reaches to a critical temperature, in this case around 60°C, the dense phase undergoes significant dehydration which strengthens...
(Excerpt) Read more at: phys.org
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