Dec 12 2019
北海道大学的研究人员开发了一种水凝胶，与通常这样做的聚合物基材料（如塑料瓶）相反。亚博网站下载冷却后加热并变软时，它们的材料会变硬。他们的发现可能导致制造防护服装，以实现交通和与运动有关的事故。
热稳定蛋白的灵感
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.
新开发的廉价的聚丙烯凝胶
该团队基于这个概念开发了一种廉价的，无毒的聚丙烯凝胶。由聚电解质（丙烯酸）（PAAC）组成的凝胶浸入乙酸钙水溶液中。PAAC自身的作用就像其他基于聚合物的材料一样，加热时会变软。但是，当添加乙酸钙时，PAAC的侧面残基与乙酸钙分子相互作用，类似于嗜热蛋白质内发生的方式，导致PAAC的作用差异很大。
聚合物致密和稀疏相
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 ionic bonds and hydrophobic interactions between polymer molecules. This causes the material to rapidly transform from a soft, transparent hydrogel to a rigid, opaque plastic.
僵硬，更坚固，更坚硬的水凝胶
The heated material was 1,800 times stiffer, 80 times stronger, and 20 times tougher than the original hydrogel. The soft-to-rigid switching was completely reversible by alternatively heating and cooling the material. Moreover, the scientists could fine-tune the switching temperature by adjusting the concentration of the ingredients.
“This polymer gel can be easily made from versatile, inexpensive and non-toxic raw materials that are commonly found in daily life. Specifically, the polyacrylic acids are used in disposable diapers and calcium acetates are used in food additives,” Jian Ping Gong added.
“Our study contributes to basic research on new temperature-responsive polymers, and to applied research on temperature-responsive smart materials。”
Possible Application in Protective Clothing
然后，他们通过将材料与编织玻璃织物结合使用来证明材料的应用。这种新的织物在室温下柔软，但是当将其在沥青表面上拉到五秒钟的速度80 km/小时时，摩擦产生的热量使材料硬化，仅在接触表面上形成少量擦伤。
Takayuki nonoyama说：“例如，用类似织物制成的衣服可以用来保护在交通或与运动有关的事故中保护人员。我们的材料也可以用作吸热窗涂层，以使室内环境更凉爽。”
Source:https://www.global.hokudai.ac.jp/