Study Opens the Door to Exploring New Force Regimes in Polymers

At theTokyo Institute of Technology, researchers have developed polymers infused with a stress-sensitive molecular unit that react to external forces by turning on their fluorescence.

The team has shown that the fluorescence depends on the magnitude of the force and demonstrated that it is feasible to detect both reversible and irreversible polymer deformations, thereby paving the way to finding new force regimes in polymers.

除了驱动物理运动外，机械力还可以负责引起调节和生产方法的化学变化，从而实现合适的材料特性。

One method to perform this is to introduce what is called a mechanophore into the material, molecular units that are sensitive to strain or stress. Particularly, mechanochromic mechanophores, which tend to change their optical properties in reaction to mechanical stimuli. They are extremely useful when it comes to measuring their local mechanical surrounding.

但是，大多数机械算术中的响应机制包括切断化学键。同时，需要激活巨大的机械力，并且它们的反应一般不可逆。

为了解决此类问题，由东京理工学院（Tokyo Tech）的Yoshimitsu Sagara教授指导的科学家早些时候设计了超分子机械粒子，这些机械粒子在荧光的关闭或关闭荧光下迅速逆转而不会造成任何共价债券。下一个困难是找出是否可以从同一分子基序中引起可逆和不可逆的机械回应。

In a new study published in the美国化学学会杂志, the researchers examine this question using a strange molecular architecture known as “rotaxane” in which a dumbbell-shaped molecule is threaded via a “ring” in such a way that they are interlocked mechanically, i.e. the “ring” cannot normally be pulled out.

研究人员说明了一种新型的机械响应，可以根据施加力的大小，可以是可逆的或不可逆的。他们通过将淬火器发射机对固定在轮济烷中并选择合适的环和塞子部分来实现这一目标。

When there is no force applied, the attractive interaction keeps the emitter-containing ring near the quencher fixed on the rotaxane's axle, so that the emission is quenched.施加弱力后，发射极从淬火器移开，并打开其荧光。这种效果是可逆的，除非力足够高以将戒指推到塞子上，以使不可逆的脱读发生.

Yoshimitsu Sagara, Professor, Tokyo Institute of Technology

A meticulously designed set of different rotaxanes was analyzed by the researchers and it was shown that a mixture of the suitably chosen ring and stopper moieties with the correct size is critical to achieving interlocked structures that exhibit such dual response.

Scientists from Tokyo Tech joined hands with Swiss partners from the University of Fribourg’s Adolphe Merkle Institute to integrate the new mechanophores into elastic polyurethane rubbers.

由于穿梭功亚博网站下载能，这种材料倾向于在几个拉伸释放周期中显示出可逆的荧光变化。另一方面，当橡皮筋反复发生变形时，由于轴上的环读引起的高应变时，会注意到永久性变化。

这种机制至少从概念上允许一个人监测聚合物材料的实际变形并检查过去根据光学信号造成的机械损伤亚博网站下载.

Yoshimitsu Sagara, Professor, Tokyo Institute of Technology

萨加拉（Sagara）推测了他们的研究结果的可能后果。

Extending the current library of mechanophores with our rotaxane-based candidates would be useful for studying the mechanical properties of not only polymers but also cells and tissues, as our mechanophores can respond to much smaller forces compared to those involving chemical bond scission.

Yoshimitsu Sagara, Professor, Tokyo Institute of Technology

Journal Reference:

Muramatsu，T。，等. (2021) Rotaxane-Based Dual Function Mechanophores Exhibiting Reversible and Irreversible Responses.美国化学学会杂志.doi.org/10.1021/jacs.1c03790.

来源：https://www.titech.ac.jp/english