American chemists have obtained cyclic polymers, the instantaneous decomposition of which can be triggered by a precise signal.
Commissioned by the US Department of Defense, chemists have worked on the creation of electronic sensors and their delivery vehicles that do not leave traces after use. However, the project turned out to be an even more impressive find - a material suitable for making small drones or parachute cloth that will self-destruct upon completion of the mission. Paul Kohl and his colleagues from the Georgia Institute of Technology spoke about this at the fall meeting of the American Chemical Society in California.
Each polymer has its own limiting temperature, above which it tends to decompose into monomer units. In the household polymers we are used to, it is quite high and is not achieved under normal conditions, and depolymerization does not develop too quickly. Therefore, the authors of the new work turned to cyclic polymers, which have a low limiting temperature. In addition, when only one covalent bond is destroyed, their links quickly disintegrate. It is enough to use a photosensitive catalyst, which will start the process of rapid degradation.
© Georgia Institute of Technology
Work on such materials has been going on for a long time, but until now the resulting polymers remained unstable even at room temperature. Paul Kohl and his team were able to find more stable polymers and improve their synthesis. “This material is not one that decays slowly over the years, like ordinary biodegradable plastic,” the scientist said. "The polymer disappears instantly as soon as you trigger the internal degradation mechanism or as soon as the sun's rays hit it."
Wet spot (right) is all that remains of a self-decomposing polymer sample exposed to light / © Georgia Institute of Technology
Using various photocatalysts to trigger the decomposition, the authors were able to control this process by “turning it on” in response to a particular radiation wavelength. In particular, by making the polymer react to ultraviolet light, they were able to work with the material in the room, however, as soon as it was exposed to sunlight, it quickly decomposed. Using various copolymers, chemists have also been able to slow down the degradation by delaying it for a few hours that may be needed to complete the mission. They managed to get a miniature glider drone, as well as a piece of parachute fabric from such materials.