Create new materials that 'vanish' as ​​soon as they're exposed to the sun

A photosensitive additive added by US military researchers to polymers has created the material that dissolves into water and evaporates upon exposure to sunlight. This new material will be applied in military, science and construction.

The success of the study was presented by the Georgia Institute of Technology at the 2019 American Chemical Society (ACS) Fall 2019 Exhibition and Convention in San Diego on June 26.

Researchers at the Georgia Institute of Technology say the new biodegradable material, unlike biodegradable plastic materials that takes years to decompose as usual, will immediately disappear when activated. or exposure to the sun.

The key to making a biodegradable polymer is "ceiling temperature". Under the ceiling temperature, the molecular configuration of the polymer is firmly connected, but above that temperature they will be separated. Conventional polymers, such as polystyrene thermoplastics, usually have a ceiling temperature above ambient temperature and are very stable. Even if they are warmed above ceiling temperature, some of these materials still take a long time to decompose.

Before and after the new material is exposed to sunlight - (Image: Paul Kohl)

In the new material, the polymer has a low ceiling temperature, so only one molecule bond is broken, all the other bonds are also separated. Therefore, the process of reducing polymers occurs quickly.

To create this material, the researchers integrated into the polymer a photosensitive additive, which helps absorb light and speed up the process of reducing polymers. In room fluorescent conditions, the material remains stable, but when exposed to sunlight, it evaporates. In some cases, they melt into liquid.

"We have discovered a number of compounds that can optimize the process of reducing polymers at different wavelengths of light, so we have created objects , " said Dr. Paul Kohl, member of the research team. "They are designed for applications where you enter the room and turn on the lights and everything will disappear immediately."

Besides, Kohl's team also found a way to postpone the process of reducing polymers. This process lasts about 2-3 hours after being exposed to sunlight.

Dr Kohl said the research was conducted by the US Department of Defense, so it will be used to build military equipment in the immediate future. For now, researchers continue to experiment with adding different compounds that can be added to phthalaldehyde to change the properties of the material while preserving its self-destructive properties.

In the future, this material will be applied to create a biodegradable epoxy, a temporary adhesive that can be used in construction materials. This material can be used in environmental sensor design or space science equipment. When the sensor is finished collecting data will be activated to self-evaporate without leaving environmental waste.

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