Plasma polymerization approach incorporates TEMPO organic radicals into thin film coatings

The uniquely stable organic radical TEMPO, also called 2,2,6,6-tetramethylpiperidin-1-yl)oxyl, has shown promise for a wide array of applications ranging from energy storage to biomedical applications. Its radical nature, however, can make it challenging to incorporate into coatings via traditional wet-chemistry techniques.

Michl et al. have used plasma polymerization to incorporate TEMPO into thin film coatings in such a way that it retains its unique radical properties. By using plasma mass spectrometry, time of flight secondary ion mass spectrometry and high-performance liquid chromatography mass spectrometry alongside electron spin resonance, the group was able to track the fate of TEMPO molecules through the plasma phase into the coatings.

The group’s findings show that TEMPO can be reliably used in different plasma reactors to generate functional thin-film coatings, provided one adheres to higher process pressures and lower powers during deposition.

Thanks to how readily available TEMPO is, the group’s approach offers a potential path forward for its large-scale use in thin-film coatings without the need for wet-chemistry.

“If you want to coat an object, one approach would be to dip it into a bucket of paint, but that is rather wasteful and needs a lot of solvents,” said author Thomas Michl. “In contrast, we ‘zap’ it with our cold plasma, which deposits a coating without using any solvents and the need to dry.”

In addition to their non-medical uses, such as color-changing windows, catalysts and electrodes for batteries, the group works on coating wound dressings with these novel TEMPO coatings. They simulatenously reduce inflammation and infection, upgrading wound dressings into proactive actors in treating chronic wounds.

Source: “To be a radical or not to be one? The fate of the stable nitroxide radical TEMPO [(2,2,6,6-tetramethylpiperidin-1-yl)oxyl] undergoing plasma polymerization into thin-film coatings,” by Thomas Danny Michl, Dung Thuy Thi Tran, Kilian Böttle, Hannah Frederike Kuckling, Aigerim Zhalgasbaikyzy, Barbora Ivanovská, Alex Cavallaro, Maria Antonia Araque Toledo, Patrick James Sherman, Sameer A. Al-Bataineh, and Krasimir Vasilev, Biointerphases (2020). The article can be accessed at https://doi.org/10.1116/6.0000259 .