Polymeric nanomaterials can detect harmful substances in extreme environments

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Polymers have gained prominence in applications such as wearable electronics due to their flexibility and lightweight, but their low electrical conductivity has been a major drawback.

While various research efforts have been made to improve conductivity, there are still technical limitations, such as the need to use harmful solvents and performance degradation in extreme environments.

The Korea Institute of Science and Technology (KIST) has developed a method for synthesizing polymers based on ion-electron mixed conductors through collaborative research with Dr. Jang Ji-soo of KIST's Center for Electronic Materials Research and Professor Mingjiang Zhong of Yale University in the United States.

The study is published in the journal Advanced Functional Materials.

The research overcomes the limitations of existing polymeric conductors and is attracting attention as an innovative technology that can contribute to the development of next-generation high-performance chemical sensors.

The researchers introduced ionic pendant groups into the polymer structure to synthesize conjugated polymers that can easily dissolve in eco-friendly solvents rather than toxic solvents. In particular, the polymers exhibit high gas sensing performance in eco-friendly processes and can maintain stable performance in high temperature and humidity environments.

This technological advance opens up the possibility of applications in wearable devices, portable electronics, and other electronic devices that can operate reliably in extreme environments.

At the center of this research is the development of an ionization-based conjugated polymer that is soluble in an environmentally friendly solvent (2-methylanisole). While conventional conductive polymers typically require toxic solvents to dissolve, the new polymer significantly improves electrical conductivity through the binding of ionic species and electronic charge carriers.

By introducing anions (TFSI^-) and cations (IM⁺) into the polymer to increase the density and mobility of the charge carriers, the team maximized conductivity and stability.

The n-type based conductive polymer developed by the researchers, N-PBTBDTT, showed a very high sensitivity in detecting harmful gases such as nitrogen dioxide (NO₂). The sensitivity for NO₂ detection was as high as 189%, and it showed high detection ability even at a very low concentration of 2 ppb.

This performance exceeds that of conventional sensor technologies, and the polymer was also highly durable in environments with high humidity of 80% and high temperatures of up to 200°C. This enables stable gas detection in a variety of extreme environments, and is expected to be widely applied to wearable devices and industrial sensors.

"The sensors developed in this research go beyond simple chemical sensors and can bring about revolutionary changes in various applications," said Dr. Jang Ji-soo of KIST.

"In particular, it can be used as a life-saving material for those who work in extreme environments, such as firefighters who need to detect harmful gases at fire scenes and soldiers who are exposed to chemical weapons in wartime," said Prof. Junwoo Lee and Dr. Juncheol Shin, both first authors of the study.

More information: Junwoo Lee et al, Covalently Merging Ionic Liquids and Conjugated Polymers: A Molecular Design Strategy for Green Solvent‐Processable Mixed Ion–Electron Conductors Toward High‐Performing Chemical Sensors, Advanced Functional Materials (2024). DOI: 10.1002/adfm.202408146

Journal information: Advanced Functional Materials

Provided by National Research Council of Science and Technology