Reviewed by Danielle Ellis, B.Sc.Nov 26 2024
According to a study published in Advanced Functional Materials, the Korea Institute of Science and Technology (KIST) established a method for synthesizing polymers based on ion-electron mixed conductors in collaboration with Dr. Jang Ji-soo of KIST’s Center for Electronic Materials Research and Professor Mingjiang Zhong of Yale University in the United States.
KIST researchers utilize gas-sensitive materials that are stable in extreme environments. Image Credit: Korea Institute of Science and Technology
Due to their flexibility and low electrical conductivity, polymers have become more popular in applications like wearable electronics; nonetheless, this has proved to be a significant disadvantage. Despite numerous research attempts to increase conductivity, there are still technical obstacles, such as the requirement for hazardous solvents and performance degradation in harsh conditions.
The study addresses the constraints of conventional polymeric conductors and is gaining traction as a new technology that can help construct next-generation high-performance chemical sensors.
To address this issue, the researchers included ionic pendant groups into the polymer structure, resulting in conjugated polymers that can be easily dissolved in environmentally benign solvents rather than hazardous ones.
The polymers, in particular, show excellent gas sensing performance in environmentally friendly processes and can sustain stable performance in high temperature and humidity settings. This technological advancement allows wearable devices, portable electronics, and other devices to operate consistently in severe situations.
The main goal of this study is to create an ionization-based conjugated polymer that dissolves in 2-methylanisole, an eco-friendly solvent. By attaching ionic species and electronic charge carriers, the novel polymer significantly improves electrical conductivity, whereas conventional conductive polymers usually require harmful solvents to dissolve.
The researchers optimized conductivity and stability by adding cations (IM+) and anions (TFSI-) to the polymer to boost the density and mobility of the charge carriers.
The researchers’ n-type conductive polymer, N-PBTBDTT, demonstrated great sensitivity in detecting hazardous gasses such as nitrogen dioxide (NO2). The sensitivity for NO2 detection was as high as 189%, and it demonstrated good detection ability even at low concentrations of 2 ppb.
This performance outperforms that of current sensor technologies, and the polymer was also extremely robust in settings with 80% humidity and temperatures as high as 200°C. This allows for robust gas detection in a variety of harsh situations, and it is likely to be widely used in 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.
Dr. Jang Ji-soo, Senior Researcher & Assistant Professor, Korea Institute of Science and Technology
Prof. Junwoo Lee and Dr. Juncheol Shin, the study's first authors, added, “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.”
The Ministry of Science and ICT supported this study as part of KIST’s Institutional Program.
Journal Reference:
Lee, J. et. al. (2024) 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. doi.org/10.1002/adfm.202408146