Professor Jae-Suk Lee's research team has succeeded in arranging conductive plastic molecules

□ Professor Jae-Suk Lee of the School of Materials Science and Engineering at the Gwangju Institute of Science and Engineering has (GIST • President Seung Hyeon Moon) has succeeded in controlling molecular alignment and thin-film manufacturing of conductive plastic materials.

□ Plastics applied to various advanced devices are required to have high functionality, such as electrical conductivity, energy storage, and optical characteristics, in addition to the properties of being flexible, wearable, and printable. However, unlike metal and ceramics, plastics have an irregular structure due to the entanglement of linear polymer chains within the macromolecules of the structure that can cause defects when applied to various devices.

∘ Recently, many research institutes have been studying plastic materials that have regular structure like metal and ceramics. However, in the thin film process for fabricating devices, regular alignment of the polymer chain structure becomes entangled like a thread. Controlling the plastic crystal structure is very difficult. Therefore, further studies on the plastic crystal structure is needed.

□ Professor Jae-Suk Lee succeeded in manufacturing a plastic film aligned on molecular scale * by inducing crosslinking between conductive polymers * and metal ion through a solvent-vapor thermal annealing process. This is expected to contribute to accelerating the practical use of plastic-based materials for energy and optical devices.

* Conducting polymer: An electrically conductive polymer (plastic). Conductive polymers, which are lighter, more flexible and easier to manufacture and process than other materials, are emerging as the next generation electronic materials.

* Molecular scale: less than a nanometer (or one billionth of a meter)

∘ Professor Jae-Suk Lee's research team has developed a method for manufacturing a plastic-based molecular crystal thin film by introducing zinc (Zn) metal ions into a conductive plastic material known as polyaniline *. A research team at the Korea Basic Science Research Institute analyzed the ordered plastic crystal structure.

* Ultra-high voltage electron microscope: an electron microscope capable of discriminating the atomic or molecule arrangement (0.12 nm) in a crystal by using an electron beam having an acceleration voltage of 1000 V or more

* In addition, a thin film of 100 nm thick was formed with a mixture of polyaniline * and zinc ion, followed by a simple solvent vapor heat treatment process to induce coordination between the nitrogen atom (N) and the zinc ion in the polyaniline structure. During the heat treatment of the solvent vapor, the zinc ion in the mixture thin film is positioned between the polyaniline polymer chains and forms a crosslinked structure by coordination bonding, thereby reducing the random motility of the polymer chain and inducing regular arrangement control.

* Polyaniline: A polymer having a repeating aniline structure by polymerizing an aniline material into which benzene is introduced (amine, NH2), which has many advantages such as easy processing and electrical conductivity.

∘ Precision ultrahigh-pressure electron microscopic imaging analysis of the polyaniline-zinc complex showed regularly arranged lattice structures on a molecular scale. It was also confirmed that the formed lattice has a face-centered cubic structure which is one of the major crystal structures of a metal. The electrical conductivity of the formed coordination complexes was increased more than 30 times compared to the control plastics (mixture of thin films).

□ Professor Jae-Suk Lee said, "Our research has established controls for producing conductive polymer through a simple process, and we have confirmed the regular arrangement of the structure at the molecular scale level. This development has the potential to be applied to future electronic, energy, and optical applications for devices.

□ Their research was published on April 21, 2017, in Nanoscale: "In situ formation of molecular-scale ordered polyaniline films by zinc coordination," which was authored by Hong-Joon Lee, Sang-Ook Hur, Min-Kyoon Ahn, Mohammad Changez, and Jae-Suk Lee with funding from the Basic Science Research Program though the National Research Foundation (NRF) funded by the Ministry of Science, ICT and Future Planning.