#Stable supply of electrochromic metallo-supramolecular polymer

National Institute for Materials Science (NIMS) and Tokyo Chemical Industry Co., Ltd. (TCI) have jointly developed a synthetic process capable of stably supplying a metallo-supramolecular polymer electrochromic (EC) material. Popularization of this material may stimulate growth in the market for dimming windows capable of electrically changing tint from transparent to dark.

Self-dimming EC windows can electrically change tint from clear to dark, allowing them to function as window blinds and curtains. Global research efforts have been made to put these next-generation window glasses into practical use with the expectation that they could be used to eliminate the need for window blinds and curtains in offices and living spaces. A dimming EC glass is composed of an EC material layer sandwiched between two glass sheets which have transparent electrodes attached. Its color changes when an electric current passes between the electrodes. Forming an EC material layer on large glass surfaces is currently very expensive as it requires the use of vacuum deposition equipment, hindering the widespread use of dimming EC windows by the public. In 2005, NIMS developed a metallo-supramolecular polymer EC material which can be deposited as a layer onto glass surfaces at lower cost. This material exhibits excellent chromogenic properties and color change response and can continue to display the color it has produced even after the current is removed, enabling it to operate energy efficiently. Development of a mass production compatible process for this material had been much anticipated.

In this research project, NIMS and TCI jointly developed a process to synthesize the metallo-supramolecular polymer EC material from organic molecules. This synthetic process is expected to allow stable mass production of high-quality EC materials. This system is currently capable of producing hundreds of grams of the material per month—a sufficient amount to form an EC material layer on several dozen square meters of glass surfaces. The research group has been attempting to increase the mass production capacity of the system in order to further promote commercial use of the material.