Next-generation flexible electronics, such as bendable displays and medical implants, will rely on semiconductor materials that are mechanically flexible. Accurate predictions of the temperature when embrittlement occurs, known as the glass transition temperature, is crucial to design conducting polymers that remain flexible at room temperature.
Previous work to predict the glass transition of polymers relied on complex, multi-parameter models but nevertheless led to poor accuracy. In addition, accurate experimental measurements of the glass transition of conjugated polymers are challenging. All polymers become brittle when cooled; however, some polymers, such as polystyrene used in Styrofoam cups, become brittle at temperatures higher than room temperature while other polymers, such as polyisoprene used in rubber bands, become brittle at much lower temperatures.
An improved method to predict the temperature when plastics change from supple to brittle was developed that could potentially accelerate future development of flexible electronics. The method measures glass transition temperatures by keeping track of the mechanical properties as embrittlement occurs, laying the foundation for understanding the relationship between the glass transition and structure. Follow-up studies then determined the glass transition for 32 different polymers by measuring mechanical properties as a function of temperature.
This advancement, coupled with data for various polymers, revealed a simple relationship between the chemical structure and the glass transition, enabling researchers to predict the embrittlement point from the chemical structure of conducting polymers before they are synthesized for use in electronics. Most currently used conducting polymers are brittle and inflexible, so this advancement could accelerate the development of flexible electronics.
Next steps will be more extensive tests and exploration of practical applications, and designing conducting polymers to make stretchable electronics.