Polystyrene (shown) mixed with rubber has electrical properties.
Polymeric materials can exhibit 10 times more piezoelectric activity than crystals and ceramics, which are the strongest known piezoelectric materials. This “fundamentally new perspective in polymer science” could revolutionize electro-active devices such as sensors, energy storage devices, and biomedical devices, according to a statement from researchers at Oak Ridge National Laboratory (ORNL) and Technical University Aachen in Germany.
Piezoelectricity is the charge that builds up in materials such as ceramics when mechanical stress is applied. It can also work in reverse. While working with polymers, the researchers noticed the reverse piezoelectric effect, which is defined as creating a mechanical strain by applying an electrical voltage.
“We observed this effect when two different polymer molecules like polystyrene and rubber are coupled as two blocks in a di-block copolymer,” said Volker Urban, a researcher at ORNL in a statement.
The observations made the researchers curious because non-polar polymers were not thought to be capable of demonstrating any kind of piezoelectric effect. The researchers give more details about further experiments:
Temperature-dependent studies of the molecular structure revealed an intricate balance of the repulsion between the unlike blocks and an elastic restoring force found in rubber. The electric field adds a third force that can shift the intricate balance, leading to the piezoelectric effect.
Source: “ORNL Discovers Amazing Electrical Properties in Polymers,” ORNL press release, 9/23/11
Image by gatl (Alexandre Duret-Lutz), used under its Creative Commons license.
Rachel Petkewich is a freelance science writer and editor. She has worked as a research scientist in the chemical industry and spent eight years as a staff writer and editor at various science journals and magazines, including Chemical & Engineering News.
