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Polymers tout 10x higher piezoelectric effect

Posted: 30 Sep 2011 ?? ?Print Version ?Bookmark and Share

Keywords:copolymer? piezoelectric? electro-active device?

Researchers at Oak Ridge National Laboratory (ORNL) have discovered a material that has 10 times the piezoelectric effect of crystals and ceramics. Until now, scientists are wary that non-polar polymers can demonstrate any piezoelectric effect, which is a property of non-conductive materials.

ORNL's Volker Urban and colleagues at the Technical University Aachen in Germany noticed the reverse piezoelectric effectdefined as creating a mechanical strain by applying an electrical voltagewhile conducting fundamental research on polymers. At first, observations were not taken in terms of classic piezoelectric materials.

"We thought about comparing the effects that we observed to more 'classic' piezoelectric materials and were surprised by how large the effects were by comparison," stated Urban, researcher at ORNL. "We observed this effect when two different polymer molecules like polystirene and rubber are coupled as two blocks in a di-block copolymer."

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.

"The extraordinarily large response could revolutionize the field of electro-active devices," said Urban, who listed a number of examples, including sensors, actuators, energy storage devices, power sources and biomedical devices. Urban also noted that additional potential uses are likely as word of this discovery gets out and additional research is conducted.

"Ultimately, we're not sure where this finding will take us, but at the very least it provides a fundamentally new perspective in polymer science," Urban added.

The paper titled "Piezoelectric Properties of Non-Polar Block Copolymers," included Markus Ruppel and Jimmy Mays of ORNL and Kristin Schmidt of the University of California at Santa Barbara. Authors from Aachen University are Christian Pester, Heiko Schoberth, Clemens Liedel, Patrick van Rijn, Kerstin Schindler, Stephanie Hiltl, Thomas Czubak and Alexander B?ker.

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