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Researchers at the University of Tsukuba have developed a novel method for controlling the optical rotation of conductive polymer polythiophene in a magnetic field at low voltage. This method combines the "Faraday rotation" phenomenon, in which a polarizing plane rotates in response to a magnetic field, with the electrochemical oxidation and reduction of conductive polymers.

The study is in the journal Molecular Crystals and Liquid Crystals.

Conductive polymers possess various properties in addition to conductivity, with applications in light-emitting devices, electromagnetic wave shielding, and anticorrosion materials.

One of their properties is the generation of polarons, which are virtual particles responsible for electrical conduction and are formed during doping via electrochemical oxidation in conductive polymers. These polarons considerably influence optical and magnetic properties.

Herein, researchers focused on the "Faraday rotation" phenomenon, in which optically inactive substances exhibit optical rotation when linearly polarized light passes parallel to a magnetic field.

The research group has previously synthesized various optically active conductive polymers in liquid crystals. Herein, the researchers synthesized optically inactive polythiophenes and modulated their polarons by electrochemically oxidizing and reducing (doping and dedoping) them in a magnetic field under a Faraday configuration at a constant low voltage of 1.5 V.

Thus, a combination of magnetic modulation and electrochemistry endows conducting polymers with electrochemical control of optical rotation. They developed a method for controlling the optical rotation of achiral polythiophenes. This method has promising applications in magnetic field sensors and optical communication devices.