Electricity Changes Polymer’s Optical Properties

A newly developed polymer is said to be the first of its kind to combine optical and electrical properties. This could mean new manufacturing possibilities for glass, polarization filters and sensors capable of detecting single molecules of a given chemical.

An international team from the University of Milan, the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS), and the Leibniz Institute of Solid State and Materials Research has developed the new polymer, which can change its spatial configuration when electric potential is applied. This also gives it a chiral property and impacts the polarization of transmitted light.

Professor Wlodzimierz Kutner demonstrates two halves of a newly developed polymer that are connected at a single point and can be rotated with respect to each other by applying electric potential. Courtesy of the Institute of Physical Chemistry of the Polish Academy of Sciences.

"Until now, to give polymers chiral properties, chiral pendants were attached to the polymer backbone. In such designs the polymer was used as a scaffold only,” said Wlodzimierz Kutner, a professor at IPC PAS. “Our ... polymer is both a scaffold and an optically active chiral structure. The polymer conducts electricity.”

The polymer was based on thiophene, an organic compound composed of a five-member aromatic ring containing a sulfur atom. The basic component of the new polymer is made of a dimer with two halves, each made of two thiophene rings and one thianaphthene unit.

In the study, the halves were connected at a single point and partially rotated by applying electric potential. Depending on the orientation of the halves, the researchers said, the new polymer either assumes or loses chirality. Such behavior is fully reversible and resembles a breathing system, the researchers said.

The study of molecular imprinting by IPC PAS prompted development of the new polymer. It was used as a receptor in chemosensors capable of selective capturing of molecules of various analytes.

The new material could be used in polarization filters and window glass with continuously adjustable transparency, the researchers said. The polymer’s mechanical properties also make it suitable for use with chemical sensors for selective detection and determination of optically active and chiral forms of an analyte.

The research was published in Angewandte Chemie International Edition (doi: 10.1002/anie.201309585).