Russian researchers have developed a simple technique for raw material preparation in order to produce electrically conducting polymers. These polymers are an essential part of flexible displays, another technological breakthrough.

Scientists from Novosibirsk (the Institute of Solid Body Chemistry and Mechanical Chemistry of Siberian branch of Russian academy of sciences) have found out that adding saturated aquatic solution of urea to alcohol promoted alcohol molecules to form fibers. When heated, mentioned mixture can turn into an organic semiconductor, called polyacetylene.

Electrically conducting polymers are of interest to researchers because of a number of unique properties. These polymers, unlike standard conductors and semiconductors, combine ability to conduct electric current with standard mechanical properties of plastic materials. Moreover, production of electrically conducting polymers is often reasonably cheap. A good example of promising applications of electrically conducting polymers is making flexible displays.

In standard state molecules of a polymer look like a ball of threads, tangled by a cat, and are not very good at conducting electricity. In order to make electron transfer between polymer molecules much more effective, one has to promote formation of intermolecular aggregates from straightened polymer chains. A Russian think-tank suggests using a common and cheap chemical compound – urea or carbamide or carbonic acid diamide – for this purpose.

 

 

Scientists mixed a saturated aqueous solution of urea with 10%-solution of polyvinyl alcohol (PVA) and let the mixture stand at room temperature for several days – not a complicated technological process at all. After incubation the solution was full of fibers, some of which were one centimeter long.

The effect urea had on formation of ordered structures from polyvinyl alcohol was studied by means of transmission electron microscopy. A net was put in a solution with low polyvinyl alcohol content, and then it was used as a substrate for a polymer material. Later on urea molecules were removed from a sample surface, and a net, covered with polyvinyl alcohol, was transferred to a transmission electron microscope chamber. Images, taken by means of the microscope, clearly demonstrate distinctive bands, indicating presence of filamentous formations.

Interactions between urea molecules and polyvinyl alcohol molecules were also confirmed by means of infrared spectroscopy and Raman scattering spectroscopy, which indicates that the process really happens. Urea molecules, when added to polyvinyl alcohol solution, apparently enable formation of specific filamentous aggregates and fill gaps between these aggregates as well. According to the Russian researchers, this filamentous material can be dried and used for synthesizing fibers of an organic semiconducting material – polyacetylene.

You can read more on the subject in the recent paper of the Russian chemists, published in the Russian-language science journal “Solid body physics”.