Blending Technology Accelerates

Aug. 29, 2011
External electrical fields promise to speed separation process a thousand-fold.

New composite materials are among a raft of innovations believed possible after a breakthrough in blending technology made by researchers at the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS), Warsaw.

Researchers studied how an external electric field affects the rate of component separation in blends composed of polymers and liquid crystals, and those composed of various types of polymers.

Inhomogeneous blends of polymers with other polymers or liquid crystals are widely used in industrial applications such as LCD displays and gas-flow sensors. The Warsaw researchers analyzed the behavior of such blends in alternating external electric fields.

"We managed to determine precisely the conditions permitting even a thousand-fold acceleration of component separation process in the blends under study," says professor Robert Hołyst, IPC PAS director for scientific affairs.

With time, many blends separate on their own into their components, usually at a very slow rate. It has long been known that the separation can be accelerated when an inhomogeneous liquid is placed in an external alternating electric field with an adequately tuned frequency. It is generally accepted that the acceleration of separation is due to ions in the mixtures.

In the presence of an alternating electric field with the strength of several million volts per meter, the ions of the component with higher conductivity start to move freely towards the electrode with the opposite charge. Having reached the phase interface with a non-conductive material on the other side, they are strongly hampered.

"Under these conditions, an additional force appears at the interface. With an electric field alternating at an appropriate frequency the ions start to yank the interface. Due to the yanking, the droplets of a component merge with each other significantly more efficiently than in the normal case, thus leading to a faster separation of both phases," says Natalia Ziębacz, a PhD student at the IPC PAS.

The separation efficiency of blends into their components strongly depends on the frequency of the applied electric field. Optical measurements carried out at the IPC PAS have shown that under optimal conditions, at frequencies up to the kilohertz range, the separation process is accelerated a thousand-fold.

The physical mechanism of this phenomenon suggests that similar effects can be expected in all blends containing ions, or components with different charge conductivities.

According to the researchers, being able to control the rate of separation opens the door to many interesting applications. For example, the separation process can be carried out very quickly and then stopped at any chosen stage. This would allow different blends of polymers and liquid crystals to be isolated and used in the development of new materials such as composites.

A patent application for the method has been filed.

In another development, the IPC PAS has been awarded a €3.3 million ($4.7 million) Noblesse grant from the European Union (EU) under the "research potential" section of its R&D budget. It's one of the largest awards ever made to a Polish research institution and forms part of the €7 billion ($10 billion) released by Research, Innovation and Science Commissioner Máire Geoghegan-Quinn in July. This money is aimed at equipping Europe to take on fierce global competition from emerging markets by tackling what the EU describes as its innovation deficit.

"The Noblesse grant will allow us to undertake activities that will further improve the quality of the scientific research conducted at our institute," says Hołyst. This will include employing a number of researchers from foreign research centers, organizing a range of international scientific conferences, and purchasing a high-quality electron microscope.

The grant will also be used to set up a number of new research groups dedicated to investigating topics such as quantum nanostructures, biospectroscopy, biosensors and green nanotechnology.

In addition, the funding will help the IPC PAS's own technological section called Chemipan. This develops and commercially manufactures fine and specialty chemicals and specialized products for agriculture and pharmacy — including pheromones and new drugs.

Seán Ottewell is Chemical Processing's Editor at Large. You can e-mail him at [email protected].