Most liquid-crystalline displays contain rod-like molecules that quickly switch from one orientation to another when subjected to electric fields. This movement creates a shutter effect that turns light on and off at high rates.
But the conductivity of rod-like molecules pales in comparison to disc-shaped, or discotic, liquid crystals. Composed primarily of aromatic molecules surrounded by flexible side chains, discotic molecules can stack into extended columns that enable one-dimensional charge transport and semiconducting capabilities. However, these columns have such tight packing that no one has found a way to orient them reliably using electricity.
Now, researchers led by Takuzo Aida from the University of Tokyo, Hideo Takezoe from the Tokyo Institute of Technology and Masaki Takata from the RIKEN SPring-8 Center in Harima have discovered that aromatic amides with branched, paraffin-like side chains can act as molecular ‘handles’ for electric field alignment1. Furthermore, they succeeded in growing discotic films hundreds of times thicker than before, putting devices that incorporate this technology one step closer to production.
Aida and colleagues were investigating discotic liquid crystals consisting of molecules called corannulene derivatives when they made their finding. Corannulene has a core of five fused hydrocarbon rings surrounded by ten aromatic amides, giving it a bowl-like shape. Despite this compound’s large size, the researchers found that electric fields could uniformly align the columns with hexagonal geometries over a range of temperatures (Fig. 1).
The researchers first postulated that the inner dipole of the curved corannulene core accounted for the field-induced orientations. But when they synthesized a similar discotic liquid crystal containing a flat, non-polar triphenylene core, they observed the same striking field alignment—key evidence that the amide side chains acted as responsive handles that interact with the applied electric field and guide the discotic molecules into place.
Armed with this knowledge, the researchers synthesized several discotic columnar liquid crystals with slightly tweaked handles to optimize this behavior. Nearly all of these entities showed columnar alignment that persisted even after extinguishing the electric field. The team could also break apart the columns and restore the molecules’ random orientations using a simple heating procedure.
Because the column heights depended on applied field strength, the researchers produced millimeter-thick films in any desired orientation by sandwiching their compounds between two large-area electrodes. “Unless conducting discotic columns can be aligned to macroscopic length scales, they will remain impractical,” says Aida. “Therefore, our achievement is quite important for organic electronic device applications.”Reference:
Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute
Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy