Electronic displays could benefit from new class of liquid crystals
By Ben Coxworth
October 9, 2010
After five years of effort, chemists at Nashville’s Vanderbilt University have developed a new class of liquid crystals with an electric dipole that’s over twice that of existing liquid crystals... that’s good, right? Yes, it is. An electric dipole consists of two equal yet opposing electrical charges (i.e: positive and negative) within a molecule, that are physically separated from one another. The greater the distance between them, the larger the dipole. In liquid crystals, larger dipoles result in the ability to switch between bright and dark states faster, and lower threshold voltages – this means it requires less voltage to get them moving.
In products such as televisions and laptops, needless to say, faster, more energy-efficient liquid crystals would result in improved performance. If approved for commercial use, however, they would end up being blended with other types of liquid crystals to accentuate different optical, electrical, and other properties, depending on the device.
Even then, you might not be seeing them in your TV screen just yet. “Our liquid crystals have basic properties that make them suitable for practical applications, but they must be tested for durability, lifetime and similar characteristics before they can be used in commercial products,” said Vanderbilt professor of chemistry Piotr Kaszynski.
Besides their commercial applications, the new liquid crystals also have scientific significance. They have a “zwitterionic” (yes, seriously) structure, meaning that each molecule contains positively and negatively charged groups, yet have a net charge of zero. This means they’re electronically neutral. In these crystals’ particular case, the positively charged region is organic, while the negatively charged region is inorganic.
This unique structure allowed Kaszynski and grad student Bryan Ringstrand to create pairs of liquid crystals that had the same geometry, but different dipoles. To their surprise, subtle differences in structural geometry had a marked effect on the temperature at which they became liquid – more so than the strength of the dipole, which had previously been assumed to have the greatest effect.
The research was recently published in the Journal of Materials Chemistry.