New family of liquid crystals created

Oct 05, 2010 By David F. Salisbury
Liquid crystal films make beautiful patterns. This pattern is made by one of the new family of liquid crystals. They form one of the most common liquid crystal forms, called the nematic phase. The word nematic comes from a Greek word for thread because they contain thread-like defects. Credit: Kaszynski lab

(PhysOrg.com) -- Chemists at Vanderbilt University have created a new class of liquid crystals with unique electrical properties that could improve the performance of digital displays used on everything from digital watches to flat panel televisions.

The achievement, which is the result of more than five years of effort, is described by Professor of Chemistry Piotr Kaszynski and graduate student Bryan Ringstrand in a pair of articles published online on Sept. 24 and Sept. 28 in the Journal of Materials Chemistry.

"We have created liquid crystals with an unprecedented , more than twice that of existing liquid crystals," saysKaszynski.

Electric dipoles are created in molecules by the separation of positive and negative charges. The stronger the charges and the greater the distance between them, the larger the electric dipole they produce.

In liquid crystals, the electric dipole is associated with the : the minimum voltage at which the operates. Higher dipoles allow lower threshold voltages. In addition, the dipole is a key factor in how fast liquid crystals can switch between bright and dark states. At a given voltage, liquid crystals with higher dipoles switch faster than those with lower dipoles.

Commercial potential

Vanderbilt has applied for a patent on the new class of materials. Some of the companies that manufacture liquid crystals for commercial applications have expressed interest and are currently evaluating it.

"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," Kaszynski says.

If it passes commercial testing, the new class of liquid crystals will be added to the complex molecular mixtures that are used in liquid crystal displays. These blends combine different types of liquid crystals and other additives that are used to fine-tune their characteristics, including viscosity, temperature range, optical properties, and chemical stability. There are dozens of different designs for liquid crystal displays and each requires a slightly different blend.

Scientific significance

The newly discovered liquid crystals are not only important commercially but they are also important scientifically.

Since 1888 when they were discovered, scientists have discovered more than 100,000 natural and synthetic compounds that have a liquid crystal state. They have determined that one of the prerequisites for such a state is that the molecule must be shaped like either a rod or a disc. A second requirement is that it must contain both rigid and flexible parts. It takes a delicate balance of two opposing factors or forces to produce a material halfway between a crystal and a liquid. However, there is still a great deal about this unusual state that scientists do not yet understand.

For example, scientists are still trying to determine the effect that a liquid crystal's electric dipole has on the temperature at which it becomes an ordinary liquid. The current consensus has been that increasing the strength of the dipole typically raises this transition temperature. The way in which the new type of liquid crystals are synthesized allowed Kaszynski and Ringstrand to test this theory by creating pairs of liquid crystals with the same geometry but different electric dipoles and measuring their transition temperatures. They found that subtle structural differences have a much greater effect on the transition temperature than do variations in the strength of the electric dipole.

Unique "zwitterionic" structure

What distinguishes the new class of liquid crystals is its "zwitterionic" structure. Zwitterions are chemical compounds that have a total net electrical charge of zero but contain positively and negatively charged groups. The newly developed liquid crystals contain a zwitterion made up of a negatively charged inorganic portion and a positively charged organic portion. Kaszynski first got the idea of making zwitterionic liquid crystals nearly 17 years ago when he first arrived at Vanderbilt. However, a critical piece of chemistry required to do so was missing. It wasn't until 2002 when German chemists discovered the chemical procedure that made it possible for the Vanderbilt researchers to succeed in this effort.

Explore further: New, more versatile version of Geckskin: Gecko-like adhesives now useful for real world surfaces

Related Stories

When liquid crystals with a metal center are 'shaking hands'

Mar 14, 2005

Without liquid crystals (LC's) our cell phones and notebook computers would not be possible, for these compounds keep our display screens flat and lightweight. Being a phase of matter whose order is intermediate between that ...

Recommended for you

A greener source of polyester—cork trees

Apr 16, 2014

On the scale of earth-friendly materials, you'd be hard pressed to find two that are farther apart than polyester (not at all) and cork (very). In an unexpected twist, however, scientists are figuring out ...

User comments : 0

More news stories

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...