New nematic liquid-crystal phase structure characterized

Aberdeen, Scotland--The vast majority of liquid-crystal (LC) displays in devices such as mobile phones, computers, and televisions use nematic LCs. Nematics are similar to conventional liquids except that the LC molecules are preferentially ordered in one direction. However, when electrical fields are applied, they can be switched to another direction and act as shutters which can either let light through, or not.

The discovery of another kind of nematic phase three years ago by researchers from Dublin, Ireland and Hull, England and later identified by a team led by researchers from Southampton, England was particularly exciting -- not least because the new nematic phase can be switched much faster than the conventional nematic phase raising the possibility of much more energy-efficient displays.

A large international research effort to understand the structure of the new nematic phase saw an interdisciplinary team of researchers assembled involving chemists at the Universities of Aberdeen and Hull, physicists at the Liquid Crystal Institute at Kent State University (Kent, OH), and electrical engineers at Trinity College in Dublin. The team has now reported the structure of the new phase in the latest issue of Nature Communications.

The team found that the molecules are arranged in a ‘twist-bend’ structure with a periodicity of about 8 nm. Transmission electron microscopy was crucial in identifying the new structure. The studies showed arch-like structures and periodic arrays, which are not observed for conventional nematics, but are typical for this new LC phase.

“Since the beginning of the 20th century, only three nematic phases have been identified. It’s tremendously exciting to be involved in the identification of the fourth," says professor Corrie Imrie, chair of chemistry at the University of Aberdeen. "This new twist-bend nematic phase not only has fascinating properties which provide a demanding test of our fundamental understanding of condensed systems, but also has very real application potential. These applications could be anything from really impressive fast switching display devices such as far improved color TV screens and could even have benefits for biological sensors.”