Novel Electro-optic and Photonic Behaviours in Bent Core Liquid Crystals

Lead Research Organisation: University of Manchester
Department Name: Physics and Astronomy


Liquid crystals are self-organizing fluids that display a remarkable array of structures, each of which has subtly different physical properties. They are best known for their use in liquid crystal devices (LCD), a hugely successful technology in which cigar-shaped molecules are organized so that on average their long-axes point along a direction that can be controlled by an electric field. The ordered structure they form is birefringent, so interacts with polarized light, and LCDs result when the birefringence, and hence transmission of polarized light, is modulated by a voltage. Control of the molecular shape and structure can result in the formation of different liquid crystal phases and offer a route to control many desirable properties.

In this proposal, we aim to exploit some very new research in which the molecular structure has a bent-core, leading to a new class of nematic liquid crystals with properties that can include ferroelectricity, biaxiality, enhanced flexoelectricty, unusual visco-elastic behaviour and therefore new electro-optic effects. We propose to produce such materials that are room-temperature and to generate a detailed understanding of their physical properties. We expect that this will lead us to new kinds of fast switching that could either be used in displays or indeed in other kinds of electro-optic devices. For example, we expect that some of these materials will exhibit optical nonlinearity - this means that when red light is shone into them, blue light emerges (this is known as frequency doubling), and such materials find uses in photonic devices such as lasers.

The research period is a short one as we wish to make rapid use of our existing expertise in a subject area that is changing rapidly. We believe that we can carry out sufficient research in a year, using fully trained personnel in an environment where we have all of the necessary experimental methods at our fingertips, to understand which areas need further research, and which can lead immediately to technology that is ripe for transfer to our industrial colleagues via 'follow on' or other knowledge exchange mechanisms. Therefore, we expect this research programme to be very cost-effective, delivering several high-quality papers on the fundamentals of these systems, and also to lead to high impact as we transfer some of the most interesting technology to our industrial colleagues.

Planned Impact

The non-academic impact of the research in this proposal are as follows.

1. Economic. There is potential for the production of new materials that fall into two categories. Firstly, they may be useful in new liquid crystal displays and switching modes as the materials have potential in engineering elastic and flexoelectric liquid crystal properties and to contribute to display modes via polar smectics, polar and/or biaxial nematics and Kerr effect in blue phases. The materials are expected to also exhibit useful optical and electro-optical properties that may be relevant to optical switches (Kerr effect, nonlinear optical properties), sensors (high birefringence, ferroelectric properties) and possible healthcare technologies (high birefringence materials would be relevant to an ongoing project on producing switchable contact lenses for presbyopia).

2. People. We will train scientists at undergraduate, postgraduate and postdoctoral level in an interdisciplinary environment, who are highly employable both by UK industry and academia.

3. Public engagement. The research topic is extremely visual and relevant to a significant amount of everyday technology. We will therefore take full advantage of communicating the excitement of contributing to new devices and display concepts in our public engagement activities. The potential of using these new materials in areas as diverse as switchable contact lenses, or indeed in helping us to understand aspects of biological function (we showed how some animals can see polarized light by using our techniques for understanding and designing optical devices in liquid crystals!) helps us to inspire the next generation of young scientists and explain to the public how the research they help to fund can end up being useful.


10 25 50
Description 1. A new kind of optical switch in which the refractive index changes dramatically in response to an applied voltage. This could be useful in many kinds of display and non-display devices and we've reported the potential for switchable lenses.
2. We have discovered a new kind of organisation in mixtures of liquid crystals that include a bent-core molecule. We are currently understanding this structure and will see some time in the future whether this has applications.
3. We have developed a detailed understanding of flexoelectricity in bent-core materials. This will have relevance to researchers considering the use of the flexoelectric effect in devices that may be electro-optic or energy harvesting.
4. We have discovered that the conformational fluctuations in the molecules can be amplified in the liquid crystal systems. In particular, we find that fluctuations in the chiral conformers has an unexpectedly large impact on the energy cost of the twist deformation in liquid crystals.
5. Several PhD awards have been made using materials and understanding developed during this project.
6. Two early career researchers won the 'Young Scientist Prize' of the British Liquid Crystal Society, with work that was part of this project, or very closely related to it, forming a significant part of their portfolio.
7. The researchers involved in the project played significant roles in conferences disseminating results. In one case, the early career researchers were on the organising committee and led a public engagement event.
8. The PhD students whose work was based on this project also took part in outreach, including Pint of Science in Leeds.
Exploitation Route The new electro-optic effect could be of significant interest to new kinds of photonic devices.
The amplification of chirality could be of interest at very fundamental levels - and offers a new way to tune the twist elastic constant in liquid crystal mixtures.
The significant involvement of early career researchers in outreach events is important training that will allow them to continue to inspire schoolchildren and the general public about the applications of novel soft materials.
Sectors Chemicals,Education,Electronics,Energy,Healthcare

Description A new electro-optic effect discovered in the dark conglomerate phase has been reported and suggested for use in switchable photonics devices including lenses. New structures in mixtures were found to form a doubly-nematic gel in which two levels of hierarchical self assembly resulted in a new kind of gel structure. A better understanding of flexoelectricity in bent-core liquid crystals was being developed, of potential relevance to electro optic and energy harvesting devices. Finally, a new understanding of chiral amplification was developed, demonstrating the important role that chiral conformers play in the overall properties of achiral materials.
First Year Of Impact 2014
Sector Electronics