Stretching the boundaries; new soft matter systems.

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Imagine materials that allow better protection against impact because they push back when hit, rather than getting thinner. Or optical materials that could make the next generation virtual and augmented reality vision devices energy efficient and fast enough to produce real-time holograms. Or new, non-toxic materials for that convert heat energy to electricity, and flow so provide the heat-exchanging medium. Such materials have come into existence in the last 5 years, and this proposal is designed to take them from early stage discovery, building a deep and comprehensive understanding of the physics, towards new applications. The proposal is founded on two of my discoveries in liquid crystals; the first synthetic auxetic material (a liquid crystal elastomer), and a novel electro-optic response in a rather esoteric liquid crystal state, the dark conglomerate phase. It also builds on my exploratory work of the electrocaloric effect in well-known ferroelectric LCs positioning me to examine the potential of newly discovered polar nematics. 1. Auxetic LC elastomers. Imagine a material that gets thicker when you stretch it rather than thinner! Such materials are known as auxetic and exist in nature in tendons, nacre, the cell nucleus and even cat skin. Auxetic materials are predicted to have extremely desirable properties including: high shock absorbance; tear resistance; high shear moduli; and to be acoustic meta-materials. Most existing synthetic auxetic materials involve porous geometries with typical dimensions of >10micrometres, limiting the possible device dimensions and introducing inherent weakness (it is easy to tear a sponge). I recently discovered the first synthetic molecular auxetic material offering a paradigm shift in developing materials for applications spaning automotive, aerospace, electronics and healthcare industries. My aim is to develop a deep understanding of the physics underpinning the phenomenon and engage academic and industrial collaborators.2. Optically isotropic electro-optic modes. Liquid crystals have been a potential solution for switchable optics (and optical switches) for decades, but are inefficient and too slow for next generation devices. The dark conglomerate (DC) phase shows a remarkable electro-optic response, a large change in refractive index which is both fast and polarization-independent that could completely change the way in which switchable lenses and gratings could be designed. I plan to build on my work on the DC phase, understanding materials and mixtures that exhibit the phase, to take it from a scientific curiosity to one where the potential for new electro-optic devices is fully understood. 3. Polar nematic LCs for energy. This strand combines a recent discovery at York with my exploratory research into liquid crystals as electrocaloric materials. Electrocaloric materials convert heat into electricity (and vice versa) and having a fluid material that does this offers a new approach to device design. Unfortunately, fluid materials tend to have an electrical polarization that is orders of magnitude too small to be effective. The polarization in the splay nematic phase is reported to be three orders of magnitude bigger than other ferroelectric LCs - a real game changer! I will take the opportunity to explore this new nematic phase in great detail, with the aim of determining its potential in energy applications.My programme is timely, exciting and ambitious, designed to take fundamental understanding to a stage where engineers or industrial partners can begin to develop the ideas with the greatest potential.