Understanding the physics of Liquid Crystalline Elastomers and composites

Liquid crystal elastomers (LCEs) are exciting examples of soft matter systems; they combine the properties of polymers and liquid crystals to produce materials with remarkable properties. Some of these are well-known, such as the potential for shape-changing in response to external stimuli such as temperature, light or electric fields. However, the Leeds team recently discovered LCEs as the first synthetic molecular auxetic (negative Poisson's ratio) materials. This is paradigm-shifting; although auxetic materials have been known for about 3 decades, the so-called re-entrant materials that have been studied so far rely on carefully engineered structures that are generally porous and that are formed from positive Poisson-ratio materials. The re-entrant materials are consequently difficult to manufacture, limited in size to structures of the order of tens of microns, and are not transparent. Our LCEs overcome all of these limitations, making them exciting materials that have possible applications in impact and delamination resistance, and as acoustic metamaterials.