2018年 9月4日(土) 14:40-15:40
“Biaxial molecular-colloidal nematic liquid crystals”
Coexistence of order and fluidity enables functioning of biological membranes and liquid crystal displays alike, but only a few of many possible distinct realizations of such ordered fluid states have been demonstrated so far. I will discuss how we disperse micrometer-long inorganic colloidal rods in a nematic fluid host of nanometer-long rod-like organic molecules . These building blocks, while freely diffusing around, interact to spontaneously form an orthorhombic biaxial nematic fluid, in which like-sized rods are roughly parallel and the molecular ordering direction is orthogonal to that of colloidal rods. Using nonlinear optical microscopy and Raman spectroscopy, we study the low-symmetry orientational distributions of both molecular and colloidal rods. We construct a detailed temperature-concentration phase diagram that contains two uniaxial and one biaxial nematic phases, as well as two-phase coexistence regions . Displaying properties of biaxial optical crystals, our hybrid molecular-colloidal fluids can be switched by electric and magnetic fields and promise a host of technological uses ranging from new breeds of displays to metamaterials. I will discuss how similar ideas can be dextended to colloidal inclusions with other shapes and how they enable realization non-othorhombic biaxial nematics and polar ordered fluids with low symmetry and high degrees of orientational order.
1. Mundoor, S. Park, B. Senyuk, H. Wensink and I. I. Smalyukh. “Hybrid molecular-colloidal liquid crystals.” Science 360, 768-771 (2018).
2. Liu, P.J. Ackerman, T. C. Lubensky and I. I. Smalyukh. “Biaxial ferromagnetic liquid crystal colloids.” Proc. Natl. Acad. Sci. U.S.A. 113, 10479–10484 (2016).