US Ireland R&D Partnership: Ferroelectric and Electroclinic Effects in Nano-particle Doped de Vries Smectic Liquid Crystals: Molecular Organisation and Order

Kent State University, Kent OH

Investigators

Abstract

Non-Technical Abstract: The liquid crystal technology currently used in flat panel displays has reached the limits of switching speed and contrast ratio, and cannot meet the requirements of next generation of high-performance displays. Two relatively new and less studied liquid crystal switching phenomena, known as the electroclinic and ferroelectric effects, hold the promise of more than a thousand times faster switching speeds and much higher contrast than the present liquid crystal displays. With support from the Solid State and Materials Chemistry Program in the Division of Materials Research, this interdisciplinary research team under the US Ireland R&D Partnership program of the National Science Foundation seeks to design and synthesize new liquid crystal molecules that optimize these switching phenomena, study the molecular organization and response of these materials to applied electric fields, investigate the role of dissolved nano-particles of different shapes and sizes in improving their performance, and develop protocols and processes leading to the fabrication of proof-of-concept display cells based on these two transformative technologies. The project brings together graduate students, and junior and senior researchers from the US, Ireland, and Northern Ireland and provides them with opportunities to collaborate and acquire diverse sets of technical skills not available in any one laboratory. The project educates students in cutting edge experimental and analytical techniques such as micro-Raman scattering, specialized optical methods, and high-resolution synchrotron x-ray studies at the Advanced Photon Source (Argonne National Laboratory) and the National Synchrotron Light Source (Brookhaven National Laboratory). Participation in research activities during summer by undergraduate students at Kent State University and from (two-year) Stark State College, science demonstrations at local schools, and laboratory visits by K-12 students are among the key educational components of the project. Technical Abstract: de Vries smectic liquid crystals exhibit negligible thermal expansion and hence offer an important and perhaps the only pathway to technological applications of their ferroelectric and electroclinic properties. This US Ireland R&D Partnership project strives to understand the phenomena underlying the remarkable thermal characteristics, the electroclinic and ferroelectric effects, their dependence on molecular structure, and to develop the essential surface alignment protocols required for device applications. The research team plans to synthesize and study molecules with different ratios of siloxane to hydrocarbon segments, chiral centers, and per fluorinated molecules with a hydrocarbon end-segment to acquire the ability to predict their behavior from molecular structure. This is achieved using state-of-the-art experimental techniques such as synchrotron X-ray diffraction, Raman and IR scattering, and wideband dielectric spectroscopy. Determination of the orientational order parameters, orientational distribution function, director tilt order parameter, and smectic order parameter are critical in resolving which of the theoretical models, diffuse cone or sugarloaf, is valid. Doping of liquid crystals with nano-particles, -rods, and -discs is planned to improve the response time, threshold voltage, and contrast ratio. The project team plans to acquire a comprehensive understanding of these systems and demonstrate proof-of-concept new generation electroclinic and ferroelectric liquid crystal devices for displays, optical communications, and sensor applications.