(186ai) Reorientation Dynamics and Symmetry-Breaking of Confined Nematic Liquid Crystal Domains

Liquid crystals (LCs) refer to a class of materials which have anisotropic properties. They are used in many technological applications ranging from displays to biological sensors. One example of a category of technologically relevant LC applications is optical functional materials, which include polymer-dispersed liquid crystal (PDLC) films, sometimes referred to as "smart" windows. In these films, non-deformable micron-scale LC droplets are dispersed in a solid polymer matrix. Application of an electric field through the thickness of a PDLC film results in "switching" between a transparent "on" state (field-on) and a translucent "off" state (field-off).

In this work, orientationally-ordered nematic LC phase formation and external electric field-switching dynamics of non-deformable droplets are studied using the continuum Landau-de Gennes model. The model is able to capture phase transition and reorientation dynamics on device-relevant length and time scales when combined with numerical methods such as the finite element method. Formation dynamics correspond to transitioning from a high-temperature disordered liquid phase to an orientationally-ordered phase referred to as a nematic LC. Field-switching dynamics correspond to the imposition and release of an external (electric) field. The effects of non-spherical shape is studied, which may form naturally or intentionally under controlled conditions in the manufacturing of PDLC films. The interactions between shape, LC/polymer interfacial effects, electric field strength, and other parameters are investigated using fully three-dimensional transient simulations. Additionally, simulation results predicting a symmetry-breaking phase transformation process for sub-micron scale spherical droplets are presented.