Tilt Angle Generation for Nematic Liquid Crystal on Blended Homeotropic Polyimide Layer Containing Trifluoromethyl Moieties

Abstract

We investigate theoretically the application of tailored incoherent far-infrared fields in combination with laser excitation of a single rovibrational transition for rotational cooling of translationally cold polar diatomic molecules. The cooling schemes are effective on a timescale shorter than typical unperturbed trapping times in ion traps and comparable to obtainable confinement times of neutral molecules.

Bifurcation properties of nematic liquid crystals exposed to an electric field: Switchability, bistability, and multistability

“…with D (dimensionless dielectric coefficient), F (dimensionless field strength), A {0,1} (dimensionless surface energy) and α {0,1} (anchoring angles) given by Eqs. (4), (6) and (7). An initial condition θ(x, z, 0) closes the model.…”

“…We have taken a basic but promising 1D model for a bistable LCD device [2], and investigated how it behaves under a specific class of spatial perturbations to the anchoring boundary conditions (sinusoidal perturba- tions to the anchoring angles at the flat bounding surfaces). While more general periodic boundary perturbations could be considered, we restrict attention to those of the form (7), because they afford a manageable parameter space to study, and because we believe the results will be representative of the more general case. Such pertur- bations to the anchoring angles could be due to periodic chemical gradients imposed at the surfaces, or may be thought of as approximating a device with periodic topographical variations.…”

“…Since we require bistability in the absence of an applied field, anchoring conditions at the bounding surfaces z * = 0, h * are key. The anchoring pretilt angle (denoted by α in our model, the preferred value of θ at either interface) may be controlled by a variety of surface treat- ments; for example, mechanical or chemical treatments, nano-patterning, and surface irradiation, have all been shown to produce certain desired anchoring angles [5][6][7][8][9][10][11][12][13][14][15][16][17] with a high degree of control. The anchoring strength A * may also be controlled to some extent [9,11,13,14] by similar methods.…”

Bistable nematic liquid crystal device with flexoelectric switching

“…Much liquid crystal research is devoted to the creation of "designer" surfaces with (stable) specified anchoring properties, and much progress has been made in this direction [6,13,25,30,31]. By suitable treatments it is now possible to engineer a surface at which the NLC molecules have a large, predictable, polar pretilt angle (the anchoring angle α) [25,30].…”

Fabrication of pseudo-pi vertical alignment mode liquid crystal devices with ultra-violet polymerisation and investigations of their electro-optical characteristics

“…Namely, when the LC surface tension is greater than the alignment film surface tension (hydrophobic surface with low surface tension), the LC molecules would be vertically aligned; for the converse, they would be horizontally aligned. In addition, the means through which one can control the pre-tilt angle of the LC molecules include applying differential unidirectional rubbing on the polymer alignment film [11,14,15,22,23,26,27,155,156], importing alkyl long carbon side chain or hydrophobic functional groups into the polymer alignment film in order to reduce the polarity of the alignment film surface and increase the pre-tilt angle of LC molecules [43,71,74,81,[157][158][159][160][161][162], and the use of UV light irradiation or plasma treatment to process the alignment film surface [22,74,163]. In this study, we conducted a preliminary investigation of the interactions between the LC molecules and the alkyl long carbon chains through measurements of the electro-optical characteristics, by varying the different carbon chain lengths of the alkyl acrylic monomer (to simulate the functions of the alkyl side chains of the traditional vertical alignment type PI).…”