Polarizing beam splitter cube for circularly and elliptically polarized light

A method of designing an arbitrary polarizing beam splitter (PBS) cube using multiple layers of thin-film liquid crystal polymer is demonstrated. This methodology utilizes cholesteric phase liquid crystal polymer (Ch-LCP) to transmit one handedness of elliptically polarized light and reflect the orthogonal state when unpolarized light is incident. Using additional nematic liquid crystal polymer layers, the polarization state for the transmitted and reflected light can be controlled and output to any two orthogonal states represented on the Poincarte sphere. Two cubes are designed, fabricated, tested, and compared with theory. One cube is constructed with a single layer of Ch-LCP, and another cube is constructed with a layer of Ch-LCP and an additional nematic liquid crystal polymer layer.National Science Foundation (NSF) [1607358]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Light-addressable liquid crystal polymer dispersed liquid crystal

Scattering-free liquid crystal polymer-dispersed liquid crystal polymer (LCPDLC) films are fabricated by combining a room temperature polymerizable liquid crystal (LC) monomer with a mesogenic photosensitive LC. The morphological and photosensitive properties of the system are analysed with polarized optical microscopy and high resolution scanning and transmission electron microscopy. A two-phase morphology comprised of oriented fibril-like polymeric structures interwoven with nanoscale domains of phase separated LC exists. The nanoscale of the structures enables an absence of scattering which allows imaging through the LCPDLC sample without optical distortion. The use of a mesogenic monomer enables much smaller phase separated domains as compared to nonmesogenic systems. All-optical experiments show that the transmitted intensity, measured through parallel polarizers, can be modulated by the low power density radiation (31 mW/cm2) of a suitable wavelength (532 nm). The reversible and repeatable transmission change is due to the photoinduced trans-cis photoisomerization process. The birefringence variation (0.01) obtained by optically pumping the LCPDLC films allow their use as an alloptical phase modulato

Responsive liquid crystal polymer rods

In this dissertation I report on the successful fabrication of anisotropic liquid crystal polymer rods. These polymer rods demonstrated re-orientation by an applied external field. The polymer rods, 200 nm in diameter and a maximum of 60 mum in length, were produced by a template synthesis technique. A reactive liquid crystal monomer was filled into porous Anopore membranes which were used as a confining media. The liquid crystal monomer was polymerized by UV light while the liquid crystal remained in the nematic temperature range. The polymerization process permanently freezes the orientational order of the confined liquid crystal molecules, producing rods that are temperature independent after curing. The curing is kept in the nematic range to ensure proper orientational alignment in the pore of the membrane, where the responsive nature of the rods can be tailored by temperature, external fields, and/or surface treatments. The rods were suspended in low viscosity silicone oil and injected into indium tin oxide coated glass cells.;Both DC and AC electric fields were applied to the electro-optical glass cells, resulting in different types of rod movement. Switching times (time to change orientation from horizontal to vertical) has been observed to be as fast as 0.1 seconds and the threshold voltage has been as low as 5 volts. The switching times of the rods are mainly driven by the strength of the applied field and the molecular orientation of the rods. A model was used to describe the best case scenario of the rod structures and outlines that faster switching times are possible. Translational movement (moving vertical with the rod staying in the horizontal position) was also noted with the DC applied field. AC fields give different types of movement including rotational, vibrating, and swimming motions. The average rotational speed was found to vary linearly with the applied field strength, where the fastest speeds were at the highest field strength. Also, responsive rods were noted to move and push unresponsive rods in and out of the viewing area. The responsive rods are technologically important for possible electro-rheological fluids, magneto-rheological fluids, and components in microfluidic devices

Effect of Ordering on Spinodal Decomposition of Liquid-Crystal/Polymer Mixtures

Partially phase-separated liquid-crystal/polymer dispersions display highly fibrillar domain morphologies that are dramatically different from the typical structures found in isotropic mixtures. To explain this, we numerically explore the coupling between phase ordering and phase separation kinetics in model two-dimensional fluid mixtures phase separating into a nematic phase, rich in liquid crystal, coexisting with an isotropic phase, rich in polymer. We find that phase ordering can lead to fibrillar networks of the minority polymer-rich phase

Reactive mesogens for ultraviolet-transparent liquid crystal polymer networks

Transparency and stability to UV light are important and desirable properties for modern tunable optical elements and active soft robots. A library of novel reactive mesogens for liquid crystal polymer networks resilient and transparent to UV light has been synthetised and characterised. Phase behaviours of the reactive mesogens have been determined by polarised optical microscopy and differential scanning calorimetry. Liquid crystal polymer networks based on the combination of these novel reactive mesogens have been evaluated and compared to those based on common commercially available compounds. The results showed a twofold increase in transparency in a broad UV spectral region (200–400 nm) and importantly showed no degradation upon prolonged UV exposure contrary to the networks composed from commercial counterparts

Threading the spindle: a geometric study of chiral liquid crystal polymer microparticles

Polymeric particles are strong candidates for designing artificial materials capable of emulating the complex twisting-based functionality observed in biological systems. In this letter, we provide the first detailed investigation of the swelling behavior of bipolar polymer liquid crystalline microparticles. Deswelling from the spherical bipolar configuration causes the microparticle to contract anisotropically and twist in the process, resulting in a twisted spindle shaped structure. We propose a model to describe the observed spiral patterns and twisting behavior

Modeling Defects, Shape Evolution, and Programmed Auto-origami in Liquid Crystal Elastomers

Liquid crystal elastomers represent a novel class of programmable shape-transforming materials whose shape change trajectory is encoded in the material's nematic director field. Using three-dimensional nonlinear finite element elastodynamics simulation, we model a variety of different actuation geometries and device designs: thin films containing topological defects, patterns that induce formation of folds and twists, and a bas-relief structure. The inclusion of finite bending energy in the simulation model reveals features of actuation trajectory that may be absent when bending energy is neglected. We examine geometries with a director pattern uniform through the film thickness encoding multiple regions of positive Gaussian curvature. Simulations indicate that heating such a system uniformly produces a disordered state with curved regions emerging randomly in both directions due to the film's up-down symmetry. By contrast, applying a thermal gradient by heating the material first on one side breaks up-down symmetry and results in a deterministic trajectory producing a more ordered final shape. We demonstrate that a folding zone design containing cut-out areas accommodates transverse displacements without warping or buckling; and demonstrate that bas-relief and more complex bent-twisted structures can be assembled by combining simple design motifs.Comment: 11 pages, 7 figure

Development of a test method to determine the relative barrier performance of polymeric films to flavor loss of methyl salicylate

The increased use of polymer films to package a wide range of flavor compounds in various products creates a problem in trying to recommend appropriate materials. There is a need to identify tools that enable the engineer to simplify the selection process through ranking the relative adsorption of such compounds with different polymer films. The study of one such compound, Methyl Salicylate, was conducted for polymer films representing commodity and engineering barrier films. The films tested were Polypropylene, Polyethylene Terephthalate, Polyethylene Napthalate, Aclar, and Liquid Crystal Polymer. The testing was conducted with a Thermogravimetric Analyzer to determine the relative amount of penetrant adsorbed by each film; thereby enabling a ranking of expected barrier performance. The results indicate that the Liquid Crystal Polymer (LCP) film sample had the lowest rate of adsorption of Methyl Salicylate. Further studies are recommended to refine the method and evaluate multiple flavor adsorption behaviors

Carbon Nanotube-Reinforced Thermotropic Liquid Crystal Polymer Nanocomposites

This paper focuses on the fabrication via simple melt blending of thermotropic liquid crystal polyester (TLCP) nanocomposites reinforced with a very small quantity of modified carbon nanotube (CNT) and the unique effects of the modified CNT on the physical properties of the nanocomposites. The thermal, mechanical, and rheological properties of modified CNT-reinforced TLCP nanocomposites are highly dependent on the uniform dispersion of CNT and the interactions between the CNT and TLCP, which can be enhanced by chemical modification of the CNT, providing a design guide of CNTreinforced TLCP nanocomposites with great potential for industrial uses