No description available.

No description available.

No description available.

A variety of liquid crystalline (LC) materials have been examined as potential membrane separation materials. The order present in the LC phases has measurable effects on solute sorption, diffusivity, permeability, and selectivity, and can thus be used to tune the transport and separation of different species. The current work has focused on polymer dispersed liquid crystal (PDLC), linear butadiene diol based side chain liquid crystalline polymer (LCP), and linear and crosslinked acrylate based LCP membranes. The focus was primarily on the separation of propylene and propane, a separation of significant industrial interest that is not easily achieved with current membrane technology. Polysulfone (Psf) and 4-cyano-4'-octylbiphenyl (8CB) were used to fabricate polymer dispersed liquid crystal (PDLC) membranes. Permeation properties for propane and propylene through polysulfone membranes with increasing LC concentrations were measured at temperatures above and below the glass transition temperature and in several LC phases. The plasticization of PSf by 8CB increased permeability and selectivity with increasing temperatures below the Tg, and membranes with higher LC concentrations exhibited a higher mixed gas permeability and selectivity for propylene. Permeability selectivity decreased across the smectic to nematic phase transition. Overall, selectivities were low, and membrane stability was a significant problem, especially at higher pressures. Thus, several LCP systems were studies as candidates for membrane gas separations. A side chain liquid crystalline poly(butadiene)diol with cyanobiphenyl mesogens was impregnated in a porous PTFE support for gas transport studies. Single gas sorption for propane and propylene in the LCP were investigated in the smectic A mesophase. Gas transport in the glassy state showed separation dominated by differences in gas diffusivity. Permeabilities and selectivities for propylene/propane in the liquid crystal mesophase increased with increasing temperature due to an increase in the segmental motional of the mesogenic units which facilitated solubility of propylene over propane. In addition, an increase solubility differences between propane and propylene were observed with an increase in feed pressure. Mixed gas permeability measurements resulted in an increase in selectivity both below and above the glass transition temperature due to competitive sorption of the two gases. The thermal behavior of liquid crystalline poly(butadiene)diols (PBDs) containing methoxy- or butoxy-substituted azobenzene side chains was studied. A strong dependence of the viscous and dynamic moduli of the polymer with respect to frequency and degree of modification was observed, but the results suggested that prolonged membrane stability for linear poly(butadiene)diol LCPs would be difficult to achieve. As a result, a new class of cross-linkable acrylate based side-chain LCPs was developed. A mesogenic cyanobiphenyl based acrylate monomer, in combination with a non-mesogenic comonomers and a cross-linking agent, was used was used to fabricate stable cross-linked LCP films for membrane separation applications using an in situ free radical polymerization technique with UV initiation. To our knowledge, this is the first reported example of a crosslinked LCP membrane. Increasing the cross-linker content resulted in a decrease in mesogen order. At temperatures in the LC mesophase permeability selectivity for propylene over propane was derived from both solubility and diffusivity selectivity and was higher for the membrane with lower crosslinker content. An increase in the temperature causes a decrease in molecular ordering and consequently decreased permeability selectivity. At temperatures approaching the nematic/isotropic transition and above, the membrane with higher crosslinker content exhibited higher propylene selectivity. Mixed gas studies of propylene/propane resulted in higher selectivities compared to the single gas runs due to the decrease of propane permeability by the presence of propylene. / Ph. D.

No / The ability of a cell to contract plays an important role in determining the ability of the cell to migrate, proliferate and associating with other cells. The transduction of the force in soft substrate such as the liquid crystal surface is a method proposed to study the traction forces of single cells. In this work, finite element method was used to study the compressive forces induced by the keratinocyte to the liquid crystal surface via the anchorage of focal contacts. The constitutive finite element model of the liquid crystal-focal contacts was established. The stress and displacement were analyzed using linear static stress analysis for a quiescent cell. The data for lateral displacements obtained from the experiment were provided as inputs to develop the model and verified through the output acquired for both simulation and experiment. The simulation results indicated that the cell compressive stresses were in the range of 14.93 ± 1.9 nN/μm2 per focal contact. Based on the result obtained, it was suggested to model focal contact-liquid crystal interface with a compressive model that can better approximate the mechanism observed

No description available.

The recent interest in bent core liquid crystal has shown many unique physical properties, such the anomalous behaviour of the elastic constants (SplayK1, Twist K2, and BendK3). In bent core liquid crystals it is observed that K3K1). Such behaviour is analogous to calamitic liquid crystals but is in contrast to all other bent-core nematic materials reported to date. Such a result questions some of the current explanations for the elastic behaviour of bent-core materials. Using molecular field theory and atomistic modelling the different elastic behaviour predicted is again in excellent agreement with experimental results. The bend angle is again shown to be an important part in determining the physical properties of bent-core nematic liquid crystals. In a mixture from an oxadiazole dopant and calamitic host liquid crystal, it was found that a filament structure appears in the nematic phase. The filaments appear to interfere with the measurements for elastic constants. In order to understand the filament structure many methods were used including SAXS, dielectric permittivity, and DSC. It was found that the mixture had formed a gel - like phase. The gel is composed of a liquid crystal network and a liquid crystal background, not seen before in any gel system. Due to the liquid crystalline properties both the network and the background can be aligned and manipulated. The new gel phase can possess many new unique properties which warrant further studies understand further into how fundamentally the phase is forming.

In this thesis we synthesize two organic materials, one is discotic liquid crystal Acid-6, and the other is novel discotic liquid crystal polymer DLC-PAM. After demonstrating the molecular structures of Acid-6 and DLC-PAM by FT-MS, 1H-NMR and FT-IR, we use the two materials as photo-sensitized dyes for dye-sensitized solar cells(DSSCs) and manufacture two kinds of cells. We use polyacrylamide(PAM) as main chain of the novel discotic liquid crystal polymer DLC-PAM and graft the discotic liquid crystal monomer Acid-6 onto PAM by chemical synthesis. DLC-PAM belongs to side-chain liquid crystal polymer, and it can show the properties of it¡¦s discotic liquid crystal function. One of the properties is absorption of visible light. By observing the UV-Vis spectrum, we can realize the absorption band is located between 200 ~ 450 nm and confirm that it is able to be a photo-sensitized dye. Another property of discotic liquid crystal is the self-assembly ability, the moleculars can assemble into hexagonal columnar structure by themselves, and the property enable discotic liquid crystal to have better mobility. In this part, we can demonstrate DLC-PAM and Acid-6 really have hexagonal columnar structure by X-ray diffractmeter. After qualitative demonstrating and optical analysis, we use DLC-PAM and Acid-6 as photo-sensitized dyes for DSSCs and manufacture two kinds of cells successfully. The more photocurrent occur when the two DSSCs are woking. Besides, the two DSSCs have good performance on power conversion efficiency which can achieve 0.047 % for DLC-PAM and 0.364 % for Acid-6. Therefore, in this research we prove that DLC-PAM and Acid-6 are able to be photo-sensitized dyes for DSSCs and successfully demonstrate that using the two materials to manufacture DSSCs is feasible.

Chiral Liquid Crystals (CLCs) can selectively reflect light of a specific wavelength when the period of its helically twisted structure is appropriately chosen and white light propagates along the helical axis. This phenomenon makes CLCs attractive for reflective-color display, without the needs of backlighting, polarizers, or color filters. Polymer Dispersed Chiral Liquid Crystals (PDCLC) have been developed for reflective switchable, bistable color display. However they suffer from high external driving voltage, low reflectivity, and high cost in pretreatment of the substrates. The key to solve these problems is to understand and control the anchoring behavior of CLC at a polymer surface. This research has two purposes: to develop PDCLC films with high reflectivity and to investigate the factors affecting the anchoring behavior of CLC at the polymer surface of the film. Specifically, commercially available chiral dopant and nematic liquid crystals were carefully chosen to formulate the CLCs reflecting different color. These CLCs are mixed with various acrylate and methacrylate monomers respectively, and UV cured at varied conditions to obtain PDCLC films. The anchoring behavior of these films is characterized using polarized optical microscopy, confocal microscopy, and microscopic-spectrophotometer. The factors influencing the anchoring behavior include chemical structure of the monomers, effective diameter of individual cells in PDCLC, thickness of individual cells in PDCLC, and the pitch of CLC, among which the chemical structure of the monomers is the most important. The PDCLC film made with n-hexyl methacrylate is found to selectively reflect light with the reflectivity larger than that of pure CLC with the same pitch.

The study proposed a high efficient dye sensitize solar cell (DSSC) by embedding liquid crystal in liquid electrolyte. When liquid crystal molecules was disperse in the liquid electrolyte, the light-scattering occur due to refractive index mismatching by randomly oriented liquid crystal droplets. The light-scattering allows solar light have longer optical path length within the solar cell and therefore enhances light-trapping efficiency of N719 dye. The experiment results reveal that the DSSC with the liquid crystal concentration of 20 wt% have best electric conversion efficiency. Moreover, the study also introduces chloseteric liquid crystal to the liquid electrolyte of a DSSC and compare with nematic liquid crystal embedded DSSC. The cholesteric liquid crystal with periodic helical structure in the liquid electrolyte provides not only light-scattering but also selective reflection. Compared with nematic liquid crystal embedded DSSC, the cholesteric liquid crystal embeded DSSC has a more large light-trapping efficiency due to combined effects of light scattering and selective reflection. Besides, when the reflective band (480~580nm) of cholesteric liquid crystal is matched to the absorption spectrum of N719 dye, the DSSC has better photoexcitation of dye and photovoltaic performance.