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Ruggero Cortini, Xiaolin Cheng, Jeremy C Smith
Electrostatic interactions between DNA molecules have been extensively studied experimentally and theoretically, but several aspects (e.g. its role in determining the pitch of the cholesteric DNA phase) still remain unclear. Here, we performed large-scale all-atom molecular dynamics simulations in explicit water and 150 mM sodium chloride, to reconstruct the potential of mean force (PMF) of two DNA oligomers 24 base pairs long as a function of their interaxial angle and intermolecular distance. We find that the potential of mean force is dominated by total DNA charge, and not by the helical geometry of its charged groups...
January 16, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Marian Chapran, Enrico Angioni, Neil John Findlay, Benjamin Breig, Vladyslav Cherpak, Pavlo Stakhira, Tell Tuttle, Dmytro Volyniuk, Juozas Vidas Grazulevicius, Yuriy A Nastishin, Oleg D Lavrentovich, Peter John Skabara
A new interface engineering method is demonstrated for the preparation of an efficient white organic light emitting diode (WOLED) by embedding an ultra-thin layer of the novel ambipolar red emissive compound 4,4-di-fluoro-2,6-di(4-hexylthiopen-2-yl)-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indacene (bThBODIPY) in the exciplex formation region. The compound shows a hole and electron mobility of 3.3 × 10-4 cm2 V-1 s-1 and 2 × 10-4 cm2 V-1 s-1, respectively at electric fields higher than 5.3 × 105 V cm-1...
January 12, 2017: ACS Applied Materials & Interfaces
Man-Yu Duan, Hui Cao, Yong Wu, Er-Li Li, Hui-Hui Wang, Dong Wang, Zhou Yang, Wan-Li He, Huai Yang
In this study, we demonstrate a novel method for fabricating polymer stabilized cholesteric liquid crystal (PSCLC) films with non-uniform pitch distribution by utilizing two kinds of photo-induced processes. Based on the large HTP temperature dependence of a chiral dopant, polymer networks were formed at two distant temperature points in sequence. The influence of the polymerization conditions on the reflectance properties of PSCLCs before and after polymerization was investigated. The results strongly suggest that the location and bandwidth of the reflection band can be controlled preferably by adjusting the ultraviolet light intensity and irradiation time of UV-light...
January 5, 2017: Physical Chemistry Chemical Physics: PCCP
Yuri M Yevdokimov, Sergey G Skuridin, Sergey V Semenov, Ljubov A Dadinova, Viktor I Salyanov, Efim I Kats
In this research, we observe and rationalize theoretically the transition from hexagonal to cholesteric packing of double-stranded (ds) DNA in dispersion particles. The samples were obtained by phase exclusion of linear ds DNA molecules from water-salt solutions of poly(ethylene glycol)-PEG-with concentrations ranging from 120 mg ml(-1) to 300 mg ml(-1). In the range of PEG concentrations from 120 mg ml(-1) to 220 mg ml(-1) at room temperature, we find ds DNA molecule packing, typical of classical cholesterics...
December 27, 2016: Journal of Biological Physics
Ping Liu, Xin Guo, Fuchun Nan, Yongxin Duan, Jianming Zhang
Iridescent films formed from the self-assembly of cellulose nanocrystals (CNCs) are brittle and difficult to handle or integrate within an industrial process. Here we present a simple approach to prepare iridescent CNC films with tunable pliability and coloration through the addition of ionic liquids (ILs) of 1-allyl-3-methylimidazolium chloride (AmimCl) as plasticizer. By using the un-dried CNC film as filter membrane and ILs solution as leaching liquor, it was found that the filtration process made ILs uniformly interpenetrate into CNC film due to the strong ionic interaction between CNC and AmimCl...
December 27, 2016: ACS Applied Materials & Interfaces
Mingxian Liu, Zhuohao Huo, Tengfei Liu, Yan Shen, Rui He, Changren Zhou
Highly ordered and concentric ring patterns consisting of halloysite nanotubes (HNTs) with hierarchical cholesteric architectures are prepared by evaporation induced self-assembly in a sphere-on-flat geometry. The structure and properties characters of HNTs are firstly investigated. HNTs show perfect tubular morphology in nanoscale with high dispersion stability in water. Upon drying HNTs aqueous suspension in a sphere-on flat confined space, regular concentric HNTs rings are formed on the substrate via a self-assembly process...
December 27, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
P Rofouie, D Pasini, A D Rey
We present a model to investigate the formation of surface patterns in biological materials through the interaction of anisotropic interfacial tension, bending elasticity, and capillarity at their free surfaces. Focusing on the cholesteric liquid crystal (CLC) material model, the generalized shape equation for anisotropic interfaces using the Rapini-Papoular anchoring and Helfrich free energies is applied to understand the formation of multi-length scale patterns, such as those found in floral petals. The chiral liquid crystal-membrane model is shown to be analogous to a driven pendulum, a connection that enables generic pattern classification as a function of bending elasticity, liquid crystal chirality and anchoring strength...
December 15, 2016: Soft Matter
Takatsugu Endo, Shota Hosomi, Shunsuke Fujii, Kazuaki Ninomiya, Kenji Takahashi
We performed structural investigations of cellulose mixed with 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) in the entire concentration range (0-100 mol %) by wide-angle X-ray scattering with the aid of quantum chemical calculations and (13)C solid-state NMR spectroscopy. We particularly focused on a highly concentrated region (≥30 mol %), which has previously been overlooked. At concentrations of 15-30 mol %, a periodic peak corresponding to cellulose chain alignment emerged; this is associated with a lyotropic cholesteric liquid-crystalline phase...
December 15, 2016: Journal of Physical Chemistry Letters
Cornelia Rosu, Shane Jacobeen, Katherine Park, Elsa Reichmanis, Peter Yunker, Paul S Russo
Liquid crystals can organize dispersed particles into useful and exotic structures. In the case of lyotropic cholesteric polypeptide liquid crystals, polypeptide-coated particles are appealing because the surface chemistry matches that of the polymeric mesogen, which permits a tighter focus on factors such as extended particle shape. The colloidal particles developed here consist of a magnetic and fluorescent cylindrically symmetric silica core with one rounded, almost hemispherical end. Functionalized with helical poly(γ-stearyl-l-glutamate) (PSLG), the particles were dispersed at different concentrations in cholesteric liquid crystals (ChLC) of the same polymer in tetrahydrofuran (THF)...
December 13, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Yuna Kim, Michel Frigoli, Nicolas Vanthuyne, Nobuyuki Tamaoki
The first photoresponsive cholesteric liquid crystal comprising a photoisomerizable helical naphthopyran derivative dopant and a nematic liquid crystal is reported. An unprecedented helical twisting power switching ratio of over 90% allowed us to demonstrate multi-cycle rotational motion of micro-objects by UV light irradiation.
December 20, 2016: Chemical Communications: Chem Comm
A Kuhnhold, T Schilling
We present a Monte Carlo simulation study of helical Yukawa rods as a model for chiral liquid crystal mesogens. To simulate the cholesteric phase, we introduce a new simulation method that uses soft walls and self-determined boundary conditions. We observe that the isotropic-nematic phase transition is shifted to lower volume fractions with decreasing salt concentration as well as with increasing internal pitch of the rods. For particular sets of interaction parameters, the sense of the cholesteric pitch inverts, i...
November 21, 2016: Journal of Chemical Physics
Mi-Yun Jeong, Keumcheol Kwak
In this study, we achieved active fine laser tuning in a broad spectral range with dye-doped cholesteric liquid crystal wedge-type cells through temperature control. The spatial pitch gradient of each position of the wedge cell at room temperature was almost maintained after developing a temperature gradient. To achieve the maximum tuning range, the chiral dopant concentration, thickness, thickness gradient, and temperature gradient on the wedge cell should be matched properly. In order to understand the laser tuning mechanism for temperature change, we studied the temperature dependence of optical properties of the photonic bandgap of cholesteric liquid crystals...
November 20, 2016: Applied Optics
Susete N Fernandes, Pedro L Almeida, Nuno Monge, Luis E Aguirre, Dennys Reis, Cristiano L P de Oliveira, António M F Neto, Pawel Pieranski, Maria H Godinho
A new photonic structure is produced from cellulose nanocrystal iridescent films reflecting both right and left circularly polarized light. Micrometer-scale planar gaps perpendicular to the films' cross-section between two different left-handed films' cholesteric domains are impregnated with a nematic liquid crystal. This photonic feature is reversibly tuned by the application of an electric field or a temperature variation.
November 9, 2016: Advanced Materials
Gonzague Agez, Chloé Bayon, Michel Mitov
: Beetles from the genus Chrysina show vivid reflections from bright green to metallic silver-gold as a consequence of the cholesteric liquid crystal organization of chitin molecules. Particularly, the cuticle of Chrysina gloriosa exhibits green and silver stripes. By combining confocal microscopy and spectrophotometry, scanning electron microscopy and numerical simulations, the relationship between the reflectance and the structural parameters for both stripes at the micro- and nanoscales are established...
November 14, 2016: Acta Biomaterialia
S G Skuridin, F V Vereshchagin, V I Salyanov, D P Chulkov, O N Kompanets, Yu M Yevdokimov
The current notion of the organization of molecules in a cholesteric phase is fairly well substantiated in the case of low-molecular-weight compounds. However, this question is open to discussion in the case of double-stranded nucleic acids. In this work, an attempt to compare the well-known data on the structure of cholesteric phases formed by double-stranded DNA molecules and the results of experimental modeling obtained by the authors has been undertaken. The comparison brings leads to assumption regarding the high probability of the existence of both short-range (positional) and long-range (orientational) order in the arrangement of double-stranded DNA molecules in the liquid crystalline phase...
September 2016: Molekuliarnaia Biologiia
Yo Inoue, Hiroshi Moritake
We investigated the possibility of practical applications using cholesteric liquid crystals (ChLCs) with Helfrich deformation, which causes the undulation of the helical structure. Usually, the Helfrich deformation is very unstable and can be obtained only in the transient state for a short time (< 10 s) under continuous field application. Here, we found that a ChLC polymerized with spatial pattern distribution exhibited high durability of the Helfrich deformation. Furthermore, we revealed molecular alignment of the Helfrich deformation by scanning electron microscope...
October 3, 2016: Optics Express
Yong Li, Dan Luo, Rui Chen
We demonstrate random lasing from a scattering system formed by a cholesteric liquid crystal dispersed in glycerol. Strong scattering of light is produced from the interference between the cholesteric liquid crystal microsphere and glycerol and leads to random lasing. The optical properties of random lasing, such as intensity, threshold, and the temperature effect on lasing emission are demonstrated. The random laser is distinguished from the band-edge laser generated within the cholesteric liquid crystal microspheres by analyzing the positions of the photonic band-edge of the cholesteric liquid crystal and the photoluminescence of the doped laser dye...
November 1, 2016: Applied Optics
Jie Xiang, Andrii Varanytsia, Fred Minkowski, Daniel A Paterson, John M D Storey, Corrie T Imrie, Oleg D Lavrentovich, Peter Palffy-Muhoray
A cholesteric liquid crystal (CLC) formed by chiral molecules represents a self-assembled one-dimensionally periodic helical structure with pitch [Formula: see text] in the submicrometer and micrometer range. Because of the spatial periodicity of the dielectric permittivity, a CLC doped with a fluorescent dye and pumped optically is capable of mirrorless lasing. An attractive feature of a CLC laser is that the pitch [Formula: see text] and thus the wavelength of lasing [Formula: see text] can be tuned, for example, by chemical composition...
November 15, 2016: Proceedings of the National Academy of Sciences of the United States of America
O F Aguilar Gutierrez, Alejandro D Rey
Dilute isotropic collagen solutions are usually flow processed into monodomain chiral nematic thin films for obtaining highly ordered materials by a multistep process that starts with complex inhomogeneous flow kinematics. Here we present rigorous theory and simulation of the initial precursors during flow steps in cholesteric collagen film formation. We first extract the molecular shape parameter and rotational diffusivity from previously reported simple shear data of dilute collagen solutions, where the former leads the reactive parameter (tumbling function) which determines the net effect of vorticity and strain rate on the average orientation and where the latter establishes the intensity of strain required for flow-birefringence, both crucial quantities for controlled film formation flow...
November 15, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Oliver Wiese, Davide Marenduzzo, Oliver Henrich
We explore the rheology and flow-induced morphological changes of cholesteric liquid crystal patterns subject to Poiseuille flow within a slab geometry, and under different anchoring conditions at the wall. Our focus is particularly on the behaviour of "Cholesteric Fingers of the first kind" and of Blue Phase II. Depending on the applied pressure gradient, we observe a number of dynamic regimes with different rheological properties. Our results provide the first insight into the flow response of cholesteric phases with fully two- or three-dimensional director field patterns and normal and planar degenerate anchoring conditions as commonly realised in experiments...
November 16, 2016: Soft Matter
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