A5083071708- Liquid Crystal Research Advancements
- Molecular spectroscopy and chirality
- Surfactants and Colloidal Systems
- Plant Reproductive Biology
- Nonlinear Dynamics and Pattern Formation
- Photonic Crystals and Applications
- Material Dynamics and Properties
- Photonic and Optical Devices
- Advanced Materials and Mechanics
- Avian ecology and behavior
- Semiconductor Quantum Structures and Devices
- Lipid Membrane Structure and Behavior
- Spectroscopy and Quantum Chemical Studies
- DNA and Nucleic Acid Chemistry
- Theoretical and Computational Physics
- Synthesis and Properties of Aromatic Compounds
- Semiconductor Lasers and Optical Devices
- Nonlinear Optical Materials Research
- Wildlife Ecology and Conservation
- Pickering emulsions and particle stabilization
- Quantum and electron transport phenomena
- Force Microscopy Techniques and Applications
- Optical Polarization and Ellipsometry
- Phase-change materials and chalcogenides
- Fish Ecology and Management Studies
University of Colorado Boulder
2016-2025
University of Colorado System
2011-2024
Moffitt Cancer Center
2024
British Trust for Ornithology
2014-2023
Université Paris-Saclay
2023
Karlstad University
2021
Materials Research Center
2010-2017
Crystal Research (United States)
2003-2016
University of Groningen
2015
Korea Advanced Nano Fab Center
2014
Ferroelectric smectic C (FSC) liquid crystals are used in a simple new geometry that allows the spontaneous formation of either two surface-stabilized monodomains opposite ferroelectric polarization. These domains separated by well-defined walls which may be manipulated with an applied electric field. The resulting electro-optic effects exhibit unique combination properties: microsecond dynamics, threshold behavior, symmetric bistability, and large response.
A smectic liquid-crystal phase made from achiral molecules with bent cores was found to have fluid layers that exhibit two spontaneous symmetry-breaking instabilities: polar molecular orientational ordering about the layer normal and tilt. These instabilities combine form a chiral structure handedness depends on sign of The bulk states are either antiferroelectric-racemic, direction alternating in layer, or antiferroelectric-chiral, which is uniform handedness. Both an electric field–induced...
High-resolution x-ray scattering studies of thin smectic-$C$ ($\mathrm{Sm}C$) samples prepared between solid plates by cooling from the smectic-$A$ phase reveal a surprising "chevron" structure tilted layers. This is formed as response to shrinking $\mathrm{Sm}C$ layers while anchored plates. The layer tilt independent surface treatment. Our results provide fundamental new information on and interactions SmC evidence for defect.
Most populations of migrant shorebirds around the world are in serious decline, suggesting that vital condition-dependent rates such as fecundity and annual survival being affected globally. A striking example is red knot (Calidris canutus rufa) population wintering Tierra del Fuego, which undertakes marathon 30,000 km hemispheric migrations annually. In spring, birds forage voraciously on horseshoe crab eggs Delaware Bay eastern USA before departing to breed Arctic polar deserts. From 1997...
Freeze Fracture Transmission Electron Microscopy (FFTEM) study of the nanoscale structure so-called "twist-bend" nematic (NX) phase cyanobiphenyl (CB) dimer molecule CB(CH2)7CB reveals a stripe texture fluid layers periodically arrayed with bulk spacing d ~ 8.3 nm. Fluidity and rigorously maintained produce long-range-ordered layered focal conic domains. Absence lamellar x-ray reflection at wavevector q 2{\pi}/8 nm-1 or its harmonics in synchrotron-based scattering experiments indicates that...
We report a high-resolution x-ray study of model multilayer fluid membrane system in the lyotropic ${L}_{\ensuremath{\alpha}}$ phase quaternary microemulsion system. The structure factor exhibits power-law behavior characteristic Landau-Peierls As function intermembrane distance $3.8 \mathrm{nm}\ensuremath{\le}d\ensuremath{\le}16.3 \mathrm{nm}$, exponent $\ensuremath{\eta}(d)$ which describes algebraic decay layer correlations is predicted by Helfrich where entropic steric repulsions...
Short complementary B-form DNA oligomers, 6 to 20 base pairs in length, are found exhibit nematic and columnar liquid crystal phases, even though such duplexes lack the shape anisotropy required for ordering. Structural study shows that these phases produced by end-to-end adhesion consequent stacking of duplex oligomers into polydisperse anisotropic rod-shaped aggregates, which can order crystals. Upon cooling mixed solutions short only a small fraction present is complementary,...
The dispersion relations for molecular-orientation fluctuations in a freely suspended ferroelectric smectic-$C$ liquid-crystal film have been determined by inelastic light scattering. geometry appears to be ideal the experimental study of space-time behavior two-dimensional orientational field.
Packing Bananas and Boomerangs Assembling achiral molecules typically generates domains. However, odd things can happen when the are banana-or boomerang-shaped—their cores twist out of plain to form left- or right-handed helices, which then pack into chiral domains that will polarize light (see Perspective by Amabilino ). Hough et al. (p. 452 ) show if you make situation even more complex frustrating packing adjacent layers, create a material appears be macroscopically isotropic with only...
We report the experimental determination of structure and response to applied electric field lower-temperature nematic phase previously reported calamitic compound 4-[(4-nitrophenoxy)carbonyl]phenyl2,4-dimethoxybenzoate (RM734). exploit its electro-optics visualize appearance, in absence field, a permanent polarization density, manifested as spontaneously broken symmetry distinct domains opposite polar orientation. Polarization reversal is mediated by field-induced domain wall movement,...
We have determined the rotational diffusion coefficient (DR) of lysozyme from spectrum depolarized light scattered by this protein. The sample was illuminated a single-frequency He–Ne laser and analyzed using high-resolution spherical Fabry–Perot interferometer. D20,wR to be (16.7 ± 0.8) × 106/sec at 15% protein concentration. have, in addition, measured translational (DT) employing now-familiar techniques optical mixing spectroscopy observe polarized find D20,wT (10.6 0.1) 10−7 cm2/sec,...
The chiral, heliconical (twist-bend) nematic ground state is reported in an achiral, rigid, bent-core mesogen (UD68). Similar to the twist-bend (NTB) phase observed bent molecular dimers, NTB of UD68 forms macroscopic, smectic-like focal-conic textures and exhibits nanoscale, periodic modulation with no associated electron density, i.e., without a detectable lamellar x-ray reflection peak. helical pitch pTB ~ 14 nm. When electric field applied normal helix axis, weak electroclinic effect...
Resonant x-ray scattering shows that the bulk structure of twist-bend liquid crystal phase, recently discovered in bent molecular dimers, has spatial periodicity without electron density modulation, indicating a lattice-free heliconical nematic precession orientation helical glide symmetry. In situ study helix texture for dimer CB7CB an elastically-confined temperature-dependent minimum pitch, but remarkable elastic softness pitch response to dilative stresses. Scattering from is not...
We show that surface interactions can vectorially structure the three-dimensional polariza-tion field of a ferroelectric fluid. The contact between nematic liquid crystal and with in-plane polarity generates preferred orientation polarization at interface. This is route to formation fluid or glassy monodomains high without need for electric poling. For example, unidirectional buffing polyimide films on planar surfaces give quadrupolar anisotropy also induces mac-roscopic polar order...
We have structurally characterized the liquid crystal (LC) phase that can appear as an intermediate state when a dielectric nematic, having polar disorder of its molecular dipoles, transitions to almost perfectly polar-ordered ferroelectric nematic. This phase, which fills 100-y-old void in taxonomy smectic LCs and we term "smectic ZA," is antiferroelectric, with nematic director polarization oriented parallel layer planes, alternating sign from 180 Å period. A Landau free energy, originally...
Numerous measurements of the dielectric constant <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>ɛ</a:mi></a:math> recently discovered ferroelectric nematic (<b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:msub><b:mi mathvariant="normal">N</b:mi><b:mi mathvariant="normal">F</b:mi></b:msub></b:math>) liquid crystal (LC) phase report extraordinarily large values <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mi>ɛ</e:mi></e:math>′ (up to ∼30 000) in <f:math...
Simultaneous manipulation of multiple degrees freedom light lies at the heart photonics. Nonlinear wavefront shaping offers an exceptional way to achieve this goal by converting incident into beams new frequencies with spatially varied phase, amplitude, and angular momenta. Nevertheless, reconfigurable control over structured fields for advanced multimode nonlinear photonics remains a grand challenge. Here, we propose concept geometric phase in emerging ferroelectric nematic fluid, which...
Abstract We present a new ferroelectric nematic material, 4-((4′-((trans)-5-ethyloxan-2-yl)-2′,3,5,6′-tetrafluoro-[1,1′-biphenyl]-4-yl)difluoromethoxy)-2,6-difluorobenzonitrile (AUUQU-2-N) and its higher homologues, the molecular structures of which include fluorinated building blocks, an oxane ring, terminal cyano group, all contributing to large dipole moment about 12.5 D. observed that AUUQU-2-N has three distinct liquid crystal phases, two were found be polar phases with spontaneous...
The current intense study of ferroelectric nematic liquid crystals was initiated by the observation same phase in two independently discovered organic, rod-shaped, mesogenic compounds, RM734 and DIO. We recently reported that compound also exhibits a monotropic, low-temperature, apolar having reentrant isotropic symmetry (the IR phase), formation which is facilitated to remarkable degree doping with small (below 1%) amounts ionic BMIM-PF6. Here we report similar phenomenology DIO, showing...
We describe the design and synthesis of a ferroelectric liquid crystal composed racemic molecules. The polarization results from spontaneous polar symmetry breaking in fluid smectic. phase is also chiral, resulting formation mixture macroscopic domains either handedness at isotropic-to-liquid transition. This smectic thus conglomerate. Detailed investigation electrooptic current behavior within individual cells shows thermodynamically stable structure to be uniformly tilted bow-phase (banana...
Any polar-ordered material with a spatially uniform polarization field is internally frustrated: The symmetry-required local preference for to be nonuniform, i.e., locally bouquet-like or "splayed." However, it impossible achieve splay of preferred sign everywhere in space unless appropriate defects are introduced into the field. Typically, materials like ferroelectric crystals liquid crystals, such not thermally stable, so that globally frustrated and remains uniform. Here, we report class...