A5084184050- Liquid Crystal Research Advancements
- Surfactants and Colloidal Systems
- Molecular spectroscopy and chirality
- Material Dynamics and Properties
- Nonlinear Dynamics and Pattern Formation
- Micro and Nano Robotics
- Plant Reproductive Biology
- Microtubule and mitosis dynamics
- Theoretical and Computational Physics
- Photonic Crystals and Applications
- Pickering emulsions and particle stabilization
- Modular Robots and Swarm Intelligence
- Advanced Thermodynamics and Statistical Mechanics
- Advanced Materials and Mechanics
- Synthesis and Properties of Aromatic Compounds
- Fluid Dynamics and Thin Films
- Optical Polarization and Ellipsometry
- Genomics and Chromatin Dynamics
- Lipid Membrane Structure and Behavior
- Phase Equilibria and Thermodynamics
- Cellular Mechanics and Interactions
- Electrostatics and Colloid Interactions
- Protein Structure and Dynamics
- Stochastic processes and statistical mechanics
- Spectroscopy and Quantum Chemical Studies
University of Colorado Boulder
2016-2025
Université Paris-Saclay
2023
Flatiron Health (United States)
2022
Flatiron Institute
2022
University of Colorado System
2003-2021
Otto-von-Guericke University Magdeburg
2011
Crystal Research (United States)
2009
Ferro (United States)
1999-2006
Queen's University
2001
Chalmers University of Technology
1999
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...
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,...
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...
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...
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...
A variety of simple bent-core molecules exhibit smectic liquid crystal phases planar fluid layers that are spontaneously both polar and chiral in the absence crystalline order. We found because intralayer structural mismatch, such also only marginally stable against spontaneous saddle splay deformation, which is incompatible with long-range This results macroscopically isotropic fluids possess short-range orientational positional order, broken symmetry chirality--even though formed from...
The ferroelectric properties of bent-core liquid crystalline molecules emerge from ordering within the smectic layers.
Microtubules and motor proteins are building blocks of self-organized subcellular biological structures such as the mitotic spindle centrosomal microtubule array. These same ingredients can form new ``bioactive'' liquid-crystalline fluids that intrinsically out equilibrium which display complex flows defect dynamics. It is not yet well understood how microscopic activity, involves polarity-dependent interactions between microtubules, yields larger-scale dynamical structures. In our...
Abstract Ferrofluids are familiar as colloidal suspensions of ferromagnetic nanoparticles in aqueous or organic solvents. The dispersed particles randomly oriented but their moments become aligned if a magnetic field is applied, producing variety exotic and useful magnetomechanical effects. A longstanding interest challenge has been to make such macroscopically ferromagnetic, that having uniform alignment the absence field. Here we report fluid suspension nanoplates spontaneously aligns into...
The organic mesogens RM734 and DIO are members of separate molecular families featuring distinct structures. These the first ones known to exhibit a ferroelectric nematic liquid crystal phase. Here, we present an experimental investigation phase diagram electro-optics binary mixtures DIO. We observe paraelectric phases in both materials, each which exhibits complete miscibility across diagram, showing that same Remarkably, these molecules form ideal with respect paraelectric–ferroelectric...
We report the smectic $A_F$, a new liquid crystal phase of ferroelectric nematic realm. The $A_F$ is small polar, rod-shaped molecules which form two-dimensional fluid layers spaced by approximately mean molecular length. uniaxial, with director, local average long-axis orientation, normal to layer planes, and ferroelectric, spontaneous electric polarization parallel director. Polarization measurements indicate almost complete polar ordering $\sim 10$ Debye longitudinal dipoles, hysteretic...
The twist-bend nematic liquid crystal phase is a three-dimensional fluid in which achiral bent molecules spontaneously form an orientationally ordered, macroscopically chiral, heliconical winding of ten nanometer-scale pitch the absence positional ordering. Here, structure dimer CB7CB and its mixtures with 5CB characterized, revealing hidden invariance self-assembly CB7CB, such that over wide range concentrations temperatures, helix cone angle change as if ground state for TB inextensible...
We use both mean-field methods and numerical simulation to study the phase diagram of classical particles interacting with a hard-core repulsive, soft shoulder. Despite purely repulsive interaction, this system displays remarkable array aggregate phases arising from competition between shoulder length scales. In limit large width core size, we argue that has number universal features, classify set shoulders lead aggregation at high density. Surprisingly, sequence size adjusts so as keep...
A physical model that exhibits de novo bipolar spindle assembly is used to study the mechanisms of bipolarity.
The essential functions required for mitotic spindle assembly and chromosome biorientation segregation are not fully understood, despite extensive study. To illuminate the combinations of ingredients most important to align segregate chromosomes simultaneously assemble a bipolar spindle, we developed computational model fission-yeast mitosis. Robust requires progressive restriction attachment geometry, destabilization misaligned attachments, force dependence. Large length fluctuations can...
We have studied the three-component liquid crystal mixture reported to exhibit 'thresholdless antiferroelectricity' [Inui et al., J. Mater. Chem., 1996, 6, 671]. find that thresholdless or V-shaped switching is obtained in absence of antiferroelectricity. This analog electro-optic response due field-induced a twisted smectic C* structure stabilized by polar surface interactions and electrostatic bulk polarization charge interactions. The latter confine director twist thin regions leaving...
The growth of helical filaments in the B4 liquid-crystal phase was investigated mixtures bent-core and calamitic mesogens NOBOW 8CB. Freezing-point depression led to nucleation directly from isotropic mixtures, forming large left- right-handed chiral domains that were easily observed microscope. We show these are composed homochiral formed a process starts nucleus arbitrary chirality continues with chirality-preserving filaments. A model accounts for local homochirality coherence branched is...
Many soft-matter and biophysical systems are composed of monomers that reversibly assemble into rod-like aggregates. The aggregates can then order liquid-crystal phases if the density is high enough, ordering promotes increased growth Systems display coupled aggregation include wormlike micelles, chromonic liquid crystals, DNA RNA, protein polymers fibrils. Coarse-grained molecular models capture key features common to many different lacking; in particular, roles monomer aspect ratio...