Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session E3: Physics of Liquids II -- Multicomponent and Charged Fluids |
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Sponsoring Units: GSOFT GSNP DCP Chair: Stephen Whitelam, Lawrence Berkeley National Laboratory Room: 262 |
Tuesday, March 14, 2017 8:00AM - 8:12AM |
E3.00001: Relaxation-Excitation Mode Analysis of the Energy Landscape Statistics in Liquids Zhikun Cai, Yang Zhang Despite theoretical and computational advances, a gap still exists between the energy landscape theory and the experimental observables. To bridge this gap, we formulated a relaxation-excitation mode analysis (REMA) framework by incorporating the energy landscape picture into the kinetic theory of liquids. We derived from the Boltzmann equation a coordinate-space relaxation-excitation equation by statistically treating many-body collisions in the locally thermalized ``collision zone''. The elementary relaxation-excitation mode defined by the Green's function of this equation follows a distribution governed by the intrinsic roughness of the energy landscape. Consequently, the experimentally measurable self intermediate scattering function, e.g. from quasi-elastic and inelastic scattering experiments, becomes a joint Laplace-Fourier transform of the relaxation-excitation mode distribution. Numerical inversion unveils the important statistics of activation barriers and basin excitations of the energy landscape. We examined the self-consistency of REMA on three ideal systems analytically and applied REMA to analyze the hydrogen dynamics of liquid water via ab initio molecular dynamics simulations. [Preview Abstract] |
Tuesday, March 14, 2017 8:12AM - 8:24AM |
E3.00002: Charge ordering in ionic fluids mediate repulsive surface interactions Kinjal Dasbiswas, Nicholas B. Ludwig, Hao Zhang, Dmitri Talapin, Suri Vaikuntanathan Recent experiments on ionic fluids, such as surface force measurements in organic ionic liquids \footnote[3]{Smith, A. M., Lee, A. A. \& Perkin, S., J. \emph{Phys. Chem. Lett.}, {\bf 7 (12)}, 2157 (2016)} and the observation of colloidal stability in inorganic molten salts \footnote[4]{Zhang, H. \emph{et al.}, accepted at \emph{Nature} (2016)}, suggest the presence of long-ranged repulsive forces. These cannot be explained within the classical Debye-H{\"u}ckel theory for dilute electrolytes. We argue that such repulsive interactions can arise from long-range (several \emph{nm}) charge density oscillations induced by a surface that preferentially binds one of the ionic species in an ionic fluid. We present a continuum theory that accounts for such charge layering based on a frustrated Ising model that incorporates both long-range Coulombic and short-range steric interactions. The mean-field analytic treatment qualitatively matches results from molecular simulations. A careful analysis of the ionic correlation functions arising from such charge ordering may also explain the long electrostatic screening lengths observed in various ionic fluids and their non-monotonic dependence on the electrolyte concentration. [Preview Abstract] |
Tuesday, March 14, 2017 8:24AM - 8:36AM |
E3.00003: Continuous freezing and melting of water in proximity to nanostructured CuO coatings. J. Torres, Z. N. Buck, H. Kaiser, R. A. Winholtz, H. Taub, T. Tumlin, A. al-Wahish, M. Tyagi, F. Y. Hansen Nanostructured CuO coatings have been used to enhance the performance of heat transfer devices such as oscillating heat pipes.$^{\mathrm{2}}$ Scanning electron microscope images of these coatings show sharp, blade-like features 1$-$3 $\mu $ in length$^{\mathrm{3}}$ yielding surfaces of high hydrophilicity. To assess the strength of the CuO/H$_{\mathrm{2}}$O interaction, we have investigated the freezing/melting behavior of H$_{\mathrm{2}}$O in proximity to these surfaces. Using the backscattering spectrometer (HFBS) at the NIST Center for Neutron Research, we have measured the intensity of neutrons scattered elastically from a well-hydrated sample of CuO-coated Cu foils as a function of temperature. We find that all of the water freezes continuously over the range 280 K to 200 K, suggesting the formation of amorphous ice. In addition, preliminary quasielastic spectra at 250 K show broadening at all $Q$ values, indicating slower dynamics than for bulk supercooled water at this temperature. Neutron diffraction measurements are in progress at the University of Missouri Research Reactor to confirm the absence of hexagonal ice Bragg peaks as we have been found for well-hydrated single-supported bilayer membranes (DMPC).$^{\mathrm{4}}$ $^{\mathrm{2}}$F. Z. Zhang \textit{et al}., J. Heat Transfer \textbf{138}, 062901 (2016). $^{\mathrm{3}}$Y. Nam and Y. S. Ju, J. Adhesion Science and Technology \textbf{27}, 2163 (2013). $^{\mathrm{4}}$M. Bai \textit{et al}., EPL \textbf{98}, 48006 (2012); Miskowiec \textit{et al}., EPL \textbf{107}, 28008 (2014). [Preview Abstract] |
Tuesday, March 14, 2017 8:36AM - 8:48AM |
E3.00004: Proton Transports in Pure Liquid Water Characterized by Melted Ice Lattice Model. Binbin Jie, Chihtang Sah Basic water properties have not been understood for 200 years. Our Melted Ice Lattice model accounts for the 2 basic properties of pure water, the ion product (pH) and mobilities. It has HCP primitive unit cells, each with 4H$_{\mathrm{2}}$O, based on the 1933 Bernal-Fowler model, verified by 1935 Pauling residual entropy theory of 1928-1935 Giauque experimental low temperature specific heat measurements. Our 2 ion species are point-mass protons p$+$ and p-, for mass and electricity transport. Three protonic thermal activation energies are obtained from pH and p$+$ and p- mobilities vs T (0-100$^{\mathrm{O}}$C). Proton transport is analyzed in 3 proton-phonon collision steps: proton detrapping by protonic phonon absorption, proton scattering by oxygenic (water) phonons, and proton trapping with protonic phonon emission. Distinction between Potential and Kinetic Energy Bands of protons (Fermions) and phonons (Bosons) is noted. Experimental protonic activation energies are the phonon energies given by the spring-mass vibration frequencies of lattice, w$_{\mathrm{n}}=$(k$_{\mathrm{n}}$/m$_{\mathrm{n}})^{\mathrm{1/2}}$. n is the proton-mass unit of the synchronized vibrating particles in the primitive unit cells. [Preview Abstract] |
Tuesday, March 14, 2017 8:48AM - 9:00AM |
E3.00005: Observation of ion paring of imidazolium-based ionic liquids in non-polar solvent Doseok Kim, Seoncheol Cha, Minho Lee Ion pairing is an important issue in the practical applications of ionic liquids such as electrolytes in the battery. Ion pairs in solutions of ionic liquids have been classified as (1) fully solvated ions, (2) solvent separated ion pairs, and (3) contact ion pairs. The relative abundance between these three states is determined by the interaction strength between ions (cation-anon), ion-solvent, and solvent-solvent. The solvation and paring of ions have been usually investigated by conductivity measurement as the conductance is considered to come from the free ionic species. However, the techniques to monitor the microscopic structures of ion pairing directly including the contact ion pairs are much desired. Here, the ion pair formation of imidazolium-based ionic liquids having different anions (Cl$^{\mathrm{-}}$, Br$^{\mathrm{-}}$, I$^{\mathrm{-}}$, TFSI$^{\mathrm{-}}$, BF$_{\mathrm{4}}^{\mathrm{-}})$ dissolved in a low-dielectric constant solvent (chloroform) was studied by IR spectroscopy by utilizing a specific vibrational mode of the cation ($\nu $C(2)-H) that changes sensitively with the state of the ion pairing. Ionic liquids having halide anions were fully solvated at lower concentrations of ionic liquids due to the thermodynamic preference. Interestingly, the ionic liquids having strong interaction between cation and anion (e.g. [BMIM]Cl) remained solvated at much higher concentrations as compared to more weakly interacting ionic liquids (e.g. [BMIM]I). [Preview Abstract] |
Tuesday, March 14, 2017 9:00AM - 9:12AM |
E3.00006: Insulator-to-conductor transition in liquid crystal-carbon nanotube nanocomposites Rajratan Basu, Alfred Garvey A small quantity of carbon nanotubes (CNTs) was dispersed in a liquid crystal (LC) and the LC$+$CNT hybrid in the isotropic phase was found to exhibit an insulator-to-conductor transition when an external electric field was applied. This effect was probed by measuring the resistance of the system as a function of applied voltage across the LC cell. In an LC$+$CNT hybrid, the LC molecules self-assemble themselves at the CNT surface due to $\pi -\pi $ electron stacking, creating pseudonematic domains (PNDs) surrounding the CNTs. These CNT-embedded PNDs interact with the external electric field even in the isotropic phase of the LC. When the external field is applied, the PND-encapsulated CNTs start to rotate along the field and form wires due to their natural tendency of entanglement. The CNT-wires eventually short the two electrodes of the LC cell, manifesting an insulator-to-conductor transition in the LC$+$CNT hybrid. Additional studies revealed that the cell spacing and the CNT-concentration had a significant impact on the threshold voltage across the LC cell for the insulator-to-conductor transition process. [Preview Abstract] |
Tuesday, March 14, 2017 9:12AM - 9:24AM |
E3.00007: Physics of Nontraditional Electrorheological and Magnetorheological Fluids G.Q. Gu, R Tao Nontraditional electrorheology (ER) and magnetorheology (MR) are new areas. It started with high demands, such as reducing the viscosity of crude oil and suppressing turbulence to improve crude oil flow in pipelines. Normally, these two goals conflict each other. When the viscosity is reduced, Reynolds number goes up, and the turbulence would get worse. The non-traditional ER and MR have provided unconventional technologies to solve such issues. Different from traditional ER and MR, where the strong electric field or magnetic field is applied in the direction perpendicular to the flow or shearing, the fluid can even be solidified as the viscosity increases dramatically. In nontraditional ER and MR, the electric field or magnetic field is applied in the direction parallel to the flow, the particles are aggregated into short chains along the flow direction by the field, and the fluid viscosity becomes anisotropic. Along the flow direction, the viscosity is reduced, while in the directions perpendicular to the flow, the viscosity is dramatically increased. Thus the turbulence is suppressed; the flow becomes laminar and is further improved by the reduced viscosity along the flow direction. The original conflicted two goals can now be accomplished simultaneously. The new physics began to produce big impacts on energy, food industry, and medical science. [Preview Abstract] |
Tuesday, March 14, 2017 9:24AM - 9:36AM |
E3.00008: Microscopic origin and macroscopic implications of lane formation in mixtures of oppositely-driven particles Stephen Whitelam Colloidal particles of two types, driven in opposite directions, can segregate into lanes [Vissers et al. Soft Matter 7, 2352 (2011); Dzubiella et al. Phys. Rev. E 65, 021402 (2002)]. I will describe some results on this phenomenon obtained by simple physical arguments and computer simulations [Klymko, Geissler, Whitelam, Phys. Rev. E94, 022608 (2016)]. Laning results from rectification of diffusion on the scale of a particle diameter: oppositely-driven particles must, in the time taken to encounter each other in the direction of the drive, diffuse in the perpendicular direction by about one particle diameter. This geometric constraint implies that the diffusion constant of a particle, in the presence of those of the opposite type, grows approximately linearly with Peclet number, a prediction confirmed by our numerics. Such environment-dependent diffusion is statistically similar to an effective interparticle attraction; consistent with this observation, we find that oppositely-driven colloids display features characteristic of the simplest model system possessing both interparticle attractions and persistent motion, the driven Ising lattice gas [Katz, Leibowitz, Spohn, J. Stat. Phys. 34, 497 (1984)]. [Preview Abstract] |
Tuesday, March 14, 2017 9:36AM - 9:48AM |
E3.00009: Rheological and statistical characteristics of the Lennard-Jones fluid undergoing planar Couette flow and second-law violations Bharath Raghavan, Martin Ostoja-Starzewski We use Non-equilibrium Molecular Dynamics (NEMD) simulations to investigate the rheological and statistical properties of molecular fluids interacting via a Lennard-Jones potential undergoing planar Couette flow. From kinetic theory and the Boltzmann equation, we obtain a rheological equation of state that captures the stress-deformation responses exceptionally well. We obtain a shear-rate dependent model for the viscosity, similar to the Cross model, and demonstrate how this model arises naturally from the Boltzmann equation, possessing an inherent scaling parameter that unifies the rheological properties of the LJ fluid. Using thermo-mechanics, we formulate a dissipation function modeling the LJ fluid as a quasilinear fluid. We explore the statistical properties of the shear-stress under isothermal conditions and the tendency to violate the second-law of thermodynamics, from the probability density function obtained using Information theory. We examine the autocorrelation function (ACF), and power spectral density (PSD) of the shear stress, and their dependence on the fluid state-points and applied strain rates to draw inferences regarding the causes of shear-thinning frequently observed in such systems, and provide insight into the structure of the flow. [Preview Abstract] |
Tuesday, March 14, 2017 9:48AM - 10:00AM |
E3.00010: Probing the Structure of a Binary Mixture of Alcohol and Water at Sapphire Interface Alankar Rastogi, Ali Dhinojwala, Mesfin Tsige Many interfacial phenomena like adhesion, wetting, etc. are mainly influenced by the structure of absorbed molecules at the interface. The structure of these adsorbed molecules can control the physical and chemical properties of the interface. Sapphire interface, that is hydrophilic due to the presence of polar OH group, adsorbs water spontaneously. This affinity towards water molecules is attributed to the strong hydrogen bonding interaction between the OH groups of water and sapphire. However, interfacial concentration of molecules can vary from bulk concentration of a binary mixture based on the complexity of interaction between the OH groups of alcohol, water, and sapphire and the length scale at which these interactions can prevail. A better understanding of this system could be provided by combining interfacial spectroscopic technique like Sum-Frequency Generation Vibrational Spectroscopy (SFG) and Molecular Dynamics simulation (MD). In this study, the sapphire/liquid interface was studied with a varying bulk concentration of ethanol and water. [Preview Abstract] |
Tuesday, March 14, 2017 10:00AM - 10:12AM |
E3.00011: Abstract Withdrawn
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Tuesday, March 14, 2017 10:12AM - 10:24AM |
E3.00012: Restrained Glass transition of Graphene Oxide Colloids with Polymers So Youn Kim, Yul Hui Shim, Kyung Eun Lee, Sang Ouk Kim Graphene and its oxidized form of graphene oxide (GO) have been of particular interest in material science due to their exceptional physical properties. However, relatively little attention has been paid to the GO dispersions although the state of dispersions directly affect to the material property. For example, GO can be well-dispersed in water due to their hydrophilic functionalities; however, they easily form gels or glass around 1 wt{\%}, which often act as an obstacle in GO based composite production. Thus, to understand the structure and dispersing mechanism of GO dispersions is an essential step before reaching application level. In this study, we systematically study the GO dispersion at various conditions and examine how GO glass transition is affected by the presence of polymer. An intriguing observation was that adding polymer can effectively retard glass transition of GO in water. Extensive small angle x-ray scattering and rheological studies are employed to probe the GO structures and properties in solutions. [Preview Abstract] |
Tuesday, March 14, 2017 10:24AM - 10:36AM |
E3.00013: Photonic Block Polymer Films Prepared by Enthalpy-Driven Swelling Atsushi Noro, Yusuke Tomita, Yushu Matsushita, Edwin Thomas We report nearly nonvolatile, soft photonic films prepared by enthalpy-driven swelling of lamellar-forming polystyrene-b-poly(2-vinylpyridine) (PS-P2VP) block copolymer thin films with neat tetraethylene glycol or liquid mixture of tetraethylene glycol/small amount of nonvolatile acid. Transmission electron microscopy and ultra-small angle X-ray scattering (U-SAXS) revealed that the interdomain distance of the PS-P2VP photonic film swollen with neat tetraethylene glycol was almost twice as large as that of neat PS-P2VP film. The experimental wavelength of the reflection light from the photonic film was in good agreement with the wavelength estimated from the Bragg condition with using the interdomain distance obtained by U-SAXS. Moreover, the wavelength of reflected light from photonic films was found to be tunable by varying the acid concentration of the solutions used for swelling of the films. [Preview Abstract] |
Tuesday, March 14, 2017 10:36AM - 10:48AM |
E3.00014: Microrheological characterization of thin films and nanoliter droplets using Magnetic Rotational Spectroscopy with ferromagnetic nanorods. Pavel Aprelev, Konstantin Kornev Recent advances in the fields of soft and composite materials have led to the development of Magnetic Rotational Spectroscopy (MRS) - a technique for analysis of microrheological properties of complex fluids such as gels and polymer solutions. MRS requires minute amounts of liquids to be studied and thus allows for direct characterization of viscosity and elasticity of thin films. It relies on rotation of ferromagnetic nanorods uniformly dispersed in the studied solution with a steadily rotating magnetic field. The rotational behavior of the nanorod when the magnetic and viscous drag torques are nearly the same is very sensitive to the rod's magnetization, the liquid's rheology, and the external magnetic field. We have developed an experimental procedure to accurately control the external magnetic field and carefully study this behavior. We have applied MRS to study microrheology of biofluids as well as kinetics of curing of thin polymer films. [Preview Abstract] |
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