电场对含高氯酸锂盐的互穿网络高分子快离子导体的电导的影响

研究了直流电场对含ＬｉＣｌＯ４的聚氧化乙烯（ＰＥＯ）４００与环氧树脂形成的液晶态互穿网络高分子忆禽子导体的电导率的影响。在室温至９０℃范围内，电导率随外加电压增加面降低。外加电压越高，对电导率变化的影响越大。     

Molecular dynamics simulations of ion transport through carbon nanotubes. II. Structural effects of the nanotube radius, solute concentration, and applied electric fields

The reported work extends previously published research on transport in aqueous ionic solutions through carbon nanotubes. Specifically, the effects of the nanotube radius, solute concentration, and applied external electric fields on the solution structuring are investigated in terms of spatial density distributions, pair distribution functions, and electrostatic potential profiles. Several simulated structural features are consistent with general theoretical results of nanofluidics and can be interpreted fairly well with respect to these (such as the Donnan-type voltages established at the channel apertures depending on the logarithm of the maximum ion concentration). The simulated properties are based on averages over the largest data collection times reported in the literature (0.8 μs), providing accurate estimates of the measured quantities.     

Organic anions: IX. Applications of point charge and HSE force field models to group 1 organometallic terameric and hexameric aggregates

The relative dimensions of group 1 (RM)₄ tetramers can be accounted for in terms of a simple point charge electrostatic model. Such a model cannot be applied to the equivalent (RM)₆ hexamers, but for these a hard sphere electrostatic model is reasonably successful. The findings support the view that the structures of group 1 organometallics are determined principally by electrostatic factors but not the argument that bonding in these compounds is wholly ionic.     

Design considerations for a practical electrostatic micro-motor

Magnetic motors and actuators dominate the large-scale motion domain. For smaller, micro-mechanical systems, electrostatic forces appear more attractive and promising than magnetic forces. Despite their distinguished history, electrostatic motors have found few practical applications because of the high voltages and mechanical accuracies traditionally required. This paper explores the design of electrostatic motors utilizing the advances in silicon technology. Using silicon wafers, and the associated insulators, conductors, anisotropic etching and fine-line photolithographic techniques, it is possible to develop large electrostatic fields with moderately high voltages (≈100 V) across insulators of well-controlled thickness. We present two preliminary designs and numerical simulations: one for a linear electrostatic motor and one for a rotary electrostatic motor.     

An electrostatic elliptical mirror for neutral polar molecules

Focusing optics for neutral molecules finds application in shaping and steering molecular beams. Here we present an electrostatic elliptical mirror for polar molecules consisting of an array of microstructured gold electrodes deposited on a glass substrate. Alternating positive and negative voltages applied to the electrodes create a repulsive potential for molecules in low-field-seeking states. The equipotential lines are parallel to the substrate surface, which is bent in an elliptical shape. The mirror is characterized by focusing a beam of metastable CO molecules and the results are compared to the outcome of trajectory simulations.     

A Three-Dimensional Velocity-Map Imaging Setup Designed for Crossed Ion-Molecule Scattering Studies

In this study, we report the design and simulation of an electrostatic ion lens system consisting of 22 round metal plates. The opening of the extractor plate is covered with metal mesh, which is for shielding the interaction region of the lens system from the high DC voltages applied to all other plates than the repeller and extractor plates. The Simion simulation shows that both velocity-mapping and time focusing can be achieved simultaneously when appropriate voltages are applied to each of the plates. This makes the ion lens system be able to focus large ionic volumes in all three dimensions, which is an essential requirement for crossed ion-molecule scattering studies. A three-dimensional ion velocity measurement system with multi-hit and potential multi-mass capability is built, which consists of a microchannel plate (MCP), a P47 phosphor screen, a CMOS camera, a fast photomultiplier tube (PMT), and a high-speed digitizer. The two velocity components perpendicular to the flight axis are measured by the CMOS camera, and the time-of-flight, from which the velocity component along the flight axis can be deduced, is measured by the PMT. A Labview program is written to combine the two measurements for building the full three-dimensional ion velocity in real time on a frame-by-frame basis. The multi-hit capability comes from the fact that multiple ions from the camera and PMT in the same frame can be correlated with each other based on their various intensities. We demonstrate this by using the photodissociation of CH₃I at 304 nm.     

Intra-cell ionic properties of twisted nematic liquid crystal cells

Under 1-kHz and low-frequency driving, we report our investigation of intra-cell ionic properties of two twisted nematic (TN) liquid crystal (LC) cells made of same LC mixture but different polyimide (PI) materials for LC alignments. A heterodyne interferometry system was used to measure the phase retardations of the TN cells versus applied voltages at 1 kHz. We also measured the phase retardations and currents of the TN cells versus time by applying a mid-grayscale voltage of 1.3 V at 0.1 Hz to the cells. Related to the above-measured data, we have developed equations to characterise the field-driven transports of mobile charge carriers within the PI films independently from that within the LC medium of same TN cell to obtain time-dependent in-cell voltages of mobile charge carries across the LC mixture and across two PI-alignment films, respectively. Our experimental methods can be used to optimise LC mixtures and PI materials for low-refresh-rate thin-film-transistor-driven liquid crystal displays (LCDs) for low power and provide bases for further investigations on mobile-charge-carrier generation and transport within thin in-cell PI-alignment films as well as within the LC mixture of same LC cell.     

Adsorption of highly charged polyelectrolytes onto an oppositely charged porous substrate

The adsorption behavior of highly charged cationic polyelectrolytes onto porous substrates is electrostatic in nature and has been shown to be highly dependent on the polyelectrolyte properties. Copolymers of acrylamide (AM) and diallyldimethylammonium chloride (DADMAC) were synthesized to have a range of macromolecular properties (i.e., charge density and molecular mass). Traditional titration methods have been complemented by fluorescence labeling techniques that were developed to directly observe the extent that fluorescently labeled poly(AM- co-DADMAC) adsorbs into the pore structure of a cellulosic substrate. Although contributing to the electrostatic driving force, the charge density acts to limit adsorption to the outermost surface under electrolyte-free conditions. However, adsorption into the pores can occur if both the molecular mass and charge density of poly(AM- co-DADMAC) are sufficiently low. Adsorption initially increases as the electrolyte concentration is increased. However, the electrostatic persistence length of poly(AM- co-DADMAC) restricts the polyelectrolyte from entering the pores. Therefore, changes in the adsorption behavior at moderate electrolyte concentrations have been attributed to swelling of the polyelectrolyte layer at the fiber exterior. The adsorption behavior changes again at high electrolyte concentrations such that poly(AM- co-DADMAC) could adsorb into the pore structure. This occurred when the electrolyte concentration was sufficient to screen the electrostatic persistence length of poly(AM- co-DADMAC), provided that the entropic driving force for adsorption still existed. It is suggested that adsorption into the pore structure is a kinetic process that is governed by localized electrostatic interactions between poly(AM- co-DADMAC) and the charges located within the pores.     

Analytic first and second derivatives of the energy in the fragment molecular orbital method combined with molecular mechanics

Analytic first and second derivatives of the energy are developed for the fragment molecular orbital method interfaced with molecular mechanics in the electrostatic embedding scheme at the level of Hartree-Fock and density functional theory. The importance of the orbital response terms is demonstrated. The role of electrostatic embedding upon molecular vibrations is analyzed, comparing force field and quantum mechanical treatments for an ionic liquid and a solvated protein. The method is applied for 100 protein conformations sampled in molecular dynamics (MD) to take into account the complexity of a flexible protein structure in solution, and a good agreement with experimental data is obtained: Frequencies from an experimental infrared (IR) spectrum are reproduced within 17 cm⁻¹ .     

A superionic state in nano-porous double-layer capacitors: insights from Monte Carlo simulations

Recently observed anomalous properties of ionic-liquid-based nanoporous supercapacitors [C. Largot et al., J. Am. Chem. Soc., 2008, 130, 2730-2731] have attracted much attention. Here we present Monte Carlo simulations of a model ionic liquid in slit-like metallic nanopores. We show that exponential screening of the electrostatic interactions of ions inside a pore, as well as the image-charge attraction of ions to the pore surface, lead to the 'anomalous' increase of the capacitance with decreasing the pore width. The simulation results are in good agreement with the experimental data. The capacitance as a function of voltage is almost constant for low voltages and vanishes above a certain threshold voltage. For very narrow pores, these two regions are separated by a peak. With increase of the pore size the peak turns into a bump and disappears for wide pores. This effect, related to a specific character of the voltage-induced filling of nanopores with counterions at high densities, is yet to be verified experimentally.     

Computation of methodology-independent ionic solvation free energies from molecular simulations. I. The electrostatic potential in molecular liquids

The computation of ionic solvation free energies from atomistic simulations is a surprisingly difficult problem that has found no satisfactory solution for more than 15 years. The reason is that the charging free energies evaluated from such simulations are affected by very large errors. One of these is related to the choice of a specific convention for summing up the contributions of solvent charges to the electrostatic potential in the ionic cavity, namely, on the basis of point charges within entire solvent molecules (M scheme) or on the basis of individual point charges (P scheme). The use of an inappropriate convention may lead to a charge-independent offset in the calculated potential, which depends on the details of the summation scheme, on the quadrupole-moment trace of the solvent molecule, and on the approximate form used to represent electrostatic interactions in the system. However, whether the M or P scheme (if any) represents the appropriate convention is still a matter of on-going debate. The goal of the present article is to settle this long-standing controversy by carefully analyzing (both analytically and numerically) the properties of the electrostatic potential in molecular liquids (and inside cavities within them). Restricting the discussion to real liquids of "spherical" solvent molecules (represented by a classical solvent model with a single van der Waals interaction site), it is concluded that (i) for Coulombic (or straight-cutoff truncated) electrostatic interactions, the M scheme is the appropriate way of calculating the electrostatic potential; (ii) for non-Coulombic interactions deriving from a continuously differentiable function, both M and P schemes generally deliver an incorrect result (for which an analytical correction must be applied); and (iii) finite-temperature effects, including intermolecular orientation correlations and a preferential orientational structure in the neighborhood of a liquid-vacuum interface, must be taken into account. Applications of these results to the computation methodology-independent ionic solvation free energies from molecular simulations will be the scope of a forthcoming article.     

Conductive,Stretchable,and Self-healing Ionic Gel Based on Dynamic Covalent Bonds and Electrostatic Interaction

Integrating multiple functions into one gel that can be widely applied to electronic devices as well as chemical and biomedical engineering remains a big challenge.Here,a multifunctional ionic liquid/dynamic covalent bonds (ionic/DCB) type gel was designed and synthesized via one-pot polymerization.With the assistance of electrostatic interaction provided by the imidazolium cations of IL and the reversible DCB of boronic ester,as-prepared ionic/DCB gel showed good stretchable properties and high ionic conductivity at ambient conditions.In addition,the electrostatic interaction between imidazolium cations and sulfonate anions and the reversible DCB led to enhanced chain mobility and thereby excellent self-healing properties.Particularly,sulfonate anions in ionic/DCB gel could alleviate the migration of electronegative polysulfide and promote the transportation of electropositive lithium ion in lithium-sulfur battery system.Therefore,this work provides a new insight to promote the current research on self-healing gels,hopefully expanding their applications in electronic devices.