Transport Properties Of Liquids Research Articles

Effects of Water Content on the Transport and Thermodynamic Properties of Phosphonium Ionic Liquids.

We present a numerical investigation of the influence of water content on the dynamic properties of a family of phosphonium-based room-temperature ionic liquids. The study presents a compelling correlation between structural changes in water-ionic liquid solutions and thermodynamic and transport properties across diverse systems. The results for phosphonium ionic liquids are compared with 1-butyl-3-methylimidazolium hexaphosphate ([bmim]PF6) as a reference. Through this approach, phosphonium cation structure-related characteristics can be identified and placed within the broader context of ionic liquids. These insights are underpinned by observed changes in interaction energy, boiling point, diffusion rate, and viscosity, highlighting the crucial role of water molecules in weakening the strength of interactions between ions within the ionic liquid. The investigation also explains temperature-dependent trends in phosphonium cations, showing that alkyl group length and molecular symmetry are important tuning parameters for the strength of Coulomb interactions. These results contribute to a refined understanding of phosphonium ionic liquid behavior in the presence of water, offering valuable insights for optimizing their use in diverse fields.

Viscosity of imidazolium ionic liquids and mixtures of ILs from entropy scaling using the PC-SAFT and ePC-SAFT equations of state

Entropy scaling is a promising method for the development of engineering models for transport properties of ionic liquids (ILs). Here we present two entropy scaling models for the viscosity of ionic liquids and their mixtures at various temperatures and pressures: 1) a molecular-based approach treating each IL as one pure species and using the PC-SAFT equation of state (EoS); and 2) treating each ion as a separate species and using the ePC-SAFT EoS. Both approaches were correlated to viscosity data of 12 ionic liquids from the imidazolium cation class and three different anions comprising 4233 data points with overall average absolute deviations (%AARDs) of less than 8 % over a wide range of temperature and pressures. The ion-based approach was better able to correlate IL viscosity at low temperatures and/or high pressure (to 4011 bar) than the molecular approach. The functional entropy-scaling coefficients for both models were regressed as linear functions of molecular weight, which allowed good prediction of another nine ionic liquids not in the training set. Interestingly, both approaches well predict the viscosity of binary mixtures of imidazolium ionic liquids. In addition, the effect of various reference viscosities and comparison with the Peng-Robinson EoS was performed.

Effect of Pore Confinement of Ionic Liquids on Solute Diffusion within Mesoporous Silica Microparticles.

The transport properties of the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) confined within silica microparticles with well-ordered, accessible mesopores (5.4 or 9 nm diameter) were investigated. [BMIM][PF6] confinement was confirmed by using differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. The transport properties of the confined IL were studied using the neutral and cationic fluorescent probes 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) and rhodamine 6G, respectively, through fluorescence recovery after photobleaching (FRAP) in confocal microscopy. The diffusivity of DCM in 9 nm pores is 0.026 ± 0.0091 μm2/s, which is 2 orders of magnitude less than in the bulk ionic liquid. The pore size did not affect the diffusivity of DCM in unmodified silica nanopores. The diffusivity of the cationic probe is reduced by 63% relative to that of the neutral probe. Diffusivity is increased with water content, where equilibrium hydration of the system leads to a 37% increase in DCM diffusivity. The most dramatic impact on diffusivity was caused by tethering an IL-like methylimidazolium chloride group to the pores, which increased the pore hydrophobicity and resulted in 3-fold higher diffusivity of DCM compared to bare silica pores. Subsequent exchange of the chloride anion from the tethering group with PF6- decreased the diffusivity to half that of bare silica. The diffusion of probe molecules is affected most strongly by the pore wall effects on probe interactions rather than by the pore size itself, which suggests that understanding pore wall diffusion is critical to the design of nanoconfined ILs for separations, catalysis, and energy storage.

Thermoresponsive Skin-like Fabric for Personal Comfort and Protection.

Acting as a "second skin", clothing plays an indispensable role in providing comfort and protection in the wide range of environments in which we live. However, comfort and protection are often competing requirements and are difficult to improve simultaneously. By mimicking the exceptional thermoresponsive one-way liquid transport property of human skin, here we developed a scalable and ecofriendly skin-like fabric that has a tunable directional water transport rate while having excellent water repellency. The water transport rate is also temperature-responsive, just like skin. As the temperature increases, the wettability gradient in the spatially distributed channels (acting like "sweat glands") increases, promoting sweat transport and evaporative heat dissipation. As the temperature decreases, on the other hand, the wettability gradient diminishes, reducing liquid transport and evaporative heat loss, thereby promoting heat retention. The fabric is highly suitable for sportswear and functional clothing and can have wider applications, such as oil-water separation, fog harvesting, etc.

Phonon thermal transport shaped by strong spin-phonon scattering in a Kitaev material Na2Co2TeO6

The report of a half-quantized thermal Hall effect and oscillatory structures in the magnetothermal conductivity in the Kitaev material α-RuCl3 have sparked a strong debate on whether it is generated by Majorana fermion edge currents, spinon Fermi surface, or whether other more conventional mechanisms are at its origin. Here, we report low temperature thermal conductivity (κ) of another candidate Kitaev material, Na2Co2TeO6. The application of a magnetic field (B) along different principal axes of the crystal reveals a strong directional-dependent B impact on κ, while no evidence for mobile quasiparticles except phonons can be concluded at any field. Instead, severely scattered phonon transport prevails across the B−T phase diagram, revealing cascades of phase transitions for all B directions. Our results thus cast doubt on recent proposals for significant itinerant magnetic excitations in Na2Co2TeO6, and emphasize the importance of discriminating true spin liquid transport properties from scattered phonons in candidate materials.

Multi-inspired Janus fabrics with asymmetric coolmax patterns for rapid sweat diffusion and effective sweat-shedding

Janus fabrics with unidirectional liquid transport property have attracted wide attention for their ability to remove excess sweat and lower skin temperature. However, most Janus fabrics face the sweat removal issue on their outer surface when the sweat absorption capacity of their hydrophilic surface reaches limit, which inevitably slows down one-way sweat transport rate and induces the fabrics to become heavy/clingy. Herein, inspired by natural Namib Desert beetles and drip tips, circular Coolmax patterns (severed as sweat extraction points near the skin) and triangular Coolmax patterns (severed as sweat removal zones on the outside of the fabric) are asymmetrically sewn on superhydrophobic cotton fabrics to enable continues one-way sweat transport and allow effective sweat diffusion/shedding on its outer surface. During the sweat transporting and evaporation process, a large amount of heat is dissipated. As a result, the created Janus fabrics can maintain human body temperature about 1.3 ℃ lower than the conventional cotton fabric. Moreover, the low adhesion (∼0.2 mN cm−2) between the wet skin and the fabric makes wearers feel more comfortable. The method can be potentially used for the large-scale commercial production of Janus fabrics and provide insights for the development of smart fabrics in the future.

Soot formation in combustion of spherically symmetric isolated fuel droplets with different initial diameters

Spherically-symmetric, isolated droplets are ideal systems to investigate the physics and the chemistry of combustion of liquid fuels. Despite their simplicity, most phenomena involved in spray combustion are still accounted for: evaporation and diffusion-induced transport, complex liquid thermodynamics, radiation, aerosol chemistry. In this work we analyzed the formation and evolution of soot particles and aggregates from the combustion of n-heptane isolated droplets. A 1D mathematical model including detailed description of thermodynamics and transport properties of liquid and gaseous phases, radiative heat transfer, and detailed homogeneous chemistry is adopted. Soot formation and evolution is described via a discrete sectional method, accounting for nucleation, surface growth, coagulation, aggregation, and oxidation.The mathematical model was utilized in this study to investigate how the initial diameter of droplets affects their tendency to form soot. The simulations were specifically designed to examine the experimental findings of Choi et al. (2001), which indicated that droplets with intermediate diameters (∼ 1.9 mm) result in the highest soot volume fraction. The numerical results reveal that this maximum is due to a competition between two phenomena: (i) increasing droplet diameter leads to a longer lifetime, thereby promoting soot formation, but (ii) larger diameters cause more radiative losses, lower flame temperatures, and subsequently, a decrease in soot formation.

Phase Equilibrium and Transport Properties of the Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)amide and Compressed Difluoromethane and Pentafluoroethane

Phase Equilibrium and Transport Properties of the Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)amide and Compressed Difluoromethane and Pentafluoroethane

Impact of fluorination on Li+ solvation and dynamics in ionic liquid-hydrofluoroether locally concentrated electrolytes

The thermal, physical, structural, and transport properties of ionic liquid (IL) electrolytes based on n-methyl-n-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide [PYR14][TFSI] and Li-salts of lithium (nonafluorobutane)(trifluoromethanesulfonyl)imide [Li][IM14] and [Li][TFSI] (0 ≤ xLi ≤ 0.3), with addition of 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) (0 ≤ xTTE ≤ 0.45) were studied. While [IM14] increases glass transition, TTE improves conductivity over a wider liquidus range. Li+ is solvated primarily by [TFSI] with some contribution by [IM14]. However, both 7Li- 19F HOESY NMR and spatial distribution functions (SDFs) derived from molecular dynamics (MD) indicate short contacts between the fluorines of TTE and Li+. This is a result of tighter anion-solvated Li+ without aggregation of the Li+ solvates, consistent with Raman measurements, thus confirming the existence of fluorous domains in the bulk which leads to improved fluidity and a Li+ diffusivity of 1.26 × 10−12 m2/s at 0 °C (xLi = 0.20) with a Li+ transference of 0.16. Improved transport properties translated to a higher capacity of the TTE/IL electrolyte in a Li||LiFePO4 half-cell with 95mAh/g at 0.1C, compared to the IL electrolyte without TTE (60 mAh/g). This study demonstrates the tunability of solvation and transport properties in IL electrolytes by asymmetric fluorinated anions and hydrofluoroether co-solvents for low temperature Li-ion batteries.

Next Generation Fluorine-Free Proton Exchange Membranes for Electrochemical Energy Applications

Most commercially available proton exchange membrane (PEM)-based fuel cell and electrolyser systems currently employ perfluorinated sulfonic acid (PFSA)-based PEMs, e.g., Nafion. The use of these fluorinated polymers presents serious health and environmental concerns as their production, degradation, and disposal results in the release of hazardous perfluorinted compounds that have been shown to accumulate in the environment and are toxic to living organisms.[1] Developing non-toxic, safe-by-design hydrocarbon PEMs is therefore crucial to ensure that renewable technologies that rely on proton exchange membranes remain an environmentally friendly solution. Additional shortcomings of PFSA-based PEMs include their expensive synthetic cost, inherently high hydrogen crossover, and limited operating temperature range due to poor thermo-mechanical properties above 90 °C. Hydrocarbon (HC)-based membranes offer advantages over their perfluorinated counterparts in these specific areas, however, the main drawback of HC-PEMs is that they require a much greater density of sulfonic acid groups to achieve similar proton conductivities as PFSA-based polymers.[2] This leads to greater water uptake and excessive swelling which ultimately leads to reduced mechanical stability of HC membranes.More recently there has been an increasing number of reports exploring the use of block copolymer strategies to limit the water uptake and swelling properties of hydrocarbon PEMs while maintaining good ionic conductivity.[3] As the ion, liquid, and gas transport properties of the membrane are largely attributed to the hydrophilic blocks (i.e., with sulfonic acid groups) and the mechanical, chemical, and thermal stability of the resulting membrane is determined by the hydrophobic blocks (i.e., no sulfonic acid groups), it is postulated that the resulting membrane properties can be tuned by varying the fraction of hydrophilic/hydrophobic blocks.The overall goal of this project is to synthesise hydrocarbon block copolymer PEMs with reduced gas crossover and enhanced the mechanical properties while maintaining sufficiently high ionic conductivity, ultimately leading to higher performance and greater durability inelectrochemical energy conversion and storage systems, e.g., fuel cells and electrolysers. In this project we have compared the ex-situ properties of novel hydrocarbon block copolymers with PFSA-based Nafion membranes, e.g., water uptake and swelling, conductivity measurements, oxidative stability via Fenton's test, etc., as well as in-situ performance tests in single cell fuel cell and electroylzers.[1]Feng, M.; Wang, Z. et al. Sci. Rep. 2015, 5, 9859.[2]Holdcroft, S. Chem. Mater. 2014, 26, 381.[3]Guiver, M. et al. Chem. Rev. 2017, 117, 4759.

Heterogeneous-elasticity theory of instantaneous normal modes in liquids

Since decades, the concept of vibrational density of states in glasses has been mirrored in liquids by the instantaneous-normal-mode spectrum. In glasses instantaneous configurations are believed to be situated close to minima of the potential-energy hypersurface and all eigenvalues of the associated Hessian matrix are positive. In liquids this is no longer true, and modes corresponding to both positive and negative eigenvalues exist. The instantaneous-normal-mode spectrum has been numerically investigated in the past, and it has been demonstrated to bring important information on the liquid dynamics and transport properties. A systematic deeper theoretical understanding is now needed. Heterogeneous-elasticity theory has proven to be particularly successful in explaining many details of the low-frequency excitations in glasses, ranging from the thoroughly studied boson peak, to other anomalies related to the crossover between wave-like and random-matrix-like excitations. Here we present an extension of heterogeneous-elasticity theory to the liquid state, and show that the outcome of the theory agrees well to the results of extensive molecular-dynamics simulations of a model liquid at different temperatures. We find that the spectrum of eigenvalues ρ(λ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho (\\lambda )$$\\end{document} has a sharp maximum close to (but not at) λ=0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda =0$$\\end{document}, and decreases monotonically with |λ|\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$|\\lambda |$$\\end{document} on both its stable and unstable side. We show that the spectral shape strongly depends on temperature, being symmetric at high temperatures and becoming rather asymmetric at low temperatures, close to the dynamical critical temperature. Most importantly, we demonstrate that the theory naturally reproduces a surprising phenomenon, a zero-energy spectral singularity with a cusp-like character developing in the vibrational spectra upon cooling. This feature, known from a few previous numerical studies, has been generally overlooked in the past due to a misleading representation of the data. We provide a thorough analysis of this issue, based on both very accurate predictions of our theory, and computational studies of model liquid systems with extended size.

Unveiling the transport properties of protic ionic liquids: Lithium ion dynamics modulated by the anion fluorine reservoir

Protic ionic liquids (PILs) show great potential as electrolyte components for energy storage devices. A comprehensive understanding of their transport properties must be achieved to optimize the design of safer and efficient electrolytes. This study focuses on a series of PILs based on the DBUH+ cation (protonated 1,8-diazabicyclo[5,4,0]‑undec-7-ene superbase) and three anions derived from strong acids: TFO− (triflate), IM14− (perfluorobutyl-trifluoromethylsulfonylimide) and TFSI− (bis(trifluoromethylsulfonyl)imide). Neat PILs and PILs doped with LiTFO, LiIM14, and LiTFSI were studied using temperature-dependent NMR diffusion and relaxation techniques. The ionicity of these systems was also evaluated. Results revealed that the dynamic behaviour of lithium ions, as well as ionicity, strongly depend on the structural features of the anions, particularly in the case of IM14−, whose main feature is the uneven distribution of the fluorinated sidegroups. The 19F relaxation rates in IM14− provide insights into the rotational reorientation of that anion. DBUH-IM14 exhibited diffusion coefficients lower than the expected ones on the basis of its viscosity, likely due to fluorophilic intermolecular interactions involving the fluorinated terminal groups. The presence of Li+ in the DBUH-IM14 electrolyte led to unexpected and relatively faster translational mobility of Li+ ions, resulting in a higher lithium apparent transference number. However, the trends observed in ionicity indicate a more complex interplay between intermolecular interactions and ion correlations. While DBUH-TFSI showed minimal effect of Li+ addition, DBUH-TFO and DBUH-IM14 exhibited a significant decrease in ionicity, possibly attributed to strong interactions between ions.

Dual liquid-assisted single-layered Janus mesh membrane with controllable and efficient directional water transport for multiple applications

Janus porous membranes with anisotropic interfaces exhibiting directional liquid transport properties have emerged as important tools for addressing real-world issues, such as oil-spill cleanup and fog collection. Here, a single-layered Janus mesh membrane with asymmetric wettability and a well-tuned hydrophilization depth is prepared using an ethanol-assisted floating method. Consequently, the well-regulated hydrophilization depth combined with a water-assisted strategy achieves controllable and efficient directional water transport properties, which also gives rise to a high anisotropic critical breakthrough pressure. In addition, the water-assisted controllability can form an on–off gate capable of allowing or blocking water to pass through upon request. Moreover, we theoretically and experimentally determine the changeable contact area as important in directional water transport properties. Controllable directional water transport behavior with a high pressure difference has been demonstrated in on-demand oil–water separation and intravenous infusion, whereas the efficient directional water transport properties have potential applications in fog collection. Overall, this work provides a new idea for the preparation of a single-layered multifunctional Janus mesh membrane with a high anisotropic critical breakthrough pressure and opens an avenue for controllable and efficient directional water transport properties for diverse applications.

Molecular dynamic study on the transport properties of ionic liquids in ZTC porous carbon materials

The adsorption and diffusion behavior of ions within electrodes have a significant impact on the energy density and charging/discharging speed of supercapacitors. Zeolite-Templated Carbon (ZTC) material, a type of porous carbon material characterized by well-defined pore shape and spatial structure, is recognized as a promising electrode material owing to its numerous advantages. This study employs molecular dynamics simulations to investigate the diffusion and adsorption profiles of ionic liquids [EMI][BF4] in different types of ZTC materials as electrodes. Additionally, the effect of ion size, pore dimension, pore shape, and the properties of the adsorbed ions are discussed. The degree of confinement (DOC) and ion diffusivity are thoroughly analyzed to elucidate the transport behavior of ions within the ZTC pores. The results demonstrate that the diffusion coefficient and degree of confinement of ionic liquids predominantly depend on the anion size and the pore size of the porous carbon. Surprisingly, in certain cases, larger anions exhibit enhanced diffusion ability and adsorption effect. These findings unravel the underlying transport mechanism of ions in ZTC materials and provide valuable theoretical insights for the application of ZTC materials as electrodes in the field of supercapacitors.

Preparation and characterization of bio-inspired full-biomass-derived aerogel with vertically aligned structure

Using renewable biomass resources to prepare porous materials can reduce the dependence on petroleum-based energy, promote green, low-carbon, and high-quality development, and achieve carbon neutrality. Here, we report a bio-inspired full-biomass-derived aerogel with an ultra-light (10.33–27.77 mg/cm3), highly porous (98.66–99.19 %), and vertically aligned structure. The fabrication involves an ultrasonic-assisted deep eutectic solvent (DES) extraction of cellulose nanofibrils (CNFs)-blending-directional freeze-drying-hydrophobic modification. Initially, CNFs were extracted from corncobs using DES pretreatment. Then, the aerogels were prepared by co-mixing CNFs with alkali lignin and freeze-drying the precursor suspension using the ice-templated method. Finally, the aerogels were modified using trimethoxymethylsilane chemical vapor deposition to render them hydrophobic. The silanization-modified aerogels exhibited superior static and dynamic hydrophobic properties, with a water contact angle of up to 153.4°, and demonstrated self-cleaning properties. These aerogels exhibited adsorption capabilities for various oils and organic solvents (9.6–29.8 g/g) and the ability to separate oil–water mixtures and adsorb methylene blue. Moreover, the aerogels with vertically aligned structures exhibited exceptional axial compression properties (up to 959 kPa), more than four times greater than the radial compression properties. Furthermore, the aerogels exhibited rapid liquid transport properties, with an axial transport rate of soybean oil that was more than 10 times higher than the radial transport rate. This study provides a green, eco-friendly, and sustainable strategy for preparing 3D porous aerogels, paving the way for developing full-biomass-derived aerogels as a promising alternative to petroleum-based adsorbent materials.

Surface engineered long-lasting antibacterial Janus cotton fabrics with excellent moisture/thermal management properties

The hydrophilic property of traditional cotton fabrics invariably facilitates sweat absorption, potentially leading to discomfort such as cold and clammy sensation, and even promoting bacterial proliferation. Herein, we developed a Janus cotton fabric using a surface engineering strategy combining “graft through” and “mist polymerization” methodologies. Through the “graft through” polymerization of methacryloyloxyethyl dodecyl dimethyl ammonium bromide (DMDB), we constructed a well-designed antibacterial coating on the fabric with amphiphilic properties. The resulting polymer, PDMDB, imparts highly efficient and durable antibacterial properties to the cotton fabric, achieving a bcteriostatic rates against S. aureus and E. coli of > 99.9 %. Even after undergoing 150 washing cycles, the residual bactericidal efficacy remains above 99 %. Additionally, the reversible hydrophilic-hydrophobic nature of PDMDB successfully enables the construction of a Janus structure on cotton fabrics via “mist polymerization”. Benefiting from its comprehensive design, the Janus cotton fabrics realize a superior directional liquid transport property. Its water evaporation rate is 1.3–1.5 times higher than that of the original cotton fabric in continuous outdoor moisture management, while maintaining body temperature 5.63 °C lower than that of the surrounding environment. It is worth mentioning that our approach utilizes abundant raw materials and facile modification technologies, thereby providing a favorable guarantee for the mass production and use of Janus cotton fabrics.

Transport properties of imidazolium-based room temperature ionic liquids in confinement of slit charged carbon nanopores: New insights from molecular simulations

The paper presents a study of the behavior of room-temperature ionic liquids with different alkyl chain lengths and anion types in slit negatively charged carbon nanopores of various widths (1–15 nm) using all-atom molecular dynamics simulations. The structure of the confined ionic liquids is investigated using number, mass, and charge density profiles and radial distribution functions. The paper also discusses such characteristics as mean squared displacement of ions in all directions, self-diffusion coefficients of cations and anions in the bulk, their temperature dependences, electrical conductivity. Some energy characteristics are obtained by quantum chemical calculations. It is established that there is a bulk region in the pore center for all the confined ionic liquids, starting from the pore width of 7 nm. The sums of the cationic and anionic self-diffusion coefficients of different ionic liquids can be arranged as follows: D[OMIM][BF4] < D[EMIM][BF4] < D[OMIM][NTf2] < D[EMIM][NTf2]. Due to layering structure inside the pore, the dynamics of the ions is heterogeneous. It is shown that the RTILs with longer alkyl chains have lower electrical conductivities regardless of temperature. The opposite effect associated with the species size is observed for RTILs with different anions.

Molecular simulations of transport properties of polar hydrofluoroethers: Force field development, fractional Stokes-Einstein and free volume relations

Hydrofluoroethers (HFEs) having simultaneously hydrocarbon (HC) and fluorocarbon (FC) moieties connected through ether oxygen are polar chain molecules with dielectric properties, which makes them a good heat transfer medium, e.g., for cooling of electronics or magnetic devices. In this work, we report, validate, and test high level-ab initio derived force fields and we use partial charges fitted to the electrostatic potential surface (EPS) to reproduce the dipole moments. Computer simulations were performed over a wide range of temperatures and densities to calculate the transport coefficients in the condensed-phase and comparisons were made against available experimental data for five selected molecules; namely HFE-7000, HFE-7100, HFE −7200, HFE −7300, and HFE −7500. Furthermore, structural properties and enthalpy of vaporization were obtained from molecular simulations. Cohen and Turnbull formula for the translational self-diffusion coefficient was tested in the free-volume cast, which itself was correlated against the isothermal compressibility, which can explain the phenomenon of transport properties in liquids, D∝exp-γ/Vf/V∗. The fractional Stokes-Einstein relation was also tested to scale the self-diffusion coefficient vs viscosity in the form of (DT−1) ∝ (1/η)s, with s ranging between ≈ 0.89 and 0.92 for the five molecules in the reduced density range of ρσ3 = 0.56 to 0.75. Finally, the non-equilibrium molecular dynamics (NEMD) simulations of thermal conductivity was found to outperform the equilibrium Green-Kubo approach, but both with comparable accuracy.

Multi-bioinspired Janus-shedding fabric: One-way sweat transport and rapid sweat removal for improved personal moisture management

In recent years, Janus fabrics that can effectively facilitate personal moisture management have received great attention. However, they are still limited in sweat shedding issue of their superhydrophilic outer surface. Here, inspired by the lotus leaf and Namib Desert beetles, we propose a Janus-shedding fabric with superhydrophilic/hydrophobic patterns and asymmetric wetting property. Through femtosecond-laser microfabrication, we successfully construct superhydrophilic/hydrophobic patterns on the outside surface of Janus fabrics. The method prevents the usage of toxic chemical reagent, thus is completely environmentally-friendly. The as-prepared Janus-shedding fabrics possess one-way liquid transport property. More importantly, the fabrics can achieve rapid liquid/sweat removal on their hydrophilic outer surfaces. The liquid shedding mechanism can be explained that the hydrophilic/hydrophobic patterns on the outer fabric surface can create less surface tension of water which can only fix small volume of water. Moreover, they can maintain human body temperature 3.2 ℃ lower than covered with pristine cotton fabrics. This work provides new insights for the design and fabrication of advanced smart fabrics with both sweat transport and removal property for satisfying the growing demands of personal comfort.

Elucidation of Liquid Structures and Transport Properties of Highly Concentrated LiN(SO2F)2/Ethylene Carbonate Electrolytes

The Li+ conduction mechanism in highly concentrated ethylene carbonate (EC) solution of lithium bis(fluorosulfonyl)amide (LiFSA) was studied based on the measurements of thermal properties, density, viscosity, ionic conductivity, self-diffusion coefficients, Raman spectra, and proton nuclear magnetic resonance relaxation time. The compositions of EC and LiFSA were varied from dilute to concentrated states ([EC]/[LiFSA] = 9.2–0.80). For compositions of [EC]/[LiFSA] ≤ 1.5, the free solvents decrease, and contact ion pairs and aggregates become dominant, causing a significant change in the transport properties. Faster diffusion of Li+ compared with solvent (Li+ hopping conduction) was observed when the molar composition of [EC]/[LiFSA] ≤ 1.0 as in the case of sulfolane.