Ideality of liquid structure: A case study for metallic alloy liquids
Abstract not provided
Ryu, Chae Woo↗
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Self-Assembly of MXene-Surfactants at Liquid–Liquid Interfaces: From Structured Liquids to 3D Aerogels
2D transition metal carbides and nitrides (MXenes), a class of emerging nanomaterials with intriguing properties, have attracted significant attention in recent years. However, owing to the highly hydrophilic nature of MXene nanosheets, assembly strategies of MXene at liquid-liquid interfaces have been very limited and challenging. Here in this paper, through the cooperative assembly of MXene and amine-functionalized polyhedral oligomeric silsesquioxane at the oil-water interface, we report the formation, assembly, and jamming of a new type MXene-based Janus-like nanoparticle surfactants, termed MXene-surfactants (MXSs), which can significantly enhance the interfacial activity of MXene nanosheets. More importantly, this simple assembly strategy opens a new platform for the fabrication of functional MXene assemblies from mesoscale (e.g., structured liquids) to macroscale (e.g., aerogels), that can be used for a range of applications, including nanocomposites, electronic devices, and all-liquid microfluidic devices.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Nanoparticle surfactants and structured liquids
Materials are usually classified as solids or liquids, based on their structural stability, dynamic response, and rheological properties. Structured liquid, a new state of matter, has attracted much attention in recent years. Different with either solid or liquid, structured liquid combines the desirable characteristics of fluids with the structural stability of a solid, showing a myriad of potential applications in encapsulation, biphasic reactors, and programmable liquid constructs. Here, a brief review is given, by introducing a new strategy to structure liquids based on the formation, assembly, and jamming of nanoparticle surfactants (NPSs) at liquid-liquid interfaces. Furthermore, the interfacial packing of the NPSs can be effectively manipulated using external triggers, endowing the structured liquids with adaptiveness and responsiveness to changes in their external environment.
36 MATERIALS SCIENCE↗
Curie-Weiss behavior of liquid structure and ideal glass state
We present the results of a structural study of metallic alloy liquids from high temperature through the glass transition. We use high energy X-ray scattering and electro-static levitation in combination with molecular dynamics simulation and show that the height of the first peak of the structure function, S(Q) -1, follows the Curie-Weiss law. The structural coherence length is proportional to the height of the first peak, and we suggest that its increase with cooling may be related to the rapid increase in viscosity. The Curie temperature is negative, implying an analogy with spin-glass. The Curie-Weiss behavior provides a pathway to an ideal glass state, a state with long-range correlation without lattice periodicity, which is characterized by highly diverse local structures, reminiscent of spin-glass.
36 MATERIALS SCIENCE↗
Nanoscale Perturbations of Room Temperature Ionic Liquid Structure at Charged and Uncharged Interfaces
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catalysis (heterogeneous)↗
Molecular Brush Surfactants: Versatile Emulsifiers for Stabilizing and Structuring Liquids
Using amphiphilic molecular brushes to stabilize emulsions usually requires the synthesis of specific side chains, which can be a time-consuming and difficult challenge to meet. By taking advantage of the electrostatic interactions between water-soluble molecular brushes and oil-soluble oligomeric ligands, here the in situ formation, assembly and jamming of molecular brush surfactants (MBSs) at the oil-water interface is described. With MBSs, stable emulsions including o/w, w/o and o/w/o can be easily prepared by varying the molar ratios of the molecular brushes to the ligands. Moreover, when jammed, the binding energy of MBSs at the interface is sufficiently strong to allow the stabilization of liquids in nonequilibrium shapes, i.e., structuring liquids, producing an elastic film at the interface with exceptional mechanical properties. These structured liquids have numerous potential applications, including chemical biphasic reactions, liquid electronics, and all-liquid biomimetic system.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Mixtures of octanol and an ionic liquid: Structure and transport
Ionic liquids (ILs) with long alkyl substituents are amphiphilic, which leads to a bicontinuous liquid structure. The strongly interacting anionic and cationic head groups form a long range charge network, with the hydrocarbon tails forming a nonpolar domain. Such nonpolar domains have been shown to dissolve a variety of neutral organic solvents. In mixtures of ILs with solvents the neutral organic molecules residing in the nonpolar domains experience different environments and friction from the charged cations and anions. Thus, the neutral molecules diffuse much faster than predicted by hydrodynamic scaling using the average viscosity of the mixture. Here, we report studies on the structure and transport properties of mixtures of 1-octanol with the IL trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide (P 6,6,6,14 + /NTf 2 – ). The majority of the atom fraction in the P 6,6,6,14 + cation comprises four hydrocarbon substituents. The unique amphiphilic nature of ILs with the P 6,6,6,14 + cation makes 1-octanol fully miscible with the IL at ambient temperatures. X-ray scattering experiments show that the IL structure persists in the mixtures for 1-octanol mole fractions as large as x oct = 0.90. The self-diffusion coefficients of the three molecular species in the mixtures were measured by NMR experiments. The self-diffusion of the P 6,6,6,14 + cation is well described by the Stokes–Einstein equation, while the diffusivity of the NTf 2 – anion is slightly lower than the hydrodynamic prediction. The measured diffusivities of octanol in these mixtures are 1.3–4 times higher than the hydrodynamic predictions.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Ab initio and force field molecular dynamics study of bulk organophosphorus and organochlorine liquid structures
Here, we performed ab initio molecular dynamics (AIMD) simulations to benchmark bulk liquid structures and to evaluate results from all-atom force field molecular dynamics (FFMD) simulations with the generalized Amber force field (GAFF) for organophosphorus (OP) and organochlorine (OC) compounds. Our work also addresses the current and important topic of force field validation, applied here to a set of nonaqueous organic liquids. Our approach differs from standard treatments, which validate force fields based on thermodynamic data. Utilizing radial distribution functions (RDFs), our results show that GAFF reproduces the AIMD-predicted asymmetric liquid structures moderately well for OP compounds that contain bulky alkyl groups. Among the OCs, RDFs obtained from FFMD overlap well with AIMD results, with some offsets in position and peak structuring. However, re-parameterization of GAFF for some OCs is needed to reproduce fully the liquid structures predicted by AIMD. The offsets between AIMD and FFMD peak positions suggest inconsistencies in the developed force fields, but, in general, GAFF is able to capture short-ranged and long-ranged interactions of OPs and OCs observed in AIMD. Along with the local coordination structure, we also compared enthalpies of vaporization. Overall, calculated bulk properties from FFMD compared reasonably well with experimental values, suggesting that small improvements within the FF should focus on parameters that adjust the bulk liquid structures of these compounds.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Molecular Brush Surfactants: Versatile Emulsifiers for Stabilizing and Structuring Liquids
Abstract Using amphiphilic molecular brushes to stabilize emulsions usually requires the synthesis of specific side chains, which can be a time‐consuming and difficult challenge to meet. By taking advantage of the electrostatic interactions between water‐soluble molecular brushes and oil‐soluble oligomeric ligands, the in situ formation, assembly and jamming of molecular brush surfactants (MBSs) at the oil‐water interface is described. With MBSs, stable emulsions including o/w, w/o and o/w/o can be easily prepared by varying the molar ratios of the molecular brushes to the ligands. Moreover, when jammed, the binding energy of MBSs at the interface is sufficiently strong to allow the stabilization of liquids in nonequilibrium shapes, i.e., structuring liquids, producing an elastic film at the interface with exceptional mechanical properties. These structured liquids have numerous potential applications, including chemical biphasic reactions, liquid electronics, and all‐liquid biomimetic system.
Wang, Beibei↗
Liquid Structure of CO 2 –Reactive Aprotic Heterocyclic Anion Ionic Liquids from X-ray Scattering and Molecular Dynamics
A combination of X-ray scattering experiments and molecular dynamics simulations were conducted to investigate the structure of ionic liquids (ILs) which chemically bind CO 2 . The structure functions were measured and computed for four different ILs consisting of two different phosphonium cations, triethyloctylphosphonium ([P 2228 ] + ) and trihexyltetradecylphosphonium ([P 66614 ] + ), paired with two different aprotic heterocyclic anions which chemically react with CO 2 , 2-cyanopyrrolide, and 1,2,4-triazolide. Simulations were able to reproduce the experimental structure functions, and by deconstructing the simulated structure functions, further information on the liquid structure was obtained. All structure functions of the ILs studied had three primary features which have been seen before in other ILs: a prepeak near 0.3–0.4 Å–1 corresponding to polar/nonpolar domain alternation, a charge alternation peak near 0.8 Å–1, and a peak near 1.5 Å–1 due to interactions of adjacent molecules. The liquid structure functions were only mildly sensitive to the specific anion and whether or not they were reacted with CO 2 . Upon reacting with CO 2 , small changes were observed in the structure functions of the [P 2228 ] + ILs, whereas virtually no change was observed upon reacting with CO 2 in the corresponding [P 66614 ] + ILs. When the [P 2228 ] + cation was replaced with the [P 66614 ] + cation, there was a significant increase in the intensities of the prepeak and adjacency interaction peak. While many of the liquid structure functions are similar, the actual liquid structures differ as demonstrated by computed spatial distribution functions.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Liquid structure of dibutyl sulfoxide
We present experimental (x-ray diffraction) data on the structure of liquid dibutyl sulfoxide at 320 K and rationalize them by means of Molecular Dynamics simulations. Not unexpectedly, DBSO bearing a strong dipolar moiety and two medium length, apolar, butyl chains, this compound turns out to be characterised by a distinct degree of polar-vs-apolar structural differentiation at the nm spatial scale that is fingerprinted in a low Q peak in its x-ray diffraction pattern. Similarly to, but to a larger extent than its shorter chain family members (such as DMSO), DBSO is also characterised by an enhanced dipole-dipole correlation that is responsible for the moderate Kirkwood correlation factor as well as for the self-association detected in this compound. In conclusion, we show however that the supposedly relevant hydrogen bonding correlations between oxygen and butyl chain hydrogens are of limited extent and only in the case of α-hydrogens appreciable indication of the existence of such an interaction is found, but it turns out to be a mere consequence of the strong dipole-dipole correlation.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Dependence of solid-liquid interface free energy on liquid structure
The Turnbull relation is widely believed to enable prediction of solid–liquid interface (SLI) free energies from measurements of the latent heat and the solid density. Ewing proposed an additional contribution to the SLI free energy to account for variations in liquid structure near the interface. In the present study, molecular dynamics (MD) simulations were performed to investigate whether SLI free energy depends on liquid structure. Analysis of the MD simulation data for 11 fcc metals demonstrated that the Turnbull relation is only a rough approximation for highly ordered liquids, whereas much better agreement is observed with Ewing’s theory. A modification to Ewing’s relation is proposed in this study that was found to provide excellent agreement with MD simulation data.
36 MATERIALS SCIENCE↗
Chemistry, applications, and future prospects of structured liquids
This review article centers around structured liquids and their underlying mechanisms. The focus is on the chemistry, applications, characterization, reconfigurability, and future prospects of this class of soft materials.
Ghaffarkhah, Ahmadreza↗
Liquid structure and temperature invariance of sound velocity in supercooled Bi melt
Structural rearrangement of liquid Bi in the vicinity of the melting point has been proposed due to the unique temperature invariant sound velocity observed above the melting temperature, the low symmetry of Bi in the solid phase and the necessity of overheating to achieve supercooling. The existence of this structural rearrangement is examined by measurements on supercooled Bi. The sound velocity of liquid Bi was measured into the supercooled region to high accuracy and it was found to be invariant over a temperature range of ∼60°, from 35° above the melting point to ∼25° into the supercooled region. The structural origin of this phenomenon was explored by neutron diffraction structural measurements in the supercooled temperature range. These measurements indicate a continuous modification of the short range order in the melt. The structure of the liquid is analyzed within a quasi-crystalline model and is found to evolve continuously, similar to other known liquid pnictide systems. The results are discussed in the context of two competing hypotheses proposed to explain properties of liquid Bi near the melting: (i) liquid bismuth undergoes a structural rearrangement slightly above melting and (ii) liquid Bi exhibits a broad maximum in the sound velocity located incidentally at the melting temperature.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Functional Janus structured liquids and aerogels
Janus structures have unique properties due to their distinct functionalities on opposing faces, but have yet to be realized with flowing liquids. We demonstrate such Janus liquids with a customizable distribution of nanoparticles (NPs) throughout their structures by joining two aqueous streams of NP dispersions in an apolar liquid. Using this anisotropic integration platform, different magnetic, conductive, or non-responsive NPs can be spatially confined to opposite sides of the original interface using magnetic graphene oxide (mGO)/GO, Ti 3 C 2 T x /GO, or GO suspensions. The resultant Janus liquids can be used as templates for versatile, responsive, and mechanically robust aerogels suitable for piezoresistive sensing, human motion monitoring, and electromagnetic interference (EMI) shielding with a tuned absorption mechanism. The EMI shields outperform their current counterparts in terms of wave absorption, i.e., SE T ≈ 51 dB, SE R ≈ 0.4 dB, and A = 0.91, due to their high porosity ranging from micro- to macro-scales along with non-interfering magnetic and conductive networks imparted by the Janus architecture.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Carbon dioxide in an ionic liquid: Structural and rotational dynamics
Ionic liquids (ILs), which have widely tunable structural motifs and intermolecular interactions with solutes, have been proposed as possible carbon capture media. In order to inform the choice of an optimal ionic liquid system, it can be useful to understand the details of dynamics and interactions on fundamental time scales (femtoseconds to picoseconds) of dissolved gases, particularly carbon dioxide (CO 2 ), within the complex solvation structures present in these uniquely organized materials. The rotational and local structural fluctuation dynamics of CO 2 in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2) were investigated by using ultrafast infrared spectroscopy to interrogate the CO 2 asymmetric stretch. Polarization-selective pump probe measurements yielded the orientational correlation function of the CO 2 vibrational transition dipole. It was found that reorientation of the carbon dioxide occurs on 3 time scales: 0.91 ± 0.03, 8.3 ± 0.1, 54 ± 1 ps. The initial two are attributed to restricted wobbling motions originating from a gating of CO 2 motions by the IL cations and anions. The final (slowest) decay corresponds to complete orientational randomization. Two-dimensional infrared vibrational echo (2D IR) spectroscopy provided information on structural rearrangements, which cause spectral diffusion, through the time dependence of the 2D line shape. Analysis of the time-dependent 2D IR spectra yields the frequency-frequency correlation function (FFCF). Polarization-selective 2D IR experiments conducted on the CO 2 asymmetric stretch in the parallel- and perpendicular-pumped geometries yield significantly different FFCFs due to a phenomenon known as reorientation-induced spectral diffusion (RISD), revealing strong vector interactions with the liquid structures that evolve slowly on the (independently measured) rotation time scales. To separate the RISD contribution to the FFCF from the structural spectral diffusion contribution, the previously developed first order Stark effect RISD model is reformulated to describe the second order (quadratic) Stark effect—the first order Stark effect vanishes because CO 2 does not have a permanent dipole moment. Through this analysis, we characterize the structural fluctuations of CO 2 in the ionic liquid solvation environment, which separate into magnitude-only and combined magnitude and directional correlations of the liquid’s time dependent electric field. This new methodology will enable highly incisive comparisons between CO 2 dynamics in a variety of ionic liquid systems.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Repairable and Reconfigurable Structured Liquid Circuits
The advance of printed electronics is significantly bolstered by the development of liquid-state electronics that overcome the inherent limitations in flexibility and reconfigurability of solid-state electronics. By integrating the biocompatibility and conductivity of sulfonated polyaniline (S-PANI) and phytic acid (PA) with the reconfigurability of structured liquids, highly conductive all-liquid threads are developed. The dense packing and overlap of PA/S-PANI complexes at an oil/water interface promotes in-plane electron transport, and standard four-point probe measurements of PA/S-PANI interfacial assemblies demonstrate enhanced electrical properties. Notably, the rapid jetting of the ink phase into the matrix phase allows for liquid threads to be printed, enabling the fabrication of large-scale, conductive pathways between two electrodes and liquid circuits. Upon mechanical cleavage of the liquid wires, circuits can be broken, but will easily self-repair using an electric field, making this motif useful in the design of switches as well as restoring conductive pathways in series or in parallel. In conclusion, the demonstrated flexibility and reconfigurability these PA/S-PANI wires possess hold significant promise for their practical use in the design of flexible and adaptive bioelectronics that can be repaired on demand, signifying a transformative step in the evolution of liquid electronic materials.
36 MATERIALS SCIENCE↗
Photoresponsive Structured Liquids Enabled by Molecular Recognition at Liquid–Liquid Interfaces
Using host-guest molecular recognition at the oil-water interface, a new type of photoresponsive nanoparticle surfactant (NPS) was designed and prepared to structure liquids. With the help of a polymeric surfactant, the interfacial host-guest interactions can be significantly enhanced, leading to the rapid formation and assembly of a NP monolayer and offering sufficient binding energy to hold the NPs in a jammed state. The assembly of the NPSs can be reversibly manipulated via a photoswitchable jamming-to-unjamming transition, endowing the interface as well as the macroscopic assemblies with responsiveness to the external trigger (photons). Finally, this study for the first time opens a pathway for the construction of multiresponsive, structured all-liquid systems by introducing host-guest chemistry, showing promising potential applications in encapsulation, delivery systems, and unique microfluidic devices.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗