FTIR investigation of the interfacial properties and mechanisms of CO2 sorption in porous ionic liquids
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
SEARCH · Engineering Papers
Results for “ionic interactions”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Double Doping of Semiconducting Polymers Using Ion-Exchange with a Dianion
The interactions between counterions and electronic carriers in electrically doped semiconducting polymers are important for delocalization of charge carriers, electronic conductivity, and thermal stability. The introduction of a dianions in semiconducting polymers leads to double doping where there is one counterion for two charge carriers. Double doping minimizes structural distortions, but changes the electrostatic interactions between the carriers and counterions. Polymeric ionic liquids (PIL) with croconate dianions are helpful to investigate the role of the counterion in p-type semiconducting polymers. PILs prevent diffusion of the cation into the semiconducting polymers during ion exchange. The redox-active croconate dianions undergo ion exchange with doped semiconducting polymers depending on their ionization energy. Croconate dianions are found to reduce doped films of poly(3-hexyl thiophene), but undergo ion exchange with a polythiophene with tetraethylene glycol side chains, P(g 4 2T-T), that has a lower ionization energy. The croconate dianion maintains crystalline order in P(g 4 2T-T) and leads to a lower activation energy for the electrical conductivity than PF 6 – counterions. The control of the doping level with croconate allows optimization of the thermoelectric performance of the semiconducting polymer. Finally, the thermal stability of the doped films of P(g 4 2T-T) is found to depend strongly on the nature of the counterion.
36 MATERIALS SCIENCE↗
Ionic Liquid Facilitated Solvent‐Phase Polymerization of Ultrasmooth Coatings of Polycatecholamines
Mussel-inspired polycatecholamine coatings and films have proven to be versatile materials for surface modification. However, the progress of chemically modified coatings with tailored properties has been slow due to the lack of definitive evidence of their polymeric structure. Polycatecholamines form aggregates during polymerization, and their formation mechanism has been a subject of debate owing to their insolubility in traditional molecular solvents. Exploiting the capability of ionic liquids (ILs) to exhibit strong electrostatic interactions, herein, the first solution-phase polymerization approach is reported to achieve polymerization of four catecholamines – dopamine (DA), norepinephrine (NE), L-3,4-dihydroxyphenylalanine (L-DOPA), and adrenaline (AD). Kinetic control over the polymerization process in the solution phase enabled it to follow the process with 1 H NMR spectroscopy, revealing the formation of structural features of resulting complex heterogeneous and soluble polymers. The polymers are both covalent and associative in nature. Solution phase polymerization prevented the formation of large aggregates in the solution, thus facilitating the formation of coatings that are ultra-smooth and have root mean square roughness of the order of sub-nm to nm scale.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
A constitutive model for elastomers tailored by ionic bonds and entanglements
Over the past decade or two, the concept has emerged of using multiple types of weak interactions simultaneously to enhance the mechanical properties of elastomers. These weak interactions include physical entanglements, hydrogen bonds, metal-coordination bonds, dynamic covalent bonds, and ionic bonds. The combination of entanglements and ionic bonding has been minimally explored and is particularly exciting because of the broad application space for polyelectrolytes. In this work, a constitutive model framework is developed to describe the response of elastomers with both ionic bonds and entanglements. Here we formulate a micromechanical model that couples together chain stretching, ionic bond slipping, and entanglement evolution. The ionic bonds provide toughness by enabling plastic deformation in comparison to covalently crosslinked material and add strength compared to a linear polymer. Evolution of the entanglement density is taken as a key mechanism that can govern stiffness, toughness, and self-recovery in elastomers. The model is used to match bulk polyelectrolytes with different fractions of ionic components under a variety of loading histories. The variations in material parameters are then used to help understand the relative importance of different governing mechanisms in the bulk polymers. We show that the theoretical framework can explain our experimental uniaxial tensile experimental results for polyelectrolytes. This model can help to design better material with high stiffness and toughness. We expect that our model can be extended to explain the mechanical behavior of other polyelectrolytes and other soft materials with a wide range of dynamic bonds.
42 ENGINEERING↗
Condensed Phase Water Molecular Multipole Moments from Deep Neural Network Models Trained on Ab Initio Simulation Data
Ionic solvation phenomena in liquids involve intense interactions in the inner solvation shell. For interactions beyond the first shell, the ion–solvent interaction energies result from the sum of many smaller-magnitude contributions that can still include polarization effects. Deep neural network (DNN) methods have recently found wide application in developing efficient molecular models that maintain near-quantum accuracy. In this work, we extend the DeePMD-kit code to produce accurate molecular multipole moments in the bulk and near interfaces. The new method is validated by comparing the DNN moments with those generated by ab initio simulations. The moments are used to compute the electrostatic potential at the center of a molecular-sized hydrophobic cavity in water. The results show that the fields produced by the DNN models are in quantitative agreement with the AIMD-derived values. These efficient methods will open the door to more accurate solvation models for large solutes such as proteins.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Synthesis of imidazolium-mediated Poly(benzoxazole) Ionene and composites with ionic liquids as advanced gas separation membranes
We report thermally rearranged (TR) polymers and ionic polymers are two material classes which have been employed in leading gas separation membranes. This work introduces a novel approach of combining the benzoxazole functionality associated with TR polymers with tailorable cationic groups, yielding a new type of imidazolium-mediated poly(benzoxazole) ionene polymer, “Im-PBO-Ionene” with the aim of enhanced CO 2 separation performance. The structural changes exhibited from the Coulombic interactions between the ionene backbone and the “free” ionic liquid (IL) resulted in enhanced gas separation performance, shown in fundamental characterizations, observed through increased diffusivities and more notably, retained high selectivities and 3x or 5x respective increases in CO 2 permeability upon the addition of 1 or 2 equivalents of IL per polymer repeat unit. These new high-performance ionenes demonstrate the versatility of ionene design and potential of the ionene + IL material platform for gas separation membranes with versatile incorporation of sophisticated functional and structural features.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Persistent opto-ferroelectric responses in molecular ferroelectrics
Persistent photoresponses require optical excitations to metastable states, which are rare of ionic origin due to the indirect photon-ion interaction. In this work, we explore the photoinduced metastable proton states in the proton-transfer type molecular ferroelectric croconic acid.We observe that, after the photoexcitation, the changes of structural and ferroelectric properties relax in ~10 3 s, indicating persistent photoresponses of ionic origin. In contrast, the photoconductivity relaxes within 1 s. The 10 3 s timescale suggests that the ionic metastable states result from proton transfer both along and out of the hydrogen bonds. Furthermore, this discovery unveils an ionic mechanism for the phototunability, which offers persistent opto-ferroelectric control for proton-transfer type molecular ferroelectrics.
36 MATERIALS SCIENCE↗
Ionic-like Superlattices by Charged Nanoparticles: A Step Toward Photonics Applications
Controlling interactions among nanoparticles is paramount to achieving assemblies vital to technologies seeking to exploit their cutting-edge collective properties. Although various techniques have been advanced, robust ones are necessary for upscaling nanoparticle assembly and crystallization. Here, we show that by grafting gold nanoparticles (AuNPs) with charge-end-group-thiolated poly(ethylene glycol), we control the charge of each AuNP. Such control facilitates the formation of various two-dimensional structures of oppositely charged binary constituents at vapor/liquid interfaces. Using surface-sensitive synchrotron X-ray diffraction techniques, we established the formation of distinct checkerboard square lattice structures at a range of pH values and molar ratios of the constituents. By regulating pH, the superlattices can transform from a square to a hexagonal lattice, or vice versa, and to a single-component superstructure at the interface. In conclusion, our recipe for the control of charges and their consequent interactions among nanoparticles can be readily exploited in the assembly of photonics and plasmonics devices in two and three dimensions.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Ionic liquids for carbon capture
This article covers cutting-edge research in ionic liquid-based materials and their impact on carbon capture. Ionic liquids boast high thermal stability, low vapor pressure, and great tunability. They can be deployed as either sorbents or supported liquid membranes for carbon capture and other gas separations. Absorption of CO 2 in ionic liquids can be achieved via physisorption or chemisorption, depending on the strength of the interaction. For physisorption, both CO 2 -anion and cation–anion interactions are important factors in dictating CO 2 solubility. For chemisorption, the reactivity with CO 2 can be tuned by the basicity of the anion while the stability of the ionic liquid can be enhanced by controlling the cation. Marrying ionicity of ionic liquids with porosity leads to novel porous ionic liquids that feature unique properties for facilitating gas transport, while interfacing ionic liquids with microporous membranes allow the ions to gate the pores for selective gas transport. Further, composite materials of ionic liquids with crystalline materials such as metal–organic frameworks offer scalable heterogeneous interfaces to promote selectivity. Future opportunities include controlling the interaction with CO 2 and its transport at the charged or electrified interface with the ionic-liquid electric double layer, as well as combining CO 2 capture and conversion with ionic liquids.
36 MATERIALS SCIENCE↗
Computational Optimization of Room Temperature Usable Capacity for Hydrogen Storage in MFU-4-Type Metal–Organic Frameworks via Pairwise Metal Substitutions
The efficient storage of hydrogen is a critical challenge in the quest for sustainable energy solutions. Current adsorbent-based methods achieve satisfactory storage densities predominantly under cryogenic temperatures and/or high pressures, which imposes problems with cost-efficient and safe implementation of this technology. Materials that can bind hydrogen gas reversibly at ambient temperatures and more moderate pressures could play a pivotal role in enabling hydrogen-powered technologies. In this study, we use reliable computational modeling to investigate two synthetically feasible paths for tuning the enthalpy of H2 binding in MFU-4-type metal–organic frameworks (MOFs), aiming to maximize usable capacity. This study examines MIM4 IICl3(bta)6 (bta– = benzotriazolate) Kuratowski-type clusters as a model for strong binding sites in MFU-4l frameworks. We systematically evaluate the impact of separately tuning the central MII metal ion (which plays a structural role) and the peripheral MI metal ion (which binds the substrate) on the energetics of H2 binding. Our computational study reveals that H2 binding at an MI site mostly follows the trend AgI < CuI < NiI < CoI < AuI while a larger central MII site generally weakens the H2 binding at a MI site. Importantly, we have identified three new combinations of MI and MII to achieve high fractional usable capacities of the total H2 adsorbed under a pressure swing from 5 to 100 bar at room temperature. Additionally, we examine the nature of the binding interaction between the peripheral metal atom and the hydrogen molecule. While charge transfer predominantly induces this interaction, for several atom combinations, a change in the polarization (associated with variations in the ionic radius of the MI binding atom) is another important factor for adjusting the strength of the interaction. We suggest that the proposed compositions of Kuratowski-type clusters are highly desirable synthetic targets for future laboratory study.
Tkachenko, Nikolay V↗
Magnetic field effects on the quantum spin liquid behaviors of NaYbS 2
Spin-orbit coupling is an important ingredient to regulate the many-body physics, especially for many spin liquid candidate materials such as rare-earth magnets and Kitaev materials. The rare-earth chalcogenides NaYbCh 2 (Ch = O, S, Se) is a congenital frustrating system to exhibit the intrinsic landmark of spin liquid by eliminating both the site disorders between Na + and Yb 3+ ions with the big ionic size difference and the Dzyaloshinskii-Moriya interaction with the perfect triangular lattice of the Yb 3+ ions. The temperature versus magnetic-field phase diagram is established by the magnetization, specific heat, and neutron-scattering measurements. Notably, the neutron diffraction spectra and the magnetization curve might provide microscopic evidence for a series of spin configuration for in-plane fields, which include the disordered spin liquid state, 120° antiferromagnet, and one-half magnetization state. Furthermore, the ground state is suggested to be a gapless spin liquid from inelastic neutron scattering, and the magnetic field adjusts the spin orbit coupling. Therefore, the strong spin-orbit coupling in the frustrated quantum magnet substantially enriches low-energy spin physics. This rare-earth family could offer a good platform for exploring the quantum spin liquid ground state and quantum magnetic transitions.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Computational Investigation of the Bonding in [(η 5 –Cp′) 3 (η 1 –Cp′)M] 1– (M = Pu, U, Ce)
Despite the similar ionic radii for Ce 3+ , U 3+ , and Pu 3+ , [(η 5 –Cp′) 3 (η 1 –Cp′)Ce] 1– (Cp′ = C 5 H 4 SiMe 3 , 1-Ce) displays a significantly longer η 1 –Cp′ distance in the solid state compared to the U 3+ and Pu 3+ analogues. To better understand this observation, a theoretical investigation was undertaken to examine the differences in bonding between the actinides 1-Pu and 1-U and how they compare with 1-Ce. The results show that although the bonding is largely ionic and dominated by ligand (2p)–metal (6d/5d) interactions, the polarization of 5f orbitals plays a significant role for 1-Pu and 1-U compared to the 4f-orbitals of 1-Ce. The lack of Ce(4f) interactions is compensated for by increased participation of the Ce(5d) orbitals relative to the actinide 6d orbitals, particularly for the σ-bound η 1 –Cp′ ligand. Furthermore, the use of multiple theoretical approaches including topological, localization, and energy decomposition approaches shows that 1-Pu and 1-U are very similar in covalent character compared to 1-Ce, though the composition and energy of the different interactions suggest that 1-U presents the strongest overall interactions.
Actinides↗
Dicopper( i ) complexes of a binucleating, dianionic, naphthyridine bis(amide) ligand
The dinucleating ligand, 1,8-naphthyridine-2,7-bis(2,6-diisopropylphenyl)carboxamide (NBDA), was synthesized by palladium-catalyzed aminocarbonylation. This ligand was treated with two equivalents of mesitylcopper(I) in the presence of [nBu4N]X (X = Cl, N3) to give the anionic complexes [nBu4N][Cu2(NBDA)(μ-Cl)] and [nBu4N][Cu2(NBDA)(μ-N3)]. Treatment of H2NBDA with mesitylcopper(I) and two equivalents of xylyl isocyanide led to the formation of a charge-neutral dicopper(I) complex, [Cu2(NBDA)(CNXyl)2], displaying two isocyanide ligands, each terminally bound to one of the copper atoms. The complexes were characterized by NMR and IR spectroscopy, as well as by single-crystal X-ray diffraction analysis. Electrochemical characterization of the complexes using cyclic voltammetry revealed a reversible ligand-based reduction between -1.65 and -2.0 V vs. Fc/Fc+. DFT calculations suggest a more ionic bonding character and weaker Cu-Cu interactions in the NBDA complexes compared to those with other 1,8-naphthyridine-based ligands. This is congruent with intermetallic separations of over 3 Å induced by relatively strong coordination of the copper atoms to the amide nitrogen donor atoms observed in the solid state molecular structures.
Sévery, Laurent↗
Molecular structures of residual solvent in polyacrylonitrile based electrolytes: Implications for conductivity and stability
Lithium-ion batteries increasingly play significant roles in modern technologies; however, increased energy density also raises concerns about electrolyte safety. Traditional electrolytes that use volatile organic solvents face risks of thermal runaways and fires from electrode shorting. In response, polymer-based solid electrolytes have been developed for replacement. Polyacrylonitrile (PAN) is a promising fire-resistant component for electrolyte fabrication, but its limited solubility necessitates using low-volatility solvents, which are notoriously difficult to remove in subsequent drying processes. Here, we use femtosecond two-dimensional infrared spectroscopy to provide an in-depth understanding of how residual solvent from processing affects the molecular structures and dynamics within a polymer electrolyte. To this end, linear and nonlinear infrared spectroscopies are employed to interrogate the molecular interactions in PAN-based electrolytes containing various contents of N,N-dimethylformamide (DMF). We show that the amount of DMF within the PAN electrolyte affects the Li+ structure. Further, the coordination can proceed through the carbonyl group and/or the amide nitrogen to form antiparallel structures with the nitrile groups of PAN through dipole–dipole interactions. The free motion of DMF is drastically inhibited upon interaction with Li+ and PAN, which decreases the ionic conductivity and potentially affects the stability (resistance toward removal and chemical decomposition). These findings have implications for the design and processing of solid polymer electrolytes.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Reward based optimization of resonance-enhanced piezoresponse spectroscopy
Dynamic spectroscopies in scanning probe microscopy (SPM) are critical for probing material properties, such as force interactions, mechanical properties, polarization switching, electrochemical reactions, and ionic dynamics. However, the practical implementation of these measurements is constrained by the need to balance imaging time and data quality. Signal to noise requirements favor long acquisition times and high frequencies to improve signal fidelity. However, these are limited on the low end by contact resonant frequency and photodiode sensitivity and on the high end by the time needed to acquire high-resolution spectra or the propensity for sample degradation under high field excitation over long times. The interdependence of key parameters such as instrument settings, acquisition times, and sampling rates makes manual tuning labor-intensive and highly dependent on user expertise, often yielding operator-dependent results. These limitations are prominent in techniques like dual amplitude resonance tracking in piezoresponse force microscopy that utilize multiple concurrent feedback loops for topography and resonance frequency tracking. Here, a reward-driven workflow is proposed that automates the tuning process, adapting experimental conditions in real time to optimize data quality. Furthermore, this approach significantly reduces the complexity and time required for manual adjustments and can be extended to other SPM spectroscopic methods, enhancing overall efficiency and reproducibility.
47 OTHER INSTRUMENTATION↗
Sandia Laboratories in-house activities in support of solar thermal large power applications
The development of thermal energy storage subsystems for solar thermal large power applications is described. The emphasis is on characterizing the behavior of molten nitrate salts with regard to thermal decomposition, environmental interactions, and corrosion. Electrochemical techniques to determine the ionic species in the melt and for use in real time studies of corrosion are also briefly discussed.
Mar, R. W.↗
Computer-aided design of polymers and composites
This book on computer-aided design of polymers and composites introduces and discusses the subject from the viewpoint of atomic and molecular models. Thus, the origins of stiffness, strength, extensibility, and fracture toughness in composite materials can be analyzed directly in terms of chemical composition and molecular structure. Aspects of polymer composite reliability are considered along with characterization techniques for composite reliability, relations between atomic and molecular properties, computer aided design and manufacture, polymer CAD/CAM models, and composite CAD/CAM models. Attention is given to multiphase structural adhesives, fibrous composite reliability, metal joint reliability, polymer physical states and transitions, chemical quality assurance, processability testing, cure monitoring and management, nondestructive evaluation (NDE), surface NDE, elementary properties, ionic-covalent bonding, molecular analysis, acid-base interactions, the manufacturing science, and peel mechanics.
Kaelble, D. H.↗
Probing specific ion effects at air-aqueous dibutyl phosphate interfaces using vibrational sum frequency generation spectroscopy
Molecular properties at air–liquid and liquid–liquid interface hold the key to many processes involving molecular transport across phase boundaries from aerosol formation to carbon cycling and material separation using solvent extraction techniques. Using dibutyl phosphate (DBP) as a representative for partially aqueous soluble surfactants, the specific ion effect (SIE) of the Hofmeister series cations Cs + , Na + , Li + , and Mg 2+ on the partition and interaction between surfactant molecules and water molecules in the air–aqueous interface are investigated using vibrational sum frequency generation spectroscopy and surface tension measurements. In the presence of 1 mM and 1M bulk aqueous phase ionic strength salt concentrations, fundamental qualitative relationships are observed for the salting out of DBP relative to bulk aqueous phase nitrate salt concentrations and the specific cations species. At 1 mM ionic strength, the interfacial charge and hence the interfacial potential modulates the electrostatic interactions; in particular, the counter cations partially screen the negatively charged interface induced by the DBP in a direct Hofmeister order. At 1M ionic strength, the electric field at the interface or interfacial potential is effectively neutralized, and the counter cations promote the partitioning of DBP to the interface depending on their specific interaction with the DBP head group and metal ion hydration properties. The present results lay a foundation to study SIEs of heavier metals on hydrophobic-aqueous DBP interfaces.
Louie, Christina [Washington State University, Pul↗