Temperature-dependent Behavior Research Articles

Memristive behaviour of Al/rGO-CdS/FTO device at different temperatures: A MATLAB-integrated study

In the present work, a comprehensive study is carried out to investigate the memristive behaviour of reduced graphene oxide (rGO) conjugated cadmium sulphide quantum dot (CdS QD) nanocomposites (rGO-CdS), offering insights into their dynamic response under varying thermal conditions. The study integrates experimental analysis with MATLAB simulation to provide a detailed understanding of the complex interplay between different operating temperature (300K, 350K, 400K, and 450K) and memristive behavior in rGO-CdS nanocomposites. Different structural and chemical characterizations were carried out which confirms the formation of rGO-CdS nanocomposites. A sandwich structured device was fabricated with the synthesized rGO-CdS nanocomposites using Aluminum (Al) as top and Fluorine doped tin oxide (FTO) as bottom electrode. The influence of operating temperature on hysteresis behaviour of the fabricated Al/rGO-CdS/FTO device was investigated using Keithley 2450 source meter by sweeping a direct current (dc) voltage (−5 V → 5 V → −5 V). Notably, we observe a positive temperature coefficient in the device current, with maximum and minimum recorded current of |1.29mA| and |0.66mA| at 450K and 300K respectively. The current-voltage (I-V) behavior observed in the device reveals that in the low resistance state (LRS), conduction is dominated by bulk-limited mechanisms. However, in the high resistance state (HRS), conduction involves contributions from both Schottky barriers and the Pool-Frenkel effect. A MATLAB based linear drift model was used to simulate the device responses at different temperatures using the experimental data. The study provides first comprehensive analysis of temperature dependent hysteresis behaviour of Al/rGO-CdS/FTO device, integrating MATLAB simulation to glean valuable insights into its operation and possible applications as memristive material across different temperature regimes.

Fluorescent, pH, and UCST Responsive Polymer Nanomaterials for Treatment of Recurrent Miscarriage.

Recurrent miscarriage (RM), defined as three or more consecutive spontaneous miscarriages, affects many women of childbearing age. The pathological basis of RM is an imbalance in apoptosis, with the MDM2-p53 pathway playing a crucial role. In this study, we synthesized poly(6-acetoxyl-ε-caprolactone)-graft-(4-amino-benzimidazole) (PCCL-4-ABI) by modifying poly(6-acetoxyl-ε-caprolactone) (PCCL) with 4-amino-benzimidazole (4-ABI). The introduction of carboxyl and 4-ABI groups endowed the PCL backbone with fluorescence, pH responsiveness, and UCST responsiveness. The temperature-dependent release behavior of compound 1-loaded PCCL-4-ABI nanofluorescent materials was attributed to UCST transition. We successfully developed a novel nanofluorescent polymer drug delivery platform, PCCL-4-ABI@1, and evaluated its regulatory effects on p53 and MDM2 in trophoblast cells (HTR-8/SVneo). The results showed that the system loaded with low molecular weight heparin increased MDM2 and decreased p53 expression in a dose-dependent manner, thereby inhibiting trophoblast cell apoptosis. This study developed a biodegradable poly(ε-caprolactone) with UCST behavior, significant for the advancement of thermoresponsive fluorescent nanoparticle systems.

Coexistence of multiple magnetic interactions in oxygen-deficient V2O5 nanoparticles

This paper reports on the spin glass-like coexistence of competing magnetic orders in oxygen-deficient V2O5 nanoparticles with a broad size distribution. X-ray photoelectron spectroscopy yields the surface chemical stoichiometry of nearly V2O4.65 due to significant defect density. Temperature-dependent electrical conductivity and thermopower measurements demonstrate a polaronic conduction mechanism with a hopping energy of about 0.112 eV. The V2O5-δ sample exhibits strong field as well as temperature-dependent magnetic behaviour when measured with a SQUID magnetometer, showing positive magnetic susceptibility across the temperature range of 2-350 K. Field-cooled and zero-field-cooled data indicate hysteresis, suggesting glassy behaviour. The formation of small polarons due to oxygen vacancy defects, compensated by V4+ charge defects, results in Magneto-Electronic Phase Separation (MEPS) and various magnetic exchanges, as predicted by first-principle calculations. This is evidenced by the strong hybridisation of V orbitals in the vicinity of vacant oxygen site. An increase in V4+ defects shows an antiferromagnetic (AFM) component. The magnetic diversity in undoped V2O4.9 originates from defect density and their random distribution, leading to MEPS. This involves localised spins in polarons and ferromagnetic (FM) clusters on a paramagnetic (PM) background, while V4+ dimers induce AFM interactions. Electron paramagnetic resonance spectra measured at different temperatures indicate a dominant paramagnetic signal at a g-value of 1.97 due to oxygen defects, with a broad FM resonance-like hump. Both signals diminish with increasing temperature. Neutron diffraction data rules out long-range magnetic ordering, reflecting the composition as V2O4.886. Despite the FM hysteresis, no long-range order is observed in neutron diffraction data, consistent with the polaron cluster-like FM with MEPS nature. This detailed study shall advance the understanding of the diverse magnetic behaviour observed in undoped non-magnetic systems.

Multi-metric luminescence properties of Sm3+/Er3+ doped Ca2Ga2GeO7: Excitation, time, and temperature

In this study, we explored the potential of Sm3+/Er3+-doped Ca2Ga2GeO7 (CGGO:RE, RE = Sm/Er) as an innovative phosphor, harnessing its versatile photoluminescence properties that depend on various factors, including the excitation wavelength, time, and temperature. Our CGGO:Sm and CGGO:Er samples exhibited promising green and red emissions under UV/Near-UV (NUV) excitation and chromatic changes depending on the excitation wavelength. These color-changing characteristics hold promise for applications in the fields of NUVLEDs and optoelectronics. Furthermore, we observed a significant change in the emission hues of CGGO:Sm as a function of time. We suggest that this moment-color change can be utilized in optical chronometry. Additionally, outstanding thermometric behavior was observed in the upconversion spectra of CGGO:Er. Interestingly, the temperature-dependent behaviors of the luminescent peaks were inconsistent, increasing, constant, or decreasing, which successfully enabled remarkable thermometric performance. Our findings on the multi-metric luminescence properties of CGGO:RE demonstrated the potential of this material to be applied in various fields and highlight its versatility.

Determination of acoustic properties of paraffin oil mixed with activated coal nanoparticles or SPAN80 using only BAW time delay measurement

An important aspect of controlling the properties of liquids relates to their use in modern engines powered by composite materials. In this context, controlling the properties of industrial fluids containing micro- and nanoscale particles is essential. Understanding the temperature-dependent behavior of fluid density and elasticity is crucial for proper engine operation. Seven physical parameters of pure paraffin oil, paraffin oil with varying concentrations of activated coal nanoparticles or sorbitane monooleate (SPAN 80) were simultaneously determined using only BAW time delay measurement in the single experimental run. This technique relies on propagating LBAW through the test fluid and measuring the time delay and amplitude of these waves at different temperatures. By calculating temperature coefficients for velocity, density, time delay, and expansion using well-established formulas the physical properties of fluids under study were determined. The frequency of the LBAW used in the experiment was 13 MHz. The length of the liquid sample in the propagation direction of LBAW was ∼ 5 mm. The experiments were carried out within a temperature range of −20 °C to +90 °C. The volume of the test sample was around 1 milliliter. The comparison of the physical properties of different suspensions under these conditions allows us to demonstrate the dependence of the measured properties on the type and composition of the medium tested.

Predicting thermochemical sulfate reduction reaction process and H2S generation in carbonate reservoirs using comprehensive kinetics modeling

Thermochemical sulfate reduction (TSR) is a critical process controlling hydrogen sulfide (H2S) generation in carbonate reservoirs, posing significant economic and safety challenges for the oil and gas industry. This study develops a comprehensive model that integrates detailed thermal, burial, and hydrocarbon generation histories with key TSR kinetic parameters, such as reaction rate constants and activation energies, to predict TSR evolution and H2S generation accurately. A notable feature of the model is to separate and quantify the contributions of different hydrocarbon species (CH4, C2-5, C6-14, and C15+) to the overall TSR process, using the Arrhenius equation to simulate the temperature-dependent behavior of TSR for each hydrocarbon group. The model also accounts for the in-reservoir thermal cracking of heavier hydrocarbons into light hydrocarbons, ensuring predictions closely align with geological processes. Modeling results show that TSR reactions accelerate the depletion of oil and wet gas components. A large amount of CH4 is generated due to both kerogen thermal cracking and alteration of heavy hydrocarbon. Our modeling also allows for accurate prediction of TSR reactions as well as the timing and extent of H2S and CO2 generation over the history of a reservoir. Applications in the Puguang and Hetianhe gas fields validate the model's broad applicability and reliability, capturing extensive TSR activities and being consistent with the observed data. These results underscore the models' robustness in detailed predictions of TSR dynamics across diverse geological settings and its potential as a valuable tool for managing sour gas production, aiding in risk assessment and resource management.

Internal oxidation behavior and its effect on the surface crack formation in a Fe-Mn-Al-C high Mn steel

The correlation between internal oxidation and surface crack was investigated in high Mn steel. Time- and temperature-dependent internal oxidation behaviors are examined in the temperature ranges of 1000– 1250 °C, revealing faster and deeper oxidation along grain boundaries than in grain. Oxides at the internal oxidation layer are confirmed to be MnO and MnAl2O4. The grain boundary penetration depths of the internal oxide increase from 13 to 34 μm as the temperature increases. The tensile crack on the surface of the specimen was evaluated after 5 % straining with 10−3/s strain. Temperature-dependent crack formation probability (LAC/LT) increases also from 0.4 to 1.6 % as the temperature increases. The evolution of the internal oxidation layer during the hot compression test was investigated to clarify its role in surface crack formation. The transition of the internal oxide layer to the external oxide layer was observed. Exfoliation of the external oxidation layer was also confirmed by further compression. Driving force calculation on the internal and external oxides reveals that the abundant oxygen supply originating from the cracking of oxide and thickness reduction of the internal oxide layer transforms the internal oxide layer to scale during the compression. High-resolution analysis of the grain boundary crack reveals the cracking of grain boundary MnAl2O4. The comparison between the grain boundary oxides’ penetration depth and the crack formation behavior clarifies the grain boundary internal oxide’s crucial role in the surface crack formation in a high Mn steel. This study provides vital insights into the surface crack formation mechanism in a Fe-Mn-Al-C-based high Mn steel during hot-rolling processes, highlighting the significance of grain boundary internal oxidation in production.

Design and conductivity optimization of La0.3Sr0.7TiO3/La0.8Sr0.2MnO3 bi-layer structures as tubular segmented-in-series solid oxide fuel cell interconnect☆

This study focused on meeting the stringent stability requirements of tubular segmented-in-series solid oxide fuel cells (SOFCs) in reducing and oxidizing atmospheres. To address this challenge, a bi-layer perovskite ceramic interconnect was designed by controlling the oxygen partial pressure, because of the strong correlation between the conductivity of strontium-doped lanthanum titanate (LST) and the oxygen partial pressure. The LST powder was prepared using solid-phase and sol-gel methods, and their influence on particle size and sintering behavior was compared. LST/lanthanum strontium manganite (LSM) bi-layer ceramic interconnects with varying thicknesses were fabricated through screen printing and co-sintering. The results demonstrate favorable interfacial bonding and excellent chemical compatibility between the ceramic layers. The conductivity of the bi-layer interconnect exhibits a temperature-dependent behavior, peaking at 550 °C. Simulation calculations and research findings validate that the conductivity of the bi-layer interconnect is determined by the thickness of the LSM layer and the oxygen partial pressure at the interconnect interface. Optimal conductivity is achieved with a bi-layer interconnect consisting of approximately 15 μm of LST and 4 μm of LSM. This can be attributed to the efficient regulation of oxygen partial pressure at the interface, effectively mitigating LSM decomposition caused by low oxygen partial pressure and the subsequent reduction in conductivity. These results provide valuable fundamental data and methodology for the development of high-performance interconnects for tubular segmented-in-series SOFCs.

Temperature Dependent Thermodynamical and Thermoelectric Behaviour of Hafnium Based Insulators: An Ab-inito Characterization

Temperature Dependent Thermodynamical and Thermoelectric Behaviour of Hafnium Based Insulators: An Ab-inito Characterization

Temperature-dependent hydrogen-induced crack propagation behaviour and mechanism in polycrystalline α-iron: Insights from molecular dynamics simulations

Understanding the interactions between hydrogen and material integrity in polycrystalline α-Fe is essential for advancing the reliability of critical infrastructure and energy systems. In this study, molecular dynamics simulations were implemented to pinpoint the crack propagation behaviour and mechanism in polycrystalline α-Fe under various hydrogen concentrations and temperatures. The results show that a phase transition from body-centred cubic to face-centred cubic structure first occurs at the crack tip, followed by grain boundary-mediated plasticity activities at room temperature devoid of hydrogen. A limited amount of hydrogen atoms (H/Fe atomic ratio<1%) induces twinning emission from the tip, and increasing temperature further enhances dislocation plasticity as a consequence of decreased unstable stacking fault energy, thereby leading to the blunting of the crack tip. At high hydrogen concentrations (H/Fe atomic ratio>1%), the formed hydrides ahead of the crack tip suppress the phase transition, and concurrently temperature-enhanced dislocation plasticity disappears. As a consequence, the crack propagation proceeds via grain boundary cavity nucleation and growth, and ultimately evolves into intergranular fracture. These findings provide an atomistic-level explanation for temperature-dependent hydrogen-crack interaction mechanisms, and reveal a transition in the fracture mode from ductile transgranular to intergranular failure associated with locally high hydrogen concentrations found in the experiments.

Temperature-dependent dielectric behavior of A6B2O17 (A = Zr, Hf; B = Nb, Ta) phases

We report on temperature-dependent dielectric behavior of disordered ternary A6B2O17 (A = Zr, Hf; B = Nb, Ta)-form oxides in the GHz frequency range. The microwave dielectric properties including relative permittivity, dielectric loss, and temperature-dependent relative permittivity were characterized using cylindrical dielectric resonators using a resonant post measurement technique. Dielectric measurements through the resonant post method approach generally agree with dielectric measurements of A6B2O17 bulk ceramics measured through standard resonant post techniques. Coefficients describing the temperature-dependent relative permittivity for ternary A6B2O17 phases are strongly positive, suggesting contributions to polarizability arising from long-range mechanisms potentially associated with structural disorder. These observations support the working hypothesis that material functionality can be engineered by the chemical diversity and structural disorder possible in high configurational entropy A6B2O17 phases.

Anomalous temperature-dependent strength of copper alloy manufactured by laser-beam powder bed fusion

This study reports an anomalous temperature-dependent tensile behavior of laser-beam powder bed fusion (PBF-LB) processed Cu–Cr–Zr alloy. The yield strength of the alloy initially decreases as the temperature increases to 200±5 MPa and then increases to 350±11 MPa at 500°C before reducing to 234±6 MPa at 600°C. The microstructure consists of elongated Cu grains with a high concentration of Cr solute (∼1 mass%), resulting from rapid solidification during the PBF-LB process. Transmission electron microscopy for the specimens deformed at 500°C revealed the presence of numerous nanoscale Cr-rich particles embedded inside the supersaturated solid solution of the Cu matrix. Nanoscale particles can act as barriers to dislocation motion, leading to an increase in internal stress during plastic deformation at elevated temperatures. This work provides the high potential of post heat treatments for achieving superior mechanical performance using high solute supersaturation formed by the PBF-LB process.

Temperature-regulated gas adsorption on LTA zeolites: Observation of sorption isotherms for methane, hydrogen, nitrogen and carbon dioxide

Temperature-regulated gas adsorption of various zeolite LTAs with different cations of Cs2+, K+, Na+, and Ca2+ (namely, Cs-A, 3A, 4A, and 5A) was analysed in the presence of different gas molecules of H2, CO2, N2, and CH4 for pressures up to 800 kPa and temperatures ranging from 77.15 to 363.15 K. Over the range of test conditions, zeolite 5A (containing Ca2+ cations) exhibited the highest uptake at 800 kPa for CO2, H2, CH4, and N2, with capacity values of 5.69 mmol.g−1, 1.14 mmol.g−1, 6.60 mmol.g−1, and 6.10 mmol.g−1, at 298.15 K and 201.15 K respectively. Zeolite 4A (containing Na+ cations) exhibited 0.74 mmol.g−1 for H2 adsorption at 201.15 K, and 800 kPa. In contrast, pores were inaccessible to H2 on ion-exchange Cs-A zeolite at a temperature range of 77.15–343.15 K, due to larger cation Cs2+ (CsA) comparison with Na+ (4A). Interestingly, zeolite 3A (containing K+ cations) showed a negligible capacity for the larger gas molecules, CH4 and N2, ascribed to the pore space blocked by the larger K+ cations (relative to the smaller Na+ and Ca2+ cations). Zeolite 3A exhibited a temperature-dependent behaviour (i.e., presumably a “trapdoor” effect) with H2 wherein adsorption was negligible at 77.15 K, but was significant above approximately 200 K. For N2, zeolite 4A exhibits similar temperature-regulated adsorption characteristics (i.e., presumably a “trapdoor” mechanism as well). These zeolite materials used in various temperature swing processes could be particularly beneficial in natural hydrogen production (with H2/N2 separation with 3A), the production of synthetic fuels from CO2/H2 mixtures (with both 3A and 4A), CO2 capture from waste streams, and applications for H2/N2 separation.

Effects of temperature on the anisotropic mechanical properties and failure mechanisms of Sheet Molding Compounds

Sheet Molding Compounds (SMC) are widely used in many industries. Due to their high in-mold flow, fibers tend to align during the component processing and generate anisotropic mechanical properties. Besides, being SMCs thermoset composites, their application in high temperature environments often results to be of interest. In this research, the fiber orientation and temperature-dependent mechanical behavior and failure mechanisms were studied. First, materials were compression molded into plates, promoting fiber orientation. Then, the materials’ orientation-dependent viscoelastic behavior was analyzed by Dynamic Mechanical Analysis, and their anisotropy level was assessed at quasi-static tensile, bending and compression modes at 23 °C and 130 °C. Finally, the failure mechanisms were inspected by confocal microscopy to evaluate the influence of temperature and fiber orientation on them. The results demonstrate how the temperature influences the material’s mechanical performance and their anisotropic behavior, especially at 45°. Likewise, temperature alters failure mechanisms, by triggering the fiber-matrix interface failure.

Estimating equivalent elastic properties of frozen clay soils using an XFEM-based computational homogenization

This study addresses the challenge of estimating the elastic properties of heterogeneous frozen clay soils by introducing a comprehensive approach that combines analytical and numerical models. The frozen clay soil is treated as a mixture composed of frozen clay-water composites and nonclay mineral inclusions. An inversion algorithm is employed to deduce the elastic properties of the matrix (clay-water composites) of two artificially frozen sandy clay samples with known temperature-dependent elastic properties. Subsequently, a two-dimensional numerical simulation using the eXtended Finite Element Method (XFEM) is conducted to carry out numerical homogenization by considering the imperfect bond among frozen clay-water composites and nonclay minerals. The numerical homogenization model offers insights into the temperature-dependent behavior of the interface stiffness parameter. The numerical homogenization results are compared with conventional numerical homogenization approaches like the FEM, which rigidly defines the bonding between inclusions and the matrix. The comparison indicates that the neglect of imperfect bonds among clay-water composites and nonclay minerals will lead to unrealistic outcomes in cases with a high fraction of inclusions. This integrated approach advances the understanding and prediction of elastic properties of frozen clay soils by considering their heterogeneous nature.

Solid-State Lithium-Ion Superionic Electrolytes with Reduced Moisture Sensitivity

The remarkable safety and high energy density of solid-state batteries (SSBs) created significant advantages in the development of next-generation energy storage. The properties of these batteries are highly dependent on the characteristics of solid-state electrolytes (SSEs), making them a crucial material in the development of such batteries. Following diverse principles of material design, lithium halide SSEs, particularly Li3InCl6, open new opportunities in the development of SSBs due to their unique properties including broad electrochemical stability window, high lithium-ion conductivity, and excellent deformability. Through a mechano-thermal synthesis approach, Li3InCl6 demonstrates substantial ionic conductivity at room temperature. We studied the temperature-dependent behavior of Li3InCl6 by using in-situ/operando techniques such as XRD and XPS. However, its susceptibility to moisture poses a significant challenge for practical implementation in SSBs. To overcome this limitation, this research is focused on a novel solution: hafnium doping of Li3InCl6. Integrating hafnium into the Li3InCl6 structure results in a substantial improvement in electrochemical performance. The Li2.6In0.6Hf0.4Cl6 solid-state electrolyte not only showcases heightened ionic conductivity but also demonstrates improved resistance to moisture. The achieved ionic conductivity reaches approximately 1 mS cm-1, marking a significant 3.5-fold increase compared to Li3InCl6. Noteworthy is the fact that, after 5 hours of exposure to air with 15% humidity, the observed reduction in ionic conductivity for Li2.6In0.6Hf0.4Cl6 is 37%, a notably lower decrease compared to the 57% reduction seen in Li3InCl6.The efficacy of hafnium doping provides a crucial advancement in the field of solid-state electrolytes, promising a transformative impact on next-generation energy storage systems.

Investigating Temperature-Dependent Dynamics of SEI Growth and Battery Degradation

Several studies have contributed to the current understanding of the temperature-dependent behavior of solid-electrolyte interphase (SEI) formation in lithium-ion batteries and its impact on battery capacity and lifespan. Liu et al. developed a thermal-electrochemical model that revealed the complex interplay between diffusivity, reaction kinetics, and temperature on SEI growth1. Leng et al. presented an electrochemistry-based electrical model to examine the temperature's effect on battery aging2. Alipour et al. reviewed temperature-dependent electrochemical properties3, while Lubhani Mishra et al. provided a detailed physics-based analysis of battery degradation and temperature inhomogeneities4. These studies collectively indicate higher temperatures accelerating and promoting growth of compact and less permeable SEI structures leading to an increase in capacity loss and cell resistance, and lower temperatures resulting in slow ionic transport through the SEI also causing higher ohmic loss. In the present work, we study SEI growth and resulting effect on battery capacity fade using continuum scale modeling under the assumption of constant battery cell temperature as well as considering actual dynamically changing temperature data from experiments. SEI growth under these two considerations is compared and the comparison is used in determining scenarios where considering dynamically varying temperature is crucial for accuracy. The detailed analysis of the internal states from the simulation results contributes to the understanding of the effect of the thermal dynamics on battery cell degradation due to SEI growth. To achieve these objectives, a physics-based model, specifically the Single Particle Model (SPM), is utilized. The model uses temporal temperature data obtained from past experimental studies as well as temperature dependent properties of SEI provided in the literature as inputs for this investigation. The ultimate aim of this study is to better understand how temperature influences SEI characteristics, thereby contributing to improved battery performance and longevity across diverse thermal environments. References Liu, L., Park, J., Lin, X., Sastry, A. M., & Lu, W. (2014). A thermal-electrochemical model that gives spatial-dependent growth of solid electrolyte interphase in a Li-ion battery. Journal of power sources, 268, 482-490.Leng, F., Tan, C. M., & Pecht, M. (2015). Effect of temperature on the aging rate of Li-ion battery operating above room temperature. Scientific reports, 5(1), 12967.Alipour, M., Ziebert, C., Conte, F. V., & Kizilel, R. (2020). A review on temperature-dependent electrochemical properties, aging, and performance of lithium-ion cells. Batteries, 6(3), 35.Mishra, L., Subramaniam, A., Jang, T., Garrick, T. R., & Subramanian, V. R. (2022, October). Model Development for Temperature-Dependent Degradation in Large Format Lithium-Ion Batteries. In Electrochemical Society Meeting s 242 (No. 28, pp. 1075-1075). The Electrochemical Society, Inc.

Diffusion and structure of propylene carbonate-metal salt electrolyte solutions for post-lithium-ion batteries: From experiment to simulation.

The diffusion of cations in organic solvent solutions is important for the performance of metal-ion batteries. In this article, pulsed field gradient nuclear magnetic resonance experiments and fully atomistic molecular dynamic simulations were employed to study the temperature-dependent diffusive behavior of various liquid electrolytes representing 1M propylene carbonate solutions of metal salts with bis(trifluoromethylsulfonyl)imide (TFSI-) or hexafluorophosphate (PF6-) anions commonly used in lithium-ion batteries and beyond. The experimental studies revealed the temperature dependence of the diffusion coefficients for the propylene carbonate (PC) solvent and for the anions following an Arrhenius type of behavior. It was observed that the PC molecules are the faster species. For the monovalent cations (Li+, Na+, K+), the PC solvent diffusion was enhanced as the cation size increased, while for the divalent cations (Mg2+, Ca2+, Sr2+, Ba2+), the opposite trend was observed, i.e., the diffusion coefficients decreased as the cation size increased. The anion diffusion in LiTFSI and NaTFSI solutions was found to be similar, while in electrolytes with divalent cations, a decrease in anion diffusion with increasing cation size was observed. It was shown that non-polarizable charge-scaled force fields could correspond perfectly to the experimental values of the anion and PC solvent diffusion coefficients in salt solutions of both monovalent (Li+, Na+, K+) and divalent (Mg2+, Ca2+, Sr2+, Ba2+) cations at a range of operational temperatures. Finally, after calculating the radial distribution functions between cations, anions, and solvent molecules, the increase in the PC diffusion coefficient established with the increase in cation size for monovalent cations was clearly explained by the large hydration shell of small Li+ cations, due to their strong interaction with the PC solvent. In solutions with larger monovalent cations, such as Na+, and with a smaller solvation shell of PC, the PC diffusion is faster due to more liberated solvent molecules. In the salt solutions with divalent cations, both the anion and the PC diffusion coefficients decreased as the cation size increased due to an enhanced cation-anion coordination, which was accompanied by an increase in the amount of PC in the cation solvation shell due to the presence of anions.

Thermoresponsive On-Demand Adhesion and Detachment of a Polyurethane-Urea Bioadhesive.

The development of bioadhesives with strong adhesion and on-demand adhesion-detachment behavior is still critically important and challenging for facilitating painless and damage-free removal in clinical applications. In this work, for the first time, we report the easy fabrication of novel polyurethane-urea (PUU)-based bioadhesives with thermoresponsive on-demand adhesion and detachment behavior. The PUU copolymer was synthesized by a simple copolymerization of low-molecular-weight, hydrophilic, and biocompatible poly(ethylene glycol), glyceryl monolaurate (GML, a special chain extender with a long side hydrophobic alkyl group), and isophorone diisocyanate (IPDI). Here, GML was expected to not only adjust the temperature-dependent adhesion behavior but also act as an internal plasticizer. By simple adjustment of the water content, the adhesion strength of the 15 wt % water-containing PUU film toward porcine skin is as high as 55 kPa with an adhesion energy of 128 J/m2 at 37 °C. The adhesion strength dramatically decreases to only 3 kPa at 10 °C, exhibiting switching efficiency as high as 0.95. Furthermore, the present PUU-based adhesive also shows good on-demand underwater adhesion and detachment with a cell viability close to 100%. We propose that biomaterial research fields, especially novel PUU/polyurethane (PU)-based functional materials and bioadhesives, could benefit from such a novel thermoresponsive copolymer with outstanding mechanical and functional performances and an easy synthesis and scaled-up process as described in this article.

Temperature-Induced Nanoarchitectonics of Monolayer Self-Assembly of Heterocoronene-Based Discotic Liquid Crystals.

Enhancing molecular self-assembly at the monolayer level offers significant potential for various applications. For monolayers made of π-conjugated discotic liquid crystal (DLC) molecule nanowires, achieving precise separation and alignment of these nanowires has been a long-standing challenge. This research explores an approach using the manipulation of subphase temperature and surface pressure within a Langmuir trough to control molecular nanowire separation. We observe notable temperature-dependent behavior: as the temperature increases from 5 to 30 °C, the monolayer collapse pressure rises steadily. In contrast, temperatures from 35 to 50 °C exhibit an initial small plateau with a nonzero slope that becomes more distinct with rising temperature. Our study of Langmuir-Blodgett (LB) films provides crucial insights into the monolayer's structure. At lower temperatures, the LB films show coalesced molecular nanowires, whereas at higher temperatures, the DLC nanowires separate and form an interconnected network. Remarkably, upon compression, this network transforms into a compact, highly uniform monolayer. To explain these temperature-dependent behaviors, we examine the area relaxation curves, which indicate a two-step molecular loss mechanism involving desorption and monolayer collapse due to the nucleation and growth of critical nuclei. This extensive study offers valuable insights into the dynamic interaction of the temperature, surface pressure, and molecular assembly, enhancing our understanding of the fundamental processes in monolayer self-assembly.