Interfacial Interaction Energy Research Articles

Molecular Mechanism of Physical and Mechanical Improvement in Graphene/Graphene Oxide-Epoxy Composite Materials.

The performance provided by graphene (Gr) and graphene oxide (GO) additives can be improved by achieving strong adhesion and uniform dispersion in the epoxy resin matrix. In this study, molecular modeling and simulation of DGEBA/DETA based epoxy nanocomposites containing Gr and GO additives were performed. Density functional theory and molecular dynamics simulations were used to investigate interfacial interaction energies and Young's Modulus. Improvement in the interaction energies was studied by controlling the epoxy:hardener ratio, type and the number of oxygen-containing functional groups on the GO, the mass percentage of Gr/GO filler in the epoxy matrix, size and dispersion of GO in the cell. It was demonstrated that functional groups with up to 10 % oxygen content in GO significantly increase interfacial interaction energy for large size Gr/GO. Increasing DETA type amine ratio in the preparation of epoxy polymers increases the interaction energy for high oxygen content while decreasing the interaction energy for low oxygen content in GO for small size GO with edge functional groups. The performance of material dramatically decreased even at high DETA hardener and high GO mass percentages when the aggregation factor of Gr/GO was included in simulations that explain lower Gr/GO percentages in the experimental studies.

Designing High-Performance Green Tire Treads by Reinforcing the Styrene-Butadiene Rubber/Silica Interface with Chain Difunctionalization

For green tires, monofunctionalization of rubber has been extensively studied to enhance the interface between rubber and silica. However, the effect of chain difunctionalization has not been reported. In this work, the difunctionalized styrene-butadiene rubber (SBR-DF) was first prepared by grafting small molecules with different functional groups (3-mercaptopropionic acid, 3-mercaptoethanol, and mercaptosilane) to end-group functionalized SBR through thiol-ene click reaction. Then, the molecular dynamics simulation was adopted to calculate the interaction energy between SBR-DF and silica. The results showed that the chain difunctionalization can significantly increase the interfacial interaction energy between them, which was further validated by using RPA and SEM. Moreover, the introduced siloxane groups in the rubber chain can greatly improve the interfacial interaction energy by more than 20%, which can achieve the uniform dispersion of silica. As a result, the SBR-DF/Silica composites showed the excellent dynamic mechanical properties, such as high wet slip resistance (21% increase), low rolling resistance (23% reduction) and high wear resistance (20% reduction). As a result, the energy consumption of SBR-DF/Silica composites was reduced, which endowed green tires with excellent safety. In summary, this work provides a new and effective strategy for manufacturing the energy-saving, green and safe design of “green tires”.

Optical and mechanical properties of waterborne nano-CaCO3/polyethylene coatings: experimental, DFT, and wave optics investigation

This study analyzed the impact of nano-CaCO3 content on the optical and mechanical properties of waterborne nano-CaCO3/polyethylene coatings. The results showed a marginal reduction in lightness (L*) and contrast ratio alongside incremental nano-CaCO3 content, but substantial increases in scrubbing resistance and stain resistance were observed. Nano-CaCO3 enhances shear resistance through intermolecular interactions. It revealed the interface interaction energy of the nano-CaCO3/polyethylene model at 11.90 kJ/mol. Measured and calculated optical properties confirmed a decrease in L* and contrast ratio when TiO2 was replaced by nano-CaCO3. Optical properties were predicted using DFT, and response and impedance matching with varying nano-CaCO3 content were assessed using the wave optics model.

Membrane fouling characteristics and mechanisms in coagulation-ultrafiltration process for treating microplastic-containing water

Microplastics (MPs) are recognized as a significant challenge to water treatment processes due to their ability to adsorb or accumulate alginate foulants, impacting the coagulation-ultrafiltration (CUF) process. In this study, the mechanisms of membrane fouling caused by MPs under varying dosages of polymeric aluminum chloride (PAC) coagulant in the CUF process were investigated. It was revealed that MPs contribute to membrane fouling, which initially intensifies and then alleviates as coagulant concentration increases, with a turning point at 0.05 mM PAC dosage. The most significant alleviation of membrane fouling was observed at 0.2 mM PAC dosage. An in-depth analysis of interfacial interaction energy changes during filtration was conducted using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, demonstrating how MPs alter the interaction forces between foulants and the membrane surface, leading to either the exacerbation or mitigation of fouling. Additionally, it was shown that at optimal coagulant concentrations, the presence of MPs promotes the formation of a loose and porous cake layer, disrupting the original structure and creating a more open block structure, thereby alleviating membrane fouling. These findings provide valuable insights for optimizing the CUF process in microplastic-containing water treatment, presenting a novel approach to enhancing efficiency and reducing membrane fouling.

Mechanism of membrane fouling mitigation by microalgae biofilm formation for low C/N mariculture wastewater treatment: EPS characteristics, composition and interfacial interaction energy

Membrane fouling is considered one of the main limitations of membrane bioreactor (MBR) in wastewater treatment applications, including low C/N aquaculture wastewater. Although much research has focused on the integration of MBR with bacterial biofilm, there has been limited exploration into the mitigation mechanism of membrane fouling by microalgae biofilm. In this study, extracellular polymeric substances (EPS) before and after the formation of microalgae biofilm were compared, leading to the conclusion that the microalgae biofilm formation could reduce membrane fouling potential of EPS, thereby mitigating membrane fouling. EPS content and fluorescence components analysis indicated that microalgae biofilm formation could effectively reduce protein to polysaccharide ratios (PN/PS) of three types of EPS (soluble EPS (S-EPS), loosely bound EPS (LB-EPS), and tightly bound EPS (TB-EPS)), lowering the membrane fouling potential associated with protein substances, especially tryptophan-like protein. Moreover, the analysis of molecular weight (MW) suggested that microalgae biofilm could considerably decrease the MW of both S-EPS and LB-EPS, thus mitigating the influence of high MW substances on membrane fouling. Meanwhile, the precise composition of EPS revealed a reduction in hydrophobic alkanes and recalcitrant aromatics, which often lead to membrane fouling. Furthermore, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory further highlighted that microalgae biofilm weakened the interfacial interaction energy between the three EPS and membrane to mitigate membrane fouling. Therefore, this study provides a comprehensive elucidation of how microalgae biofilm formation mitigates membrane fouling, offering theoretical support for utilizing microalgae biofilm MBR in treating low C/N mariculture wastewater.

Molecular dynamics simulation of nanocellulose and cement matrix composites

The interfacial properties of nanocellulose and cement matrix are the key factors affecting the mechanical properties of composite materials. However, it is challenging to study the interface combination through conventional experiments and microscopic characterization techniques. Molecular dynamics simulation (MD), as a nanoscale analytical method, can be used to calculate and analyze the strength, deformation, destruction and interfacial interaction of materials on the atomic scale. Since the existing methods of C-S-H modeling and fiber pull-out from the matrix in molecular dynamics simulations were not suitable for cellulose/C-S-H composite models. In this paper, a molecular dynamics simulation method for nanocellulose cement matrix composites was proposed. Based on the embedded composite model, the tensile stress-strain, interfacial interaction energy, hydrogen bond, and interface failure mode were studied when cellulose was pulled out of the matrix. The results showed that adding cellulose could improve the local ductility and tensile strength of cement matrix materials. The interfacial interaction energy between cellulose and C-S-H was approximately −1.09 J/m2, which was much higher than that between carbon nanotubes and C-S-H. Cellulose would adsorb hydrogen and oxygen atoms on H2O, OH− and silica tetrahedron in C-S-H. In the pull-out simulation of cellulose in C-S-H, C-S-H on the surface of cellulose would be destroyed and attached to the cellulose surface and moved along with it, indicating that cellulose could play a good bridging role in the matrix. The simulation results revealed the action mechanism of cellulose in cement matrix materials.

Insight into the salt damage mechanism to the asphalt-aggregate interface in recycled asphalt mixtures at different salt environments using molecular dynamics and DFT simulations

In coastal areas, the complex salt environment poses new challenges to the interfacial stability and service durability of hot recycled asphalt pavements. To investigate the influence mechanism of salt environment on the adhesion properties of asphalt-aggregate interface, this study employed molecular dynamics (MD) simulation and density functional theory (DFT) to analyze the interfacial interaction energy, molecular diffusion behavior, component distribution, and molecular electrostatic property at asphalt-aggregate interface. The results show that as the content of aged asphalt increased, the interaction between asphalt and anions (Cl⁻ and SO₄²⁻) is weaker than that with cations (Na⁺, Mg²⁺ and Ca²⁺). H₂O causes the aromatics, saturates and resins to move away from the interface. Cl⁻ causes the saturates to further move away from the interface, while Na⁺ and Mg²⁺ bring the aromatics closer to the interface. Due to the greater polarity of SO₄²⁻, it moves the resins closer to the interface. With increasing aged asphalt content, the number of hydrogen bonds between asphalt and SiO₂ increases from none to some, thus enhancing the interfacial adhesion. However, this adhesion becomes more susceptible to salts. The aging effect redistributes the charge of asphalt molecules, concentrating negative potentials on the carbonyl and sulfoxide functional groups located on the outside of molecules. This increases the polarity of the asphalt molecules, making them more susceptible to salt ion attack. These findings contribute to the understanding of the adhesion properties of recycled asphalt mixtures in extreme salt environments.

Tourmaline triggered biofilm transformation: Boosting ultrafiltration efficiency and fouling resistance

Ultralow pressure filtration system, which integrates the dual functionalities of biofilm degradation and membrane filtration, has gained significant attention in water treatment due to its superior contaminant removal efficiency. However, it is a challenge to mitigate membrane biofouling while maintaining the high activity of biofilm. This study presents a novel ceramic-based ultrafiltration membrane functionalized with tourmaline nanoparticles to address this challenge. The incorporation of tourmaline nanoparticles enables the release of nutrient elements and the generation of an electric field, which enhances the biofilm activity on the membrane surface and simultaneously alleviates intrapore biofouling. The tourmaline-modified ceramic membrane (TCM) demonstrated a significant antifouling effect, with a substantial increase in water flux by 60 %. Additionally, the TCM achieved high removal efficiencies for contaminants (48.78 % in TOC, 22.28 % in UV254, and 24.42 % in TN) after 30 days of continuous operation. The fouling resistance by various constituents in natural water was individually analyzed using model compounds. The TCM with improved electronegativity and hydrophilicity exhibited superior resistance to irreversible fouling through increased electrostatic repulsion and reduced adhesion to foulants. Comprehensive characterizations and analyses, including interfacial interaction energies, redox reaction processes, and biofilm evolutions, demonstrated that the TCM can release nutrient elements to facilitate the development of functional microbial community within the biofilm, and generate reactive oxygen species (ROS) on the membrane surface to the degrade contaminants and mitigate membrane biofouling. The electric field generated by tourmaline nanoparticles can promote electron transfer in the Fe(III)/Fe(II) cycle, ensuring a stable and sustainable generation of ROS and bactericidal negative ions. These synergistic functions enhance contaminant removal and reduce irreversible fouling of the TCM. This study provides fundamental insights into the role of tourmaline-modified surfaces in enhancing membrane filtration performance and fouling resistance, inspiring the development of high-performance, anti-fouling membranes.

Effect of Mn2+ on RO membrane organic fouling: Insights into the complexation and interfacial interaction

RO process is commonly used to treat and reuse manganese-containing industrial wastewater. Nevertheless, even after undergoing multi-stage treatment, the secondary biochemical effluent still exhibits a high concentration of Mn2+ coupled with organics entering the RO system, leading to membrane fouling. In this work, we systematically analyze the RO membrane organic fouling processes and mechanisms, considering the coexistence of Mn2+ with humic acid (HA), sodium alginate (SA), bovine serum albumin (BSA) and their mixtures (HBS). The impact of Mn2+ on membrane fouling was HBS > SA > HA > BSA, controlling polysaccharide pollutant concentrations should be a priority for mitigating membrane fouling. In the presence of Mn2+ with HA, SA, or HBS, membrane fouling is primarily attributed to the complexation of organics and Mn2+ and the facilitation of interfacial interaction energy. RO membrane BSA fouling was not directly affected by Mn2+, the addition of Mn2+ induced a salting-out effect, leading to the deposition of BSA in a single molecular on the membrane. Simultaneously, adhesion energy hinders the deposition of BSA on the membrane, resulting in milder membrane fouling. This study provided the theoretical basis and suggestions for RO membrane organic fouling control in the presence of Mn2+.

Sodium disilicate pretreatment enhancing methane production from anaerobic digestion of waste activated sludge

Improving the efficiency of digestion is a major focus of waste activated sludge (WAS) anaerobic digestion (AD) research. This study investigates the viability and mechanism of sodium disilicate (SD) in enhancing the digestive efficacy of WAS. Batch AD experiments for the sludges pretreated by varied amounts of SD were carried out, and the results revealed that a dosage of 90 mmol/L resulted in the highest methane yield (247.9 mL/g·VS), marking a 90.0 % increase compared to the raw sludge. Mechanistic investigations highlighted that SD pretreatment facilitated EPS degradation, cell lysis, and modulation of interfacial interaction energy, ultimately enhancing sludge disintegration and methane generation. Microbial community analysis unveiled an enrichment of crucial functional microorganisms associated with hydrolysis, acidification, and methanation. The heightened presence of acetotrophic and hydrogenotrophic methanogens significantly boosted methane production. Furthermore, metagenomic analysis corroborated that the SD pretreatment stimulated amino acid metabolism, energy metabolism (specifically ABC transporter proteins), and carbohydrate metabolism, thereby enhancing methanogenic activity through increased microbial metabolic activities and upregulated key enzyme expression. This research underscores the potential of SD-assisted pretreatment strategies in augmenting WAS digestion, introducing supplementary pretreatment avenues for optimizing anaerobic biotechnology.

Molecular Dynamics Simulations of Gas Transport Properties in Cross-Linked Polyamide Membranes: Tracing the Morphology and Addition of Silicate Nanotubes.

This study employs molecular dynamics (MD) simulations to fundamentally provide insight into the role of cross-link density in the CO2 separation properties of interfacially polymerized polyamide (PA) membranes. For this purpose, two atomistic models of pure polyamide membranes with different cross-link densities are constructed by MD simulations to conceptually determine how the fractional free volume of polyamide affects the gas separation performance of the membrane. The PA membrane with a lower cross-link density (LCPA) shows a higher gas diffusion coefficient, a lower gas solubility coefficient, and a higher gas permeability than the PA membrane with a higher cross-link density (HCPA). Moreover, the pristine and modified silicate nanotubes (SNTs) as the fast gas transport channels are incorporated into the polyamide membranes to assess the effect of the SNT/PA interface chemistry on the CO2 separation properties of the membranes. SNTs are systematically modified by three modifying agents with different CO2-philic groups and different interfacial interaction energies with the polyamide matrix. The results of MD simulations demonstrate that the incorporation of silicate nanotubes into the PA matrix increases the gas diffusivity and permeability and decreases the CO2/gas selectivity. Moreover, the membranes containing modified SNTs possessing high CO2-philicity and high SNTs/PA interfacial interactions show a high CO2 separation performance.

The effect of gamma-ray irradiation on polymer-graphene nanocomposite interfaces

CNT yarns are used in ultra-high strength composites for use in manned deep-space vehicles. It has been previously demonstrated through experiments that gamma-ray irradiation substantially improves the mechanical performance of these composites. It is unclear how the irradiation affects the mechanical response of the CNT yarn/polymer interface that ultimately leads to these panel-level performance improvements. Physical insight into this process could enable further improvements in the CNT yarn/polymer interface design in the future. The objective of this research is to use molecular dynamics simulation to provide physical insight into the effect of gamma-ray irradiation on the mechanical behavior (interfacial interaction energy, shear resistance, adhesive strength) of the CNT yarn/polymer interface for a range of high-performance polymer systems. The simulation results indicate that gamma-ray irradiation (simulated via inclusion of defects on the CNT surface) has a most significant effect on the shear deformation resistance of CNT yarn/polymer interfaces, which likely leads to the experimentally-observed improvements in panel-level CNT yarn composites irradiated with gamma rays. The results of this study also demonstrate the importance of computational modeling in providing physical insight into observed bulk-scale material behavior. Although the predictions cannot be validated directly via experiment, such insight can ultimately lead to efficient improvements in material design (e.g. mechanical performance) that lead to further increases in panel-level composite performance.

Transcending Lifshitz Theory: Reliable Prediction of Adhesion Forces between Hydrocarbon Surfaces in Condensed Phases Using Molecular Contact Thermodynamics.

Lifshitz theory is widely used to calculate interfacial interaction energies and underpins established approaches to the interpretation of measurement data from experimental methods including the surface forces apparatus and the atomic force microscope. However, a significant limitation of Lifshitz theory is that it uses the bulk dielectric properties of the medium to predict the work of adhesion. Here, we demonstrate that a different approach, in which the interactions between molecules at surfaces and in the medium are described by a set of surface site interaction points (SSIPs), yields interaction free energies that are correlated better with experimentally determined values. The work of adhesion W(Lifshitz) between hydrocarbon surfaces was calculated in 260 liquids using Lifshitz theory and compared with interaction free energies ΔΔG calculated using the SSIP model. The predictions of these models diverge in significant ways. In particular, ΔΔG values for hydrocarbon surfaces are typically small and vary little, but in contrast, W(Lifshitz) values span 4 orders of magnitude. Moreover, the SSIP model yields significantly different ΔΔG values in some liquids for which Lifshitz theory predicts similar values of W(Lifshitz). These divergent predictions were tested using atomic force microscopy. Experimentally determined works of adhesion were closer to the values predicted using the SSIP model than Lifshitz theory. In mixtures of methanol and benzyl alcohol, even greater differences were found in the interaction energies calculated using the two models: the value of ΔΔG calculated using the SSIP model declines smoothly as the benzyl alcohol concentration increases, and values are well correlated with experimental data; however, W(Lifshitz) decreases to a minimum and then increases, reaching a larger value for benzyl alcohol than for methanol. We conclude that the SSIP model provides more reliable estimates of the work of adhesion than Lifshitz theory.

Synergistically controlling biofouling and improving membrane module permeability by using simultaneously structurally optimized and surface modified feed spacers

This study developed a new protocol to prepare feed spacers in the membrane module, by combining the optimization of spacers' geometrical parameters with subsequent chemical modification of the spacers’ surface, to enhance filtration performance comprehensively. Geometrical parameters of columnar spacers were optimized using an object-oriented and automatic optimization method based on computational fluid dynamics (CFD) simulation coupled with response surface optimization. In chemical modification, polydopamine was firstly used to provide anti-adhesive properties, followed by the even integration of silver nanoparticles (AgNPs) to exhibit antimicrobial activity. Anti-biofouling experiments involving Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria demonstrated that the combined structurally optimized and chemically modified spacers resulted in over 10 % improvement in permeate flux and a 27 % reduction in feed channel pressure (FCP) drop. Chemical modification enhanced the structural optimization resistance to flux attenuation and FCP drop increase by over 220 % and 200 %, respectively. Analysis of the anti-biofouling behavior indicated that the primary mechanism of the integrated, optimized spacers lies in the increased wall shear, bactericidal activity of AgNPs, and improved interfacial interaction energy between the spacers and foulants. This study not only developed a novel modification method for anti-biofouling spacers, but also provides in-depth understanding of the roles of modified spacers, all of which are important for their practical applications in improving membrane filtration performance.

Wettability behavior of DTMS modified SiO2: Experimental and molecular dynamics study

In this research, the wetting behavior of SiO2 modified with dodecyltrimethoxysilane (DTMS) was explored using both experimental and molecular dynamics (MD) simulation approaches. The experimental results reveal that DTMS can chemically bond to the SiO2 surface, and the contact angle (CA) reaches the maximum value of 157.7° when the mass of DTMS is twice that of SiO2. The different wetting behaviors caused by DTMS grafting were analyzed by CA fitting, ionic pairs, concentration distribution, molecule orientation, and interfacial interaction energy. The results demonstrate that a 25% DTMS grafting rate resulted in a maximum CA of 158.2°, which is ascribed to the disruption of interfacial hydrogen bonding and changes in the hydration structure caused by DTMS grafting. Moreover, the above hydrophobic SiO2 model shows a slight decrease in CA as the water temperature increases, which is consistent with the experimental findings. In contrast, an opposite change was observed for the pristine SiO2 model. Although the higher water temperature enhances the diffusion capacity of water molecules in both models, the difference in interfacial interactions is responsible for the change in CA. We hope this finding will contribute to a deeper understanding of the wetting adjustment of SiO2.

Micromechanical and chemical characteristics of interfacial transition zone in alkali-activated slag concrete containing lightweight iron-rich aggregates

This study explored the time-varying alkali-activation effects of the lightweight aggregates (LWA) on the interfacial transition zone (ITZ) of the alkali-activated slag concrete with different curing ages, molar ratios, and alkali concentrations from 28 to 300 d. The improved micromechanical performance of the ITZ at 28 d stemmed from the early-age internal curing effect of the porous LWA. However, the post-28 d internal curing effect diminished, with the alkali-activation dominating the performance of the ITZ from 28 to 300 d. Although alkali-activated cement possessed early strength characteristics, the deconvolved phase results illustrated that alkali activation persisted in the ITZ between the LWA and cement from 28 to 300 d, leading to a high proportion of calcium silica aluminate hydrate. As a marker, Fe from the lightweight iron-rich aggregates mitigated into the alkali-activated cement, demonstrating the alkali-activated reaction between the LWA and alkali-activated slag matrix. Molecular dynamics simulations further characterized that the low content of Fe did not decrease the overall strength of the ITZ. The interfacial interaction energy revealed the alkali-activation between the LWA and cement compensated for the weakening of mechanical properties caused by Fe ions on the ITZ.

Molecular dynamics study of the anticorrosive lubricating effects and interfacial behavior of dicarboxylic acid alcohol amine

In this study, water-soluble additives with excellent performance were designed, and their anticorrosive, tribological characteristics, and antibacterial properties were evaluated. Combined with molecular dynamics (MD), the interfacial behavior of additives on metal surfaces was investigated at the atomic scale. The results showed that the additive molecules could reduce the wear rate of ethylene glycol aqueous (EGaq) by 94.7 %, exhibiting excellent anticorrosive efficiency while also possessing certain antibacterial properties. MD results indicated that the additive could firmly adhere to the metal surface due to its higher electron transfer rate, and the interfacial interaction energy increased with the extension of the carbon chain. The coexistence of longer alkyl chains and frictionally active elements ensured the overall stability of the adsorption film.

Effect of side group modification on the glass transition and adhesion properties of polysiloxane at the atomic scale

Polysiloxane is a typical biomimetic dry adhesive, and polysiloxane-silica interface is a typical interface widely existing in test systems and wall-climbing robots. Studying the glass transition temperature (Tg) of polysiloxane and its adhesion properties on silica surfaces has important theoretical guiding significance and practical value for developing and applying a new generation of dry adhesion functional surfaces and devices. However, the effect of the type and content of side groups on the Tg and adhesion properties of polysiloxane is still unclear. Therefore, three side group combinations are included in the established modified polysiloxane models, with each type corresponding to five different side group contents. Molecular dynamics (MD) is used to investigate the effect of side group modification on the Tg of polysiloxane and the adhesion properties on the silica surface. The results show that, compared with polydimethylsiloxane (PDMS), introducing phenylmethyl or diphenyl into the polysiloxane increases the Tg in the studied range of side group contents. The introduction of diethyl decreases the Tg. The corresponding interfacial interactions are enhanced when the diethyl content is 2 %, 4 % and 10 %, the phenylmethyl content is 4–10 % and the diphenyl content is 2–10 %. The interfacial interactions are weakened at the unmentioned side group content. The ratio of van der Waals energy to the interfacial interaction energy is above 94.5 % in all interfaces, which means that van der Waals interaction dominates the interaction between polysiloxane and silica surface. The present model provides a deeper insight into polysiloxane, which may contribute to designing future bioinspired dry adhesives.

Modeling of the effect of the thickness of the antiferromagnetic layer on the energy of interfacial exchange interaction in Ferromagnetic/Antiferromagnet films

By means of thermodynamic and configuration averaging of the energy of the exchange interaction between the magnetic spin moments adjacent through the ferromagnetic/antiferromagnetic interphase boundary, the expression for the energy of the interphase exchange interaction Eex is obtained. The dependence of the energy Eex on the temperature and the characteristic dimensions of the ferromagnetic/antiferromagnetic two-phase film is modeled. The experimentally observed regularity of the growth of the energy of the interfacial exchange interaction due to the increase of the thickness of the antiferromagnetic layer is confirmed. A method for the estimation of the constants of the interfacial exchange interaction Jint and the exchange interaction in antiferromagnetics JAFM is proposed based on the agreement of the experimental and theoretical curves of the temperature dependence of the exchange bias field HebT.

Understanding the Interface Enhancement Mechanisms of CFRP with the Polydopamine-Polyetheramine Interphase at the Molecular Level.

In this work, polydopamine (PDA) and polyetheramine D230 were selected to construct the PDA-D230 interphase between the carbon fiber (CF) and epoxy matrix. Density functional theory (DFT) and molecular dynamics (MD) simulations were performed to explore the interface enhancement mechanisms of a carbon fiber reinforced polymer (CFRP) with the PDA-D230 interphase from the molecular level. The adsorption characteristics of a PDA molecule on the CF surface were investigated using the DFT method. The results show that stronger π-π stacking interactions are formed due to the structure and orientation preference of the PDA molecule. The interfacial structures and properties of CFRP with the PDA-D230 interphase are derived from MD simulations. The PDA-D230 interphase on the CF surface induces stronger interfacial interaction energy, leading to the better load transfer between the CF and epoxy matrix. The existence of the PDA-D230 interphase on the CF surface can decrease the mean-square displacement (MSD) value and the free volume fraction of CFRP, which restricts the movement of epoxy atoms and inhibits the translational and rotational motion of epoxy chains. Compared with the epoxy using pristine CFs as reinforcement, the interfacial shear stress (ISS) of CFRP with the PDA-D230 interphase is improved by 13.1%. Our results provide valuable insights into the interface characteristics of CFRP with the PDA-D230 interphase, which are of great significance for exploring the strengthening mechanisms for CFRPs with the PDA-D230 interphase.