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Background: During the dissolution of amorphous solid dispersion (ASD) formulations, the drug load (DL) often impacts the release mechanism and the occurrence of loss of release (LoR). The ASD/water interfacial gel layer and its specific phase behavior in connection with DL strongly dictate the release mechanism and LoR of ASDs, as reported in the literature. Thermodynamically driven liquid-liquid phase separation (LLPS) and/or drug crystallization at the interface are the key phase transformations that drive LoR. Methods: In this study, a combination of Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) thermodynamic modeling and in silico molecular simulation was applied to investigate the release mechanism and the occurrence LoR of an ASD formulation consisting of ritonavir as the active pharmaceutical ingredient (API) and the polymer, polyvinylpyrrolidone-co-vinyl acetate (PVPVA64). A thermodynamically modeled ternary phase diagram of ritonavir (PVPVA64) and water was applied to predict DL-dependent LLPS in the ASD/water interfacial gel layer. Microscopic Erosion Time Testing (METT) was used to experimentally validate the phase diagram predictions. Additionally, in silico molecular simulation was applied to provide further insights into the phase separation, the release mechanism, and aggregation behavior on a molecular level. Results: Thermodynamic modeling, molecular simulation, and experimental results were consistent and complementary, providing evidence that ASD/water interactions and phase separation are essential factors driving the dissolution behavior and LoR at 40 wt% DL of the investigated ritonavir/PVPVA64 ASD system, consistent with previous studies. Conclusions: This study provides insights into the potential of blending thermodynamic modeling, molecular simulation, and experimental research to comprehensively understand ASD formulations. Such a combined approach can be leveraged as a computational framework to gain insights into the ASD dissolution mechanism, thereby facilitating in silico screening, designing, and optimization of formulations with the benefit of significantly reducing the number of experimental tests. [ABSTRACT FROM AUTHOR]

Dissipative particle dynamics (DPD) simulations is used to study the effect of Am/2BmAm/2 and H-shaped (Am/4)2Bm(Am/4)2 block copolymers on the interfacial properties of ternary blends. Our simulations show the following: (i) The capacity of block copolymers to diminish interfacial tension is closely linked to their compositions. With identical molecular weights and concentrations, H-shaped block copolymers outperform triblock copolymers in mitigating interfacial tension. (ii) The interfacial tension within the blends correlates positively with the escalation in H-shaped block copolymer molecular weight. This correlation suggests that H-shaped block copolymers featuring a low molecular weight demonstrate superior efficacy as compatibilizers when contrasted with those possessing a high molecular weight. (iii) Enhancing the concentration of H-shaped block copolymers fosters their accumulation at the interface, leading to a reduction in correlations between immiscible homopolymers and a consequent decrease in interfacial tension. (iv) As the length of the homopolymer chains increases, there is a concurrent elevation in interfacial tension, suggesting that H-shaped block copolymers perform more effectively as compatibilizers in blends characterized by shorter homopolymer chain lengths. These findings elucidate the associations between the efficacy of H-shaped block copolymer compatibilizers and their specific molecular characteristics. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) ink is a primary type of ink used in additive manufacturing with 3D inkjet printing. However, ink aggregation presents a challenge in nano-inkjet printing, affecting the stability and quality of the printing fluid and potentially leading to the clogging of nanometer-sized nozzles. This paper utilizes a Dissipative Particle Dynamics (DPD) simulation to investigate the aggregation behavior of alumina in a blend of 1,6-Hexanediol diacrylate (HDDA) and Trimethylolpropane triacrylate (TMPTA). By analyzing the effects of solid content, polymer component ratios, and dispersant concentration on alumina aggregation, the optimal ink formulation was identified. Compared to traditional experimental methods, DPD simulations not only reduce experimental costs and time but also reveal particle aggregation mechanisms that are difficult to explore through experimental methods, providing a crucial theoretical basis for optimizing ink formulations. This study demonstrates that alumina ceramic ink achieves optimal performance with a solid content of 20%, an HDDA-to-TMPTA ratio of 4:1, and 9% oleic acid as a dispersant. [ABSTRACT FROM AUTHOR]

Triblock copolymers such as styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) have been widely used as an anion exchange membrane for fuel cells due to their phase separation properties. However, modifying the polymer architecture for optimized membrane properties is still challenging. This research develops a strategy to control the membrane morphology based on quaternized SEBS (SEBS-Q) by dual-tapering the interfacial block sequences. The structural and transport properties of SEBS-Q with various tapering styles at different hydration levels are systematically investigated by coarse-grained molecular simulations. The results show that the introduction of the tapered regions induces the formation of a bicontinuous water domain and promotes the diffusivity of the mobile components. The interplay between the solvation of the quaternary groups and the tapered fraction determines the conformation of polymer chains among the hydrophobic–hydrophilic subdomains. The strategy presented here provides a new path to fabricating fuel cell membranes with controlled microstructures. [ABSTRACT FROM AUTHOR]

An automated pipeline for comprehensive calculation of intermolecular interaction energies based on molecular force-fields using the Tinker molecular modelling package is presented. Starting with non-optimized chemically intuitive monomer structures, the pipeline allows the approximation of global minimum energy monomers and dimers, configuration sampling for various monomer–monomer distances, estimation of coordination numbers by molecular dynamics simulations, and the evaluation of differential pair interaction energies. The latter are used to derive Flory–Huggins parameters and isotropic particle–particle repulsions for Dissipative Particle Dynamics (DPD). The computational results for force fields MM3, MMFF94, OPLS-AA and AMOEBA09 are analyzed with Density Functional Theory (DFT) calculations and DPD simulations for a mixture of the non-ionic polyoxyethylene alkyl ether surfactant C10E4 with water to demonstrate the usefulness of the approach. Scientific Contribution To our knowledge, there is currently no open computational pipeline for differential pair interaction energies at all. This work aims to contribute an (at least academically available, open) approach based on molecular force fields that provides a robust and efficient computational scheme for their automated calculation for small to medium-sized (organic) molecular dimers. The usefulness of the proposed new calculation scheme is demonstrated for the generation of mesoscopic particles with their mutual repulsive interactions. [ABSTRACT FROM AUTHOR]

Spatial gradient materials occupy an important research position in the field of functional materials with their unique porous structure. Gradient changes in pore size and density distribution have received extensive attention in the fields of biomimetic and smart materials. The gradient transition law is mathematically related to the driving force of isomerization reaction and component phase separation. In this study, a dissipative particle dynamics simulation is used to introduce photoisomerization reactions into the system. Lambert's law is used to construct a reaction model for the variation of light intensity with irradiation depth, and a gradient structure with a spatial transition law is obtained. The effects of the extinction coefficient ε, the initial reaction probability Pr0, and the interactions α(A,B) between the isomerized molecules as well as the viscosity on the formation of the gradient structure are investigated in detail. Furthermore, the mathematical proportionality between the size of the phase region and interfacial energy of the two phases is elucidated. This study provides preliminary computational insights into the factors affecting the photoinduced phase separation process of polymeric gradient materials. It may help to develop effective strategies to improve the phase separation and properties of polymer gradient materials in subsequent studies. [ABSTRACT FROM AUTHOR]

The complete description of energy and material transport within the Generalized energy-conserving dissipative particle dynamics with mass transfer (GenDPDE-M) methodology is presented. In particular, the dynamic coupling between mass and energy is incorporated into the GenDPDE-M, which was previously introduced with dynamically decoupled fluxes (J. Bonet Avalos et al., J. Chem. Theory Comput., 18 (12): 7639–7652, 2022). From a theoretical perspective, we have derived the appropriate Fluctuation-Dissipation theorems along with Onsager's reciprocal relations, suitable for mesoscale models featuring this coupling. Equilibrium and non-equilibrium simulations are performed to demonstrate the internal thermodynamic consistency of the method, as well as the ability to capture the Ludwig–Soret effect, and tune its strength through the mesoscopic parameters. In view of the completeness of the presented approach, GenDPDE-M is the most general Lagrangian method to deal with complex fluids and systems at the mesoscale, where thermal agitation is relevant. [ABSTRACT FROM AUTHOR]

Despite huge effort over the years, the design of functionalised nanocarriers (NCs) for targeted drug delivery to endothelial cells is still to be completely unveiled. Dissipative particle dynamics (DPD) simulation is used to study the adhesion of NCs to endothelial cells under the influence of series of parameters such as shape, size, and ligand density of the NCs. However, preparing a performance space mapping that illustrates the penetration depths of NCs as a function of variations in their properties requires simulations of all possible NCs with the above-mentioned properties, which is not feasible. This challenge was addressed by leveraging a Gaussian process regression (GPR)-informed active learning strategy and an extensive exploration of numerous samples, each representing different properties of NCs. The performance space mapping reveals that NCs with rod and disc shapes exhibit superior penetration capabilities compared to those with a spherical shape. Furthermore, it demonstrates that smaller-sized rod-shaped NCs and larger-sized disc-shaped NCs tend to achieve better penetration. When considering smaller NCs, the influence of ligand density appears to be limited. On the contrary, for larger NCs, an increase in ligand density correlates with greater penetration depth, underscoring its substantial role in shaping their penetration capabilities. [ABSTRACT FROM AUTHOR]

Crude oil desalination and dehydration are necessary for storage, transportation, and processing procedures. However, the behaviour of fine emulsion droplets under an electric field has always been questioned. This paper modified the dissipative particle dynamics method (DPD) to study the deformation process of fine emulsion droplets under a high-strength electric field. Compared with the literature data, the reliability of the DPD method is confirmed. The influence of the crude oil properties and the electric field characteristics on the behaviour of the emulsion droplet was analysed, and the effect factors included electric field intensity, electric field frequency, emulsion droplet size, centre distance ratio, conservative force intensity, dissipative strength, and crude oil density. The relationship between critical electric field intensity and emulsion droplet deformation was formulated based on the simulational dates. [ABSTRACT FROM AUTHOR]

Lignin, a renewable aromatic polymer, has great potential as a synthetic building block for functional materials. The effects of quaternary ammonic methylation of alkali lignin (AL) on the morphologies and ofloxacin antibiotic (OA) removal application from water are investigated by using the dissipative particle dynamics (DPD) simulation method. Untreated AL can form spherical aggregates, but the phenylpropane units of untreated AL and loaded broad‐spectrum OA molecules are randomly distributed in aggregates. However, if quaternary ammonic groups are grafted onto all orthopositions of the phenolic hydroxyl groups (100‐QAMAL), then multilamellar spherical aggregates are obtained and OA molecules are entrapped in the aggregates. To prepare multilamellar spherical aggregates with an ordered and regular layered structure, <15 v% of 100‐QAMAL and low molecular weights of AL (≈4700–9400 Da) are suggested to be used. Lignin‐based multilamellar spherical aggregates can be adopted as potential functional carriers for removing pollutant OA from water. [ABSTRACT FROM AUTHOR]

To enhance the mechanical properties of the Nitrate Ester Plasticized Polyether solid propellant matrix, the uniaxial tension of multi-component systems is simulated and the factors influencing the mechanical properties of the propellant matrix are investigated. First, mesoscale models of five types of systems include poly alpha olefin (PAO(3)), polyethylene glycol (PEG200, PEG400, PEG600), and 1,4-butanediol (BDO) are established, followed by uniaxial tensile simulations. The results show PEG600, PEG400, PEG200, BDO, and PAO(3) in order of enhancing the mechanical performance of the matrix. Second, the diffusion behavior of nitroglycerin (NG) and butanetriol trinitrate (BTTN) in various systems is investigated. The results show that NG exhibits higher diffusion capacity than BTTN, and the diffusion coefficient increases with an increment in the molecular weight of PEG. Additionally, the influence of different plasticizer ratios (2.8–3.0), curing parameters (1.58–1.62), and chain extension parameters (0.08–0.10) on the mechanical properties of the PEG600 system are investigated. The results demonstrate that as the plasticizer ratio increases, there is a gradual decrease in the modulus of the matrix. Additionally, an increase in the curing parameter leads to a substantial enhancement in the tensile strength of the matrix, while increasing the chain extension parameter significantly expands the maximum tensile length of the matrix. Finally, employing the Slip-Spring model, the effects of the physical and chemical cross-linked network of the propellant are simulated. The result shows that increasing the content of a chemical cross-linked network significantly improves the tensile strength of the matrix.

This study investigates the self-assembly and phase transitions of cholesteric liquid crystals (CLCs) when confined in nanotubes, specifically focusing on the variations in their molecular structures. A dissipative particle dynamics method was used to investigate how the changes in helix radius (${r_{{\rm{LC}}}}$ r LC ) and pitch ($P$ P) affect the behaviour of the LCs. For pitches of 24, 12, and 6, the orientation order parameter (${P_2}$ P 2 ) showed distinct trends during cooling. Smaller helix radii resulted in isotropic to nematic to smectic phase transitions, whereas larger radii resulted in a novel smectic phase with spiral structures (Sm $_{\rm{s}}$ s ). Circumferential local-order parameters (${P_{2r}}$ P 2 r and ${P_{2z}}$ P 2 z ) were introduced to better characterise the phases, and a disordered spiral-structure phase (Sm $_{{\rm{s}}2}$ s 2 ) with local perturbations was observed. The transitions between isotropic, nematic, and smectic phases, highlighting the influence of the pitch and helix radius, were observed from the phase diagrams. Smaller pitches and radii prevented the formation of stable structures; however, specific combinations induced characteristic spiral structures in the smectic phase. These results provide new insights into the self-assembly of confined CLCs, which have potential applications in the design of photonic devices and LC-based sensors. This study advances our understanding of phase control in quasi-one-dimensional systems and highlights the importance of molecular variations in liquid crystal behaviour. [ABSTRACT FROM AUTHOR]

The dissipative particle dynamics (DPD) simulation was used to study the morphologies and structures of the paclitaxel‐loaded PLA‐b‐PEO‐b‐PLA polymeric micelle. We focused on the influences of PLA block length, PLA‐b‐PEO‐b‐PLA copolymer concentration, paclitaxel drug content on morphologies and structures of the micelle. Our simulations show that: (i) with the PLA block length increase, the self‐assemble structure of PLA‐b‐PEO‐b‐PLA copolymers with paclitaxel vary between onion‐like structure (core‐middle layer‐shell) to spherical core‐shell structure. The PEO shell thins and the size of the PLA core increases. The onionlike structures are comprised of the PEO hydrophilic core, the PLA hydrophobic middle layer, and the PEO hydrophilic shell, the distribution of the paclitaxel drug predominantly occurs within the hydrophobic intermediate layer; (ii) The system forms a spherical core‐shell structure when a small amount of the drug is added, and within a certain range, the size of the spherical structure increases as the drug amount increases. When the drug contents (volume fraction) cdrug = 10%, it can be observed that the PLA4‐b‐PEO19‐b‐PLA4 spherical structures connect to form rod‐shaped structures. With the length of PLA block NPLA = 8, as the paclitaxel drug concentrations cdrug = 4%, PEO has been insufficient to completely encapsulate the PLA and paclitaxel drug beads. To enhance drug loading capacity while maintaining stability of the system in aqueous solution, the optimal composition for loading paclitaxel is PLA4‐b‐PEO19‐b‐PLA4; the drug content is not higher than 4%; (iii) The paclitaxel‐loaded PLA4‐b‐PEO19‐b‐PLA4 micelle undergo the transition from onionlike (core‐middle layer‐shell) to spherical (core‐shell) to rod‐shaped and lamellar structure as the PLA4‐b‐PEO19‐b‐PLA4 copolymer concentration increases from ccp = 10% to 40%. [ABSTRACT FROM AUTHOR]

Understanding properties of materials at the molecular level are crucial to develop novel nano-carriers for the purpose of drug delivery. To that purpose, we perform mesoscopic simulations to study the formation mechanism and properties of lecithin liposomes encapsulating coenzyme Q10. The self-assembly process of the liposomes is monitored as well as the structural properties such as RDFs, Voronoi volumes and vesicle sizes. We found that increasing the concentration of lecithin leads to increasing vesicles size, but similar total Voronoi volumes and a decrease in the interactions between liposome and coenzyme Q10 as the number of lecithin molecules increase in solution. Moreover, steered MD simulations are performed to estimate the strength of interactions between encapsulated material and liposomes by applying a mechanical force to coenzyme Q10 beads. The computed values are observed to not to be influenced by the lecithin concentration. Finally, the computed radial density and pressure profiles indicate that the liposomal bilayer is quite homogenous in density, but exhibit interfacial pressure excess, which drives the bilayer to form spherical liposomal vesicles. The release properties of coenzyme Q10 are characterized and found that the Weibull's model is able to represent the release character as a result of the mechanical force. Our findings in this work would hopefully stimulate a better understanding of liposomal systems while introducing new computational tools to study properties of these materials. [ABSTRACT FROM AUTHOR]

AbstractThe study of emulsion stabilization mechanisms is of great importance in the field of crude oil extraction, transportation and processing. In order to further investigate the roles of asphaltenes and surfactants in the emulsion stabilization process, the adsorption mechanisms of asphaltenes and surfactants at the oil-water interface were investigated using dissipative particle dynamics. The results show that: the asphaltene interfacial film gradually becomes thicker before the saturation adsorption of asphaltene molecules at the oil-water interface, and the interfacial tension decreases with the increase of the number of molecules until it reaches the equilibrium state; different surfactant molecules have different influences on the interface, and the calculations of the radial distribution function and the interfacial tension show that H2T4 molecules have a stronger effect than H4T4 at the oil-water interface and have stronger surface activity. H2T4 reaches saturation adsorption capacity faster than H4T4 and has higher interfacial efficiency. The asphaltene-surfactant composite system can stabilize the oil-water interface more effectively. Competitive and synergistic effects of asphaltene and surfactant in the process of interfacial adsorption. When the concentration of surfactant in the composite system is low, there is a synergistic effect between the two in the interfacial adsorption process; when the concentration of surfactant is high, there is a competitive effect between the two in the synergistic adsorption process. The surfactant H4T4 has both interfacial adsorption and self-aggregation in the competitive adsorption process. This paper provides ideas for exploring the kinematic laws of molecular behavior in the stabilization mechanism of crude oil emulsions. [ABSTRACT FROM AUTHOR]

Y-shaped polymer brushes represent a special class of binary mixed polymer brushes, in which a combination of different homopolymers leads to unique phase behavior. While most theoretical and simulation studies use monodisperse models, experimental systems are always polydisperse. This discrepancy hampers linking theoretical and experimental results. In this theoretical study, we employed dissipative particle dynamics to study the influence of polydispersity on the phase behavior of Y-shaped brushes grafted to flat surfaces under good solvent conditions. Polydispersity was kept within experimentally achievable values and was modeled via Schulz–Zimm distribution. In total, 10 systems were considered, thus covering the phase behavior of monodisperse, partially polydisperse and fully polydisperse systems. Using such generic representation of real polymers, we observed a rippled structure and aggregates in monodisperse systems. In addition, polydisperse brushes formed a stable perforated layer not observed previously in monodisperse studies, and influenced the stability of the remaining phases. Although the perforated layer was experimentally observed under good solvent conditions and in the melt state, further confirmation of its presence in systems under good solvent conditions required mapping real polymers onto mesoscale models that reflected, for example, different polymer rigidity, and excluded volume effects or direct influence of the surface, just to mention a few parameters. Finally, in this work, we show that mesoscale modeling successfully describes polydisperse models, which opens the way for rapid exploring of complex systems such as polydisperse Y-shaped brushes in selective or bad solvents or under non-equilibrium conditions. [ABSTRACT FROM AUTHOR]

Shape-memory polyurethanes (SMPUs) are promising materials that change shape in response to external heat. These polymers have a dual-segment structure: a hard segment for netpoint and a soft segment for molecular switch. Understanding the molecular behavior of each segment and microphase-separated morphology is crucial for comprehending the shape-memory mechanism. This study aimed to understand the shape-memory behavior by observing the phase separation of SMPU using mesoscale models based on dissipative particle dynamics (DPD) simulations. The SMPU copolymer was modeled using 4,4′-diphenylmethane diisocyanate (MDI, hard segment) and poly(ethylene oxide) (PEO, soft segment). By calculating segment solubility and repulsion parameters, we found that the hard-segment domain changes from isolated form to a lamellar and interconnected structure and eventually to a continuous form as its content increases. Combining these insights with shape-memory performance models can enhance our understanding of better SMPU design and contribute significantly to the optimization of smart stimuli-responsive materials.

This publication continues the cycle of our work aimed at improving the methodology for constructing mesoscale models of network polymers and characterizing their physical properties. As the object of study, the epoxy resin of bisphenol A, diglycidyl ether, and a tricarboxylic fatty acid hardener was chosen. Its structure is the result of three parallel reactions. For their correct reproduction, an algorithm was proposed, which allows to take into account the peculiarities of the relationship of all ongoing processes. The system model was constructed by mapping the chemical structure of the monomers onto an equivalent mesoscale representation. It was used to study the relationship between the structure and mechanical properties of feeding networks as a function of the ratio of volume fractions of comonomers in the initial reaction mixture. All calculations were performed within the reaction version of the dissipative particle dynamics method. The structure of polymer networks in the constructed samples was characterized by topological analysis. The study of mechanical properties was carried out by constructing the "stress-strain" dependencies. The results obtained show a good correlation between the density of the load-bearing chains and the mechanical properties of the resulting networks. It is shown that the material samples with the highest degree of transformation and the density of the number of load-bearing chains have the highest stiffness.

Dissipative particle dynamics (DPD) simulations is used to study the effect of Am/2BmAm/2 and H-shaped (Am/4)2Bm(Am/4)2 block copolymers on the interfacial properties of ternary blends. Our simulations show the following: (i) The capacity of block copolymers to diminish interfacial tension is closely linked to their compositions. With identical molecular weights and concentrations, H-shaped block copolymers outperform triblock copolymers in mitigating interfacial tension. (ii) The interfacial tension within the blends correlates positively with the escalation in H-shaped block copolymer molecular weight. This correlation suggests that H-shaped block copolymers featuring a low molecular weight demonstrate superior efficacy as compatibilizers when contrasted with those possessing a high molecular weight. (iii) Enhancing the concentration of H-shaped block copolymers fosters their accumulation at the interface, leading to a reduction in correlations between immiscible homopolymers and a consequent decrease in interfacial tension. (iv) As the length of the homopolymer chains increases, there is a concurrent elevation in interfacial tension, suggesting that H-shaped block copolymers perform more effectively as compatibilizers in blends characterized by shorter homopolymer chain lengths. These findings elucidate the associations between the efficacy of H-shaped block copolymer compatibilizers and their specific molecular characteristics.

Ultraviolet (UV) ink is a primary type of ink used in additive manufacturing with 3D inkjet printing. However, ink aggregation presents a challenge in nano-inkjet printing, affecting the stability and quality of the printing fluid and potentially leading to the clogging of nanometer-sized nozzles. This paper utilizes a Dissipative Particle Dynamics (DPD) simulation to investigate the aggregation behavior of alumina in a blend of 1,6-Hexanediol diacrylate (HDDA) and Trimethylolpropane triacrylate (TMPTA). By analyzing the effects of solid content, polymer component ratios, and dispersant concentration on alumina aggregation, the optimal ink formulation was identified. Compared to traditional experimental methods, DPD simulations not only reduce experimental costs and time but also reveal particle aggregation mechanisms that are difficult to explore through experimental methods, providing a crucial theoretical basis for optimizing ink formulations. This study demonstrates that alumina ceramic ink achieves optimal performance with a solid content of 20%, an HDDA-to-TMPTA ratio of 4:1, and 9% oleic acid as a dispersant.

Self-assembly of surfactants into complex structures is key to the performance of many formulated products, which form a significant fraction of the world’s manufactured goods. Here we adopt the dissipative particle dynamics simulation approach to explore the self-assembly process of surfactants, with the aim of understanding what information can be obtained that may correlate with an increased zero-shear viscosity of surfactant based products. To this end we experimentally measured the zero-shear viscosity of mixed micelle systems comprised of cocoamidopropyl betaine (CAPB) and sodium lauryl sarcosinate (SLSar), as a function of the CAPB/SLSar mass ratio and pH, and characterised the early stages of self-assembly of the same systems computationally. From simulation we identify three distinct behaviors in the micellar self-assembly process (logarithmic, linear and cubic growth) which we find show some degree of correlation with the experimental zero-shear viscosity. Owing to the relatively short simulation times required, this may provide formulation scientists with a practical route to identify regions of interest (i. e. those with a desired zero-shear viscosity) prior to synthesising de novo (potentially natural) surfactants. [ABSTRACT FROM AUTHOR]

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The commercialized lithium‐ion battery separators are mass‐produced by mixing ultra‐high molecular weight polyethylene (UHMWPE) and paraffin oil (PO). The dissipative particle dynamics method is utilized to investigate the extrinsic factors (shear rate and cooling rate) and the intrinsic factors (the molecular chain length) on the microstructure of the UHMWPE‐PO mixture. For the mixture with UHMWPE possessing the same chain length, the high shear rate promoted a lower porosity (~28%) and smaller pores. In contrast, the slow shearing led to a high porosity (~40%) and larger pores. For the mixture with UHMWPE possessing short and long chains, the shear rate hardly affects the porosity and the pore size: the porosity was kept at ~30%, and the pore size was reduced by ~35% compared to the model with the same‐chain‐length UHMWPE. The cooling rate after shearing is the dominant factor in determining the porosity and pore size: the fast cooling raised the porosity by ~33% but hardly increased the pore size, while the slow cooling raised the porosity by ~74%, and the pore size by ~105%. The current study provided a deep understanding of the pore structure evolution in separator processing. Highlights: The effects of processing parameters on the pore structures are numerically illustrated.MD simulation and rheometer measurement assist DPD interaction parameters calibration for UHMWPE and PO.The low shear rate leads to a higher porosity and pore size.At the high shear rate, short UHMWPE chains reduce porosity but do not increase pore size.The fast‐cooling process slightly increases the porosity while keeping the pore size. [ABSTRACT FROM AUTHOR]

With the advancement of oilfield extraction technology, since oil-water emulsions in waxy crude oil are prone to be deposited on the pipe wall, increasing the difficulty of crude oil extraction. In this paper, the mesoscopic dissipative particle dynamics method is used to study the mechanism of the crystallization and deposition adsorbed on the wall. The results show that in the absence of water molecules, the paraffin molecules near the substrate are deposited on the metallic surface with a horizontal morphology, while the paraffin molecules close to the fluid side are arranged in a vertical column morphology. In the emulsified system, more water molecules will be absorbed on the metallic substrate than paraffin molecules, which obstructed the direct interaction between paraffin molecules and solid surface. Therefore, the addition of water molecules hinders the crystallization of wax near the substrate. Perversely, on the fluid side, water molecules promote the formation of paraffin crystallization. The research in this paper reveals the crystallization mechanism of paraffin wax in oil-water emulsions in the pipeline from the microscopic scale, which provides theoretical support for improving the recovery of wax-containing crude oil and enhancing the transport efficiency. [ABSTRACT FROM AUTHOR]

In this research, we have used the dissipative particle dynamics (DPD), a mesoscopic simulation technique, in order to investigate the dynamics of lipid domains in near critical temperature. Our specific focus has been on exploring the influence of lipid domain size on its lifetime, which mimics the behavior of lipid rafts within cellular membranes. The lipid membranes used in this study were composed of saturated and unsaturated lipids, which have been immersed in water. Through the simulation of these membranes close to their critical temperature, we have successfully generated fluctuating domains that mimic the lipid rafts observed in cellular systems. We have proposed a method to obtain the lifetime of the fluctuating domains by analyzing the sizes of the lipid domains at specific intervals of time. Our investigations have revealed a linear correlation between the initial size of the lipid domain and its lifetime. Our research finding give an insight into the underlying mechanisms that govern lipid rafts and their vital role in various cellular processes.

Triblock copolymers such as styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) have been widely used as an anion exchange membrane for fuel cells due to their phase separation properties. However, modifying the polymer architecture for optimized membrane properties is still challenging. This research develops a strategy to control the membrane morphology based on quaternized SEBS (SEBS-Q) by dual-tapering the interfacial block sequences. The structural and transport properties of SEBS-Q with various tapering styles at different hydration levels are systematically investigated by coarse-grained molecular simulations. The results show that the introduction of the tapered regions induces the formation of a bicontinuous water domain and promotes the diffusivity of the mobile components. The interplay between the solvation of the quaternary groups and the tapered fraction determines the conformation of polymer chains among the hydrophobic–hydrophilic subdomains. The strategy presented here provides a new path to fabricating fuel cell membranes with controlled microstructures.

Self-assembly of surfactants into complex structures is key to the performance of many formulated products, which form a significant fraction of the world’s manufactured goods. Here we adopt the dissipative particle dynamics simulation approach to explore the self-assembly process of surfactants, with the aim of understanding what information can be obtained that may correlate with an increased zero-shear viscosity of surfactant based products. To this end we experimentally measured the zero-shear viscosity of mixed micelle systems comprised of cocoamidopropyl betaine (CAPB) and sodium lauryl sarcosinate (SLSar), as a function of the CAPB/SLSar mass ratio and pH, and characterised the early stages of self-assembly of the same systems computationally. From simulation we identify three distinct behaviors in the micellar self-assembly process (logarithmic, linear and cubic growth) which we find show some degree of correlation with the experimental zero-shear viscosity. Owing to the relatively short simulation times required, this may provide formulation scientists with a practical route to identify regions of interest (i. e. those with a desired zero-shear viscosity) prior to synthesising de novo (potentially natural) surfactants.

Although the behavior of the confined semi-dilute solutions of self-assembling copolymers represents an important topic of basic and applied research, it has eluded the interest of scientists. Extensive series of dissipative particle dynamics simulations have been performed on semi-dilute solutions of A5B5 chains in a selective solvent for A in slits using a DL-MESO simulation package. Simulations of corresponding bulk systems were performed for comparison. This study shows that the associates in the semi-dilute bulk solutions are partly structurally organized. Mild steric constraints in slits with non-attractive walls hardly affect the size of the associates, but they promote their structural arrangement in layers parallel to the slit walls. Attractive walls noticeably affect the association process. In slits with mildly attractive walls, the adsorption competes with the association process. At elevated concentrations, the associates start to form in wide slits when the walls are sparsely covered by separated associates, and the association process prevents the full coverage of the surface. In slits with strongly attractive walls, adsorption is the dominant behavior. The associates form in wide slits at elevated concentrations only after the walls are completely and continuously covered by the adsorbed chains. [ABSTRACT FROM AUTHOR]

A hexameric quaternary ammonium salt surfactant Tz-6C12QC featuring a rigid triazine spacer and six ammonium groups was synthesized. The molecular structure and aggregation behavior of Tz-6C12QC were characterized by nuclear magnetic resonance spectroscopy, surface tension, conductivity, dynamic light scattering, and transmission electron microscopy, etc. Dissipative particle dynamics (DPD) simulation was employed to investigate the self-assembly behavior of Tz-6C12QC at different concentrations. The rheological behavior of the polyacrylamide/Tz-6C12QC system was characterized by shear rheology. The results indicated that Tz-6C12QC exhibited superior surface activity and lower surface tension compared to conventional surfactants. Rheology analysis revealed that Tz-6C12QC had a significant viscosity reduction effect on polyacrylamide. DLS and TEM indicated that, as the concentration of Tz-6C12QC increased, monomer associations, spherical aggregations, vesicles, tubular micelles, and bilayer vesicles were sequentially formed in the solution. This study presents a synthetic approach for polysurfactants with a rigid spacer and sheds light on the self-assembly process of micelles. [ABSTRACT FROM AUTHOR]

Poly(aryl ether sulfone ketone) (PPESK) is an engineering plastic with high strength, good heat resistance, insulation, and chemical corrosion resistance. The properties of PPESK fiber prepared by centrifugal melt electrospinning can be improved, and the method is efficient and environmentally friendly. This article employs a systematic analysis to investigate the impact of process parameters on the jet formation process, jet motion, fiber diameter, fiber yield, and changes in molecular chain orientation of PPESK. The analysis uses dissipative particle dynamics simulation to reveal that PPESK fibers can attain a certain degree of refinement, and fiber yield can be increased with an appropriate increase in rotational speed, temperature, and electric field force. Moreover, for PPESK with different chain lengths, longer molecular chains impede the untwisting of the molecular chains within the fiber, weakening the fiber orientation, increasing fiber diameter, and resulting in a slower fiber yield increase. These simulation results provide theoretical guidance for preparing PPESK ultrafine fibers with the required performance, shortening the exploration process of actual spinning, and saving time and labor. [ABSTRACT FROM AUTHOR]

The suitability of dissipative particle dynamics simulations is investigated to predict the dynamics of polymer chains in dilute polymer solutions. The authors find that the predictions depend on the value of the repulsive parameter for bead‐bead pairwise interactions used in the DPD simulations (aij). For all systems, the chain sizes and the relaxation time spectrum are analyzed. For aij = 0, theta solvent behaviour is obtained, whereas the dynamics at equilibrium agrees well with the predictions of the Zimm model. For higher values of aij, the static properties of the chain show good solvent behaviour. However, the scaling laws for the chain dynamics at equilibrium show wide variations, with consistent results obtained only at an intermediate value of aij = 25. At higher values of the repulsive parameter (aij ⩾ 25), the simulations are also able to predict the abrupt cut‐off in the relaxation spectrum, which has been observed earlier in experiments of dilute solutions. To verify further, the chain dynamics in shear flow using DPD simulations is studied. Specifically, the variation of the chain is analysed stretch and end‐over‐end tumbling with shear rates. Overall, the trends obtained from DPD simulations agree well with those observed in earlier BD simulations. [ABSTRACT FROM AUTHOR]

Dissipative particle dynamics (DPD) with bond uncrossability shows a great potential in studying entangled polymers, however relatively little is known of applicability range of entangled DPD model to be use as a model for ideal chains and properly describe the full dynamics of entangled melts. Therefore, we perform a comprehensive study on structure, dynamics and linear viscoelasticity of a typical DPD entangled model system, semiflexible linear polymer melt. These polymers obey Flory's ideality hypothesis in chain dimensions, but their local structure exhibits nonideal behavior due to weak correlated hole effect. Both monomer motion and viscoelasticity relaxation reproduce the full pictures as predicted by reptation theory. The stronger chain length dependent diffusion coefficient and relaxation time as well as dynamic moduli are in close agreement with predictions of modern tube model that accounts for additional relaxation mechanisms besides chain reptation. However, an anomalous sub-diffusive center of mass motion is observed both before and after the intermediate reptation regime and the cross-correlation between chains is not negligible even these polymers obey stress-optical law, indicating limitations of the reptation theory. Hence semiflexible linear entangled DPD model can correctly describe statics and dynamics of entangled polymer melts. [ABSTRACT FROM AUTHOR]

The reaction of a biphasic catalysis with microgels bearing catalytic groups adsorbed at liquid interface was simulated for the first time using dissipative particle dynamics. It was shown that the rate of the catalytic process increases with the degree of deformation of the polymer network, which depends on the fraction of the crosslinker and the solubility of the polymer in both phases. It was found that the highest reaction rate was observed when the microgel was soluble in both phases due to an increase in its porosity (in comparison with amphiphilic microgels) and in the water–microgel–oil contact area with a simultaneous decrease in the time for the reagents to reach the catalytic groups due to the flattening of the microgel. The results obtained can be useful for increasing the efficiency of a wide range of catalytic reactions of the type considered through the use of network-like macromolecules. [ABSTRACT FROM AUTHOR]

Y-shaped polymer brushes represent a special class of binary mixed polymer brushes, in which a combination of different homopolymers leads to unique phase behavior. While most theoretical and simulation studies use monodisperse models, experimental systems are always polydisperse. This discrepancy hampers linking theoretical and experimental results. In this theoretical study, we employed dissipative particle dynamics to study the influence of polydispersity on the phase behavior of Y-shaped brushes grafted to flat surfaces under good solvent conditions. Polydispersity was kept within experimentally achievable values and was modeled via Schulz–Zimm distribution. In total, 10 systems were considered, thus covering the phase behavior of monodisperse, partially polydisperse and fully polydisperse systems. Using such generic representation of real polymers, we observed a rippled structure and aggregates in monodisperse systems. In addition, polydisperse brushes formed a stable perforated layer not observed previously in monodisperse studies, and influenced the stability of the remaining phases. Although the perforated layer was experimentally observed under good solvent conditions and in the melt state, further confirmation of its presence in systems under good solvent conditions required mapping real polymers onto mesoscale models that reflected, for example, different polymer rigidity, and excluded volume effects or direct influence of the surface, just to mention a few parameters. Finally, in this work, we show that mesoscale modeling successfully describes polydisperse models, which opens the way for rapid exploring of complex systems such as polydisperse Y-shaped brushes in selective or bad solvents or under non-equilibrium conditions.

A 3-D simulation of red blood cells (RBCs) described as deformable cells in plasma flow is an indispensable element of blood flow analysis in the human vessels. To numerically investigate RBC motion in shear and Poiseuille flow, a mesoscale low dimensional-RBC method based on dissipative particle dynamics method has been successfully combined with a hybrid lattice Boltzmann method-immersed boundary method. This new model decreases the computational cost compared to the low dimensional RBC method and models the deformation of red blood cell accurately. To evaluate and validate the present numerical method, the relationship between the RBC diameter and the force value derived by the low dimensional-RBC method is compared with numerical and experimental data. In addition, as a benchmark test, the deformation index as the function of the capillary number of RBC motion through a narrow cylindrical tube has been performed. The behaviour of RBC in a shear flow and Poiseuille flow has been investigated. The present results demonstrated that this model is applied to reduce the computational cost, while maintaining the model precision. [ABSTRACT FROM AUTHOR]

The temporal and spatial evolution of shear banding during startup and steady-state shear flow was studied for solutions of entangled, linear, monodisperse polyethylene C 3000 H 6002 dissolved in hexadecane and benzene solvents. A high-fidelity coarse-grained dissipative particle dynamics method was developed and evaluated based on previous NEMD simulations of similar solutions. The polymeric contribution to shear stress exhibited a monotonically increasing flow curve with a broad stress plateau at intermediate shear rates. For startup shear flow, transient shear banding was observed at applied shear rates within the steady-state shear stress plateau. Shear bands were generated at strain values where the first normal stress difference exhibited a maximum, with lifetimes persisting for up to several hundred strain units. During the lifetime of the shear bands, an inhomogeneous concentration distribution was evident within the system, with higher polymer concentration in the slow bands at low effective shear rate; i.e., γ ˙ < τ R − 1 , and vice versa at high shear rate. At low values of applied shear rate, a reverse flow phenomenon was observed in the hexadecane solution, which resulted from elastic recoil of the molecules within the slow band. In all cases, the shear bands dissipated at high strains and the system attained steady-state behavior, with a uniform, linear velocity profile across the simulation cell and a homogeneous concentration. [ABSTRACT FROM AUTHOR]

Most of the existing hemolysis mechanism studies are carried out on the macro flow scale. They assume that the erythrocyte membranes with different loads will suffer the same damage, which obviously has limitations. Thus, exploring the hemolysis mechanism through the macroscopic flow field information is a tough challenge. In order to further understand the non-physiological shear hemolysis phenomenon at the cell scale, this study used the coarse-grained erythrocytes damage model at the mesoscopic scale based on the transport dissipative particle dynamics (tDPD) method. Combined with computational fluid dynamics the hemolysis of scalarized shear stress (1) in the clearance of "Impella 5.0" was evaluated under the Lagrange perspective and Euler perspective. The results from the Lagrange perspective showed that the change rate of scaled shear stress (...τ) was the most critical factor in damaging RBCs in the rotor region of "Impella 5.0 and other transvalvular micro-axial blood pumps. Then, we propose a dimensionless number Dk with time integration based on ...τ to evaluate hemolysis. The Dissipative particle dynamics simulation results are consistent with the Dk, evaluation results, so ...τ may be an important factor in the hemolysis of VADs. Finally, we tested the hemolysis of 30% hematocrit whole blood in the "Impella 5.0" shroud clearance from the Euler perspective. Relevant results indicate that because of the wall effect, the RBCs near the impeller side are more prone to damage, and most of the cytoplasm is also gathered at the rotor side. [ABSTRACT FROM AUTHOR]

We consider a functional surface comprising thermoresponsive polymer chains, the material that has found numerous technological and biomedical applications. However, to achieve the required time and length scales for computer modelling of such applications, one is compelled to use coarse-grained mesoscopic modelling approaches. The model used here is based on the previous work [Soto-Figueroa et al., Soft Matter, 8, 1871 (2012)], and it mimics the principal feature of the poly(N-iso-propylacrylamide) (PNIPAM), namely, the rapid change of its hydrophilicity at the lower critical solution temperature (LCST). For the case of an isolated chain, we discuss scaling properties of the radius of gyration, end-to-end distance, various distribution functions, and the density profile of monomers below and above the LCST. For the case of the model thermoresposive brush, we search for the optimum grafting density at which the change in the brush height, upon crossing the LCST, reaches its maximum value. The interpretation of the thermoresponse, in terms of the Alexander-de Gennes blobs and the level of solvation of polymer chains in a brush, is provided. [ABSTRACT FROM AUTHOR]

Given the importance of preserving the mechanical properties of recycled isotactic polypropylene (iPP) during its processing, this work provides an improved understanding of the contribution of introducing physical or chemical crosslinks using the dissipative particle dynamics (DPD) method, which makes it possible to model iPP structures with a realistic range of crosslink densities. First, the protocol to build a coarse‐grained model of iPP from an all‐atom expression by Bayesian optimization is described. A Bayesian optimization procedure employing two different cutoff distances successfully provides optimal DPD parameters reproducing iPP's properties compared to the all‐atom system. Then, the coarse‐grained iPP model with optimal DPD parameters is applied to study structures containing a realistic range of crosslink densities to evaluate their mechanical properties. These calculations demonstrate that the mechanical properties such as the Young's modulus and ultimate strength increase while the fracture strain decreases with an increase in the crosslink density, which is consistent with experimental observations. The results also show that there is a critical crosslink density above which these properties start to be improved due to the introduction of crosslinks. These findings can help us to obtain targeted properties of recycled iPP by introducing physical or chemical crosslinks. [ABSTRACT FROM AUTHOR]

In this study, an investigation has been carried out regarding the reciprocating translocation (i.e. back and forth motion) of a polymer chain in a microchannel. External force is one of the important factors in the movement of the polymer chain. In this investigation, variable forces are applied to the polymer chain and all fluid particles in which at a certain time, the direction of the force and the movement will change in this simulation. The behaviour and the properties of the chain, such as the radius of gyration, the centre of mass velocity and the amount of translocation, have been examined in this reciprocating movement. Based on the present results, when employing a longer polymer chain and especially applying the force on the polymer and fluid particles, due to the inertia effect, it would not be easily possible to stop the polymer chain. Consequently, changing the direction of polymer motion would not instantly occur by changing the force direction. In fact, some amount of displacement and lost time (LT) (around 6 dissipative particle dynamics units out of a total time of 40) will be associated with the case of applying force on just a polymer chain and imposing variable external force on all particles, LT has increased dramatically (dimensionless LT parameter is around 50%). The present method is a suitable tool for simulating the variable movement of polymer for the design of micro-actuators or polymer sensors. [ABSTRACT FROM AUTHOR]

Surfactin is a kind of special and efficient cyclic lipopeptide biosurfactant, which is composed of a seven‐peptide ring and a fatty acid tail chain and is widely used in the fields of medicine, environmental remediation and heavy oil transportation. This special ring structure also makes surfactin have great application potential in biomedicine and surface catalysis. In this work, the self‐assembly behavior of surfactin‐like polymer in selective solvents was studied by dissipative particle dynamics. By changing the interaction parameters, the size of the hydrophilic ring, the length of the hydrophobic tail chain and the concentration, a series of structures such as vesicles, disk‐like micelles, worm‐like micelles, sphere‐like micelles and ring‐like micelles were obtained from the establishment of the phase diagram. We explored the dynamic formation paths of vesicles and ring‐like micelles and discovered morphological changes during their aggregation. The mechanism of sphere‐like micelle formation at lower concentration was also studied, explained by the packing of molecules of effective conical shape. The structural properties of the vesicles were also intensively studied. Based on the special ring structure of surfactin‐like polymers, we explored the difference in their self‐assembly behavior from those of linear block copolymers and giant surfactant‐like polymers. A detailed study on the self‐assembly of surfactin‐like polymer can deepen the understanding of ordered aggregates of cyclic surfactants in selective solvents and can drive important implications for their practical application. © 2023 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

In this paper, the two-dimensional Kelvin–Helmholtz (KH) instability occurring in the shear flow of polymer fluids is modeled by the dissipative particle dynamics (DPD) method at the coarse-grained molecular level. A revised FENE model is proposed to properly describe the polymer chains. In this revised model, the elastic repulsion and tension are both considered between the adjacent beads, the bond length of which is set as one segment's equilibrium length. The entanglements between polymer chains are described with a bead repulsive potential. The characteristics of such a KH instability in polymer fluid shear flow can be successfully captured in the simulations by the use of the modified FENE model. The numerical results show that the waves and vortexes grow more slowly in the shear flow of the polymer fluids than in the Newtonian fluid case, these vortexes become flat, and the polymer impedes the mixing of fluids and inhibits the generation of turbulence. The effects of the polymer concentration, chain length, and extensibility are also investigated regarding the evolution of KH instability. It is shown that the mixing of two polymer fluids reduces, and the KH instability becomes more suppressed as the polymer concentration increases. The vortexes become much longer with the evolution of the elongated interface as the chain length turns longer. As the extensibility increases, the vortexes become more flattened. Moreover, the roll-up process is significantly suppressed if the polymer has sufficiently high extensibility. These observations show that the polymer and its properties significantly influence the formation and evolution of the coherent structures such as the waves and vortexes in the KH instability progress. [ABSTRACT FROM AUTHOR]

Abstract The influence of molecular fragmentation and parameter settings on a mesoscopic dissipative particle dynamics (DPD) simulation of lamellar bilayer formation for a C10E4/water mixture is studied. A “bottom-up” decomposition of C10E4 into the smallest fragment molecules (particles) that satisfy chemical intuition leads to convincing simulation results which agree with experimental findings for bilayer formation and thickness. For integration of the equations of motion Shardlow’s S1 scheme proves to be a favorable choice with best overall performance. Increasing the integration time steps above the common setting of 0.04 DPD units leads to increasingly unphysical temperature drifts, but also to increasingly rapid formation of bilayer superstructures without significantly distorted particle distributions up to an integration time step of 0.12. A scaling of the mutual particle–particle repulsions that guide the dynamics has negligible influence within a considerable range of values but exhibits apparent lower thresholds beyond which a simulation fails. Repulsion parameter scaling and molecular particle decomposition show a mutual dependence. For mapping of concentrations to molecule numbers in the simulation box particle volume scaling should be taken into account. A repulsion parameter morphing investigation suggests to not overstretch repulsion parameter accuracy considerations.

A self-healing epoxy material is considered, based on bisphenol A diglycidyl ether and atricarboxylic fatty acid hardener, belonging to a new class of polymers called vitrimers. The res toration of the integrity of such systems in the case of a damage occurs due to the exchange reaction of covalent bonds between the comonomers forming a polymer network. In our previous work, we have developed a model of this material based on the method of reactive dissipative particle dynamics. In this work, we apply our model to study the welding process of vitrimer samples cut into two parts. The control of the integrity of the structure of the systems was carried out using a topological analysis by calculating the distributions over the lengths of simple cycles and the density of the number of load-bearing circuits. It has been shown that the rate of restoration of the integrity of the systems is determined by the concentration of the catalyst and the degree of crosslinking of the polymer. The results obtained also indicate that in the case of a high degree of crosslinking of the polymer, as well as a low catalyst concentration, the structure of the system is highly inhomogeneous.

The transient elongational viscosity η e (t) of the polymer melt is known to exhibit strain hardening, which depends on the strain rate ε ˙ . This phenomenon was elucidated by the difference of chain stretching in the entanglement network between extension and shear. However, to date, the microscopic evolution of polymer melt has not been fully statistically analyzed. In this work, the radial size distributions P( R g , t ) of linear polymers are explored by dissipative particle dynamics during the stretching processes. In uniaxial extensional flow, it is observed that the mean radius of gyration R ¯ g (t) and standard deviation σ (t) remain unchanged until the onset of strain hardening, corresponding to linear viscoelasticity. Both R ¯ g and σ rise rapidly in the non-linear regime, and bimodal size distribution can emerge. Moreover, the onset of strain hardening is found to be insensitive to the Hencky strain ( ε ˙ H t ) and chain length (N). [ABSTRACT FROM AUTHOR]