Large-scale spatial arrangement and orientation ordering of nanorod assembly on substrates are critical for nanodevice fabrication. However, complicated processes and templates or surface ...modification of nanorods are often required. In this work, we demonstrate, by dissipative particle dynamics simulations, that various ordered structures of adsorbed nanorods on smooth substrates can be simply achieved by non-affinity adsorption. The structures of interfacial assembly, including monolayers with a nematic-like arrangement and multilayer stacking with a smectic-like arrangement, depend on the nanorod concentration and the solvent size. As the nanorod concentration increases, the adsorbed layer becomes densely packed and the arrangement of nanorods changes from nematic-like to smectic. The assembly process driven by entropy is a two-dimensional layer-by-layer growth. Multilayer stacking with a smectic-like arrangement takes place at dilute concentrations of nanorods for large solvents such as pentamers, but at concentrated concentrations, it takes place for small solvents such as monomers. Moreover, nanorod bundles appear in the bulk phase for large solvents at dilute concentrations. The proposed strategy for interfacial assembly is caused by the free volume released for solvents, which is independent of the chemical compositions of substrates and nanorods.
The structures of adsorbed nanorods on smooth substrates, including monolayer with nematic-like arrangement and multilayer stacking with smectic-like arrangement, can be simply achieved by non-affinity adsorption.
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•Concentrated emulsions with solid-like behavior are simulated without prior knowledge of the interdroplet interaction.•Volume fraction (ϕ), droplet diameter (D), and interfacial ...tension (σ) affect Young’s modulus (E) and bulk modulus (K).•The mechanical properties are found to be droplet size-dependent, and they satisfy the relation E = 3 K(1 − 2ν).•Simulation results can be well represented by E(ϕ) ∼ ϕ0.13(ϕ − ϕc)1.55(σ/D) and K(ϕ) ∼ ϕ1.06(ϕ − ϕc) 0.15 (σ/D).•The scaling (σ/D) can be realized by the conversion of the work into the interfacial energy per unit volume.
Concentrated emulsions with volume fractions exceeding the critical value have diverse applications in foods, cosmetics, coatings, and pharmaceuticals. They have a jammed structure and tend to exhibit a solid-like behavior. Unfortunately, the mechanical properties of monodisperse concentrated emulsions are challenging to study by experiments or simulations because of thermodynamic instability and droplet coalescence. A mesoscopic simulation method is employed to study the mechanical properties of the concentrated emulsion. Knowledge of the microstructure and interdroplet interaction among monodisperse droplets is not a prerequisite. Effects of the volume fraction (ϕ), droplet diameter (D), and interfacial tension (σ) on Young’s modulus (E) and bulk modulus (K) are investigated systematically. For ϕ < ϕc, Young’s modulus is absent and the bulk modulus rises with increase ϕ. For ϕ > ϕc, both Young’s and bulk moduli are found to grow with increasing ϕ and σ. However, these solid-like properties become more prominent as D is decreased. On the basis of the interfacial energy per unit volume, our simulation results can be well represented by the relations E ∼ ϕ0.13(ϕ-ϕc)1.55(σ/D) and K ∼ ϕ1.06(ϕ-ϕc)0.15(σ/D). Moreover, the relationship for soft materials E = 3 K(1 − 2ν) is satisfied. The Poisson’s ratio (ν) is very close to 0.5 but still decreases slightly with increasing ϕ.
Graft copolymers with diblock side-chains A m (- graft -B 3 A y ) n in a selective solvent have been reported to self-assemble into vesicles, but the structure is expected to differ distinctly from ...those of lipid bilayers. Surprisingly, the number of alternating hydrophobic A-block and hydrophilic B-block layers in the vesicle can vary from a monolayer to multilayers such as the hepta-layer, subject to the same copolymer concentration. The area density of the copolymer layer is not uniform across the membrane. This structural difference among different layers is attributed to the neighboring environment and the curvature of the layer. Because of the unusual polymer conformations, nonlamellar structures of polymersomes are formed, and they are much more intricate than those of liposomes. In fact, a copolymer can contribute to a single or two hydrophilic layers, and it can provide up to three hydrophobic layers. The influence of the backbone length ( m ) and side-chain length ( y ) and the permeation dynamics are also studied. The thickness of hydrophobic layers is found to increase with increasing side-chain length but is not sensitive to the backbone length. Although the permeation time increases with the layer number for planar membranes, the opposite behavior is observed for spherical vesicles owing to the curvature-enhanced permeability associated with Laplace pressure.
Heavy metal ions are toxic to humans, plants, and marine life, making it crucial to eliminate them from water. This study reports the development of a new nanocomposite material (Alg@Ag/PU) that ...involves modifying silver nanoparticles (Ag NPs) with alginate (Alg) and coating them onto a polyurethane sponge (PU) for removing heavy metal ions. The successful coating of Alg@Ag NPs onto PU due to their strong chemical binding was confirmed by morphology and size characterization. Batch experiments were conducted to evaluate the removal efficiency of heavy metal ions at high concentrations (∼100 mg/L). The maximum adsorption amount was achieved within 6 h, and the highest removal efficiency was obtained at pH values between 6 and 7. Furthermore, the Alg@Ag/PU nanocomposite demonstrated excellent recyclability for metal ion removal even after 5 cycles. In summary, this work developed a simple and cost-effective method for producing an environmentally-friendly nanocomposite material for the efficient removal of heavy metal ions.
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•A new nanocomposite (Alg@Ag/PU) is developed for heavy metal ions removal.•Alg@Ag/PU is environmentally-friendly, cost-effective, reusable, and sustainable.•The removal efficiency of heavy metal ions remains great at high concentrations.•The composite has great recyclability, with high efficiency even after 5 cycles.
A ring-shaped stain is frequently left on a substrate by a drying drop containing colloids as a result of contact line pinning and outward flow. In this work, however, different patterns are observed ...for drying drops containing small solutes or polymers on various hydrophilic substrates. Depending on the surface activity of solutes and the contact angle hysteresis (CAH) of substrates, the pattern of the evaporation stain varies, including a concentrated stain, a ringlike deposit, and a combined structure. For small surface-inactive solutes, the concentrated stain is formed on substrates with weak CAH, for example, copper sulfate solution on silica glass. On the contrary, a ringlike deposit is developed on substrates with strong CAH, for example, a copper sulfate solution on graphite. For surface-active solutes, however, the wetting property can be significantly altered and the ringlike stain is always visible, for example, Brij-35 solution on polycarbonate. For a mixture of surface-active and surface-inactive solutes, a combined pattern of a ringlike and concentrated stain can appear. For various polymer solutions on polycarbonate, similar results are observed. Concentrated stains are formed for weak CAH such as sodium polysulfonate, and ring-shaped patterns are developed for strong CAH such as poly(vinyl pyrrolidone). The stain pattern is actually determined by the competition between the time scales associated with contact line retreat and solute precipitation. The suppression of the coffee-ring effect can thus be acquired by the control of CAH.
The wetting behavior of simple binary mixtures containing both partial and total wetting liquids is investigated on the commonly used substrates. The variation of the contact angle (CA) of the binary ...liquid with the composition (xP) on different solid surfaces is obtained. It is interesting to find that for the droplet which can exhibit self-propulsion, four different regimes can be identified in the CA-xP plot. Among them, the plateau regime where the CA remains a constant value in a certain concentration range is most intriguing. In contrast, for the droplet which cannot self-propel, the CA grows monotonously with the concentration of the partial wetting liquid. The leak-out phenomenon in which the droplet is surrounded by the precursor film is believed to occur in the plateau regime, and it is examined by observing the encounter of two miscible droplets by optical microscopy. The apparently noncontact repulsion between the moving and static droplets reveals the presence of the precursor film leaked out from the self-propelled droplet.
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Additive manufacturing is a promising technique for offering novel functionality to various materials by creating three-dimensional (3D) structures. However, the development of sustainable synthesis ...processes for 3D printing inks or 3D-printed materials remains a major challenge. In this work, a simple two-step mixing approach is developed to prepare a 3D printing ink from green, low-cost, and low-toxicity materials commercial Carbopol and deep eutectic solvents (DESs). A small weight fraction of Carbopol can impart desired rheological properties to the DES used in the 3D printing ink and also can significantly enhance the stretchability of eutectogels up to 2500% strain. The 3D-printed auxetic structure shows a negative Poisson’s ratio (within 100% strain), high stretchability (300%), high sensitivity (gauge factor of 3.1), good moisture resistance, and sufficient transparency. It can detect human motion with high skin comfort and breathability. The results of this work highlight a green, low-cost, and energy-saving strategy to fabricate conductive microgel-based inks for 3D printing of wearable devices.
Restrained molecular dynamics simulations were performed to study the interaction forces of a protein with the self-assembled monolayers (SAMs) of S(CH
2)
4(EG)
4OH, S(CH
2)
11OH, and S(CH
2)
11CH
3 ...in the presence of water molecules. The force-distance curves were calculated by fixing the center of mass of the protein at several separation distances from the SAM surface. Simulation results show that the relative strength of repulsive force acting on the protein is in the decreasing order of OEG-SAMs
>
OH-SAMs
>
CH
3-SAMs. The force contributions from SAMs and water molecules, the structural and dynamic behavior of hydration water, and the flexibility and conformation state of SAMs were also examined to study how water structure at the interface and SAM flexibility affect the forces exerted on the protein. Results show that a tightly bound water layer adjacent to the OEG-SAMs is mainly responsible for the large repulsive hydration force.
Droplets of a polymer solution can solidify in a nonsolvent bath, forming solid capsules and particles. However, the dynamics of this process, based on nonsolvent-induced phase separation, remains ...elusive. In this work, the solidification dynamics of polymer solution droplets is explored using dissipative particle dynamics simulations for different initial polymer concentrations. The dynamics of the shrinking droplets is monitored. Additionally, the evolutions of solvent and nonsolvent concentrations are examined, and the local polymer concentration profiles are analyzed. Furthermore, the microstructural characteristics of polymers, including the degree of crystallinity (local alignment) and the radius of gyration of polymers, are investigated. It is interesting to observe that the macroscopic morphology and microscopic configuration are significantly dependent on initial polymer concentrations. At higher concentrations, hollow particles are formed, containing polymer shells with longer persistence lengths. Conversely, lower concentrations lead to the creation of solid particles with increased chain-folding. Our results provide valuable insights into the influence of initial polymer concentrations on polymeric capsules and particle formation.
Nonsolvent-induced phase separation is widely used to create polymer membranes, but its demixing process is generally understood by liquid-liquid separation. In this work, the solidification dynamics ...of polymer solutions for membrane formation are explored through dissipative particle dynamics simulations. The shrinkage of the symmetric film of polymer solution is monitored, and the evolutions of the concentration profiles of polymer, solvent, and nonsolvent are analyzed. Additionally, the evolution of the degree of crystallinity (local alignment) and the morphology of the developing membrane are also studied. Three regions can be identified: (i) interfacial region, (ii) dense layer, and (iii) middle region. The demixing process associated with liquid-solid separation is found to be caused by the extraction of solvent and concentration of polymers rather than nonsolvent-induced separation. Our results provide valuable insights into directional solidification and spontaneous stratification of the membrane, driven by solvent loss and oversaturation (beyond the maximum solubility of polymer).
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•Solidification dynamics of polymer solutions for membrane formation is presented.•The shrinkage process involves negligible solvent-nonsolvent exchange.•Polymer precipitation is mainly driven by solvent loss and polymer oversaturation.•Spontaneous stratification emerges within the symmetric yet nonuniform membrane.
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