Water-like Fluid Research Articles

Wormlike Micelles with Photo and pH Dual-Stimuli-Responsive Behaviors Formed by Aqueous Mixture of Cationic and Anionic Surfactants

Responsive wormlike micelles, innovative soft materials with stimuli-tunable rheological properties, have recently attracted significant attention. Herein, the construction of dual responsive wormlike micelles exhibiting photo- and pH-stimulated viscoelastic behaviors is demonstrated from a cationic surfactant 4,4′-bis(trimethylammonium-6-hexyloxy) azobenzene bromide (BTHA), and anionic surfactant sodium oleate (NaOA). Rheological measurement, dynamic light scattering, and cryogenic transmission electron microscopy were used to explore the dual-responsive behaviors of wormlike micelles system systematically. The results show that the self-assembly structures and viscoelastic behaviors of the mixed system can be regulated by light irradiation and pH. With BTHA concentration ≥ 20 mM, the mixed solutions show a shear-thinning behavior, implying the formation of wormlike micelles. Under UV light irradiation at 365 nm, the photoisomerization of BTHA from trans to cis affects the molecular packing at micellar interface, that leads to the aggregate structures transformation from wormlike micelles into spherical micelles, accompanied by an apparent decrease in zero-shear viscosity of the mixed solution by three orders of magnitude. The transformation is reversible in the presence of Vis light (420 nm). Moreover, the pH-responsive behavior could also be reversibly switched by adding HCl or NaOH, due to the protonation of NaOA molecules. The interconversion of gel-like solution and water-like fluid could occur by adjusting pH values between 10.26 and 8.95, which reflect variations in microstructures and was ascertained the transformation between wormlike micelles and spherical micelles by cryo-TEM. The relationship of temperature and the structural relaxation time (τR) follows the Arrhenius law, resulting from the decreasing micellar contour length. This work will enhance our understanding of the multi-responsiveness of intelligent materials and hold great promising applications in biomedicine, oil industry, smart molecular device, and sensors.

A novel prewetting behavior of water adsorbed on solid surfaces modified with tethered chains resulting from a density functional theory

The density functional approach for classical associating fluids is used to explore wetting phase diagrams for model systems consisting of water and graphite-like solid surfaces chemically modified by a small amount of grafted chain molecules. The water-like fluid model is adopted from the work of Clark et al. [Molec. Phys. 104, 3561 (2006)]. It describes the bulk water vapor–liquid coexistence very well. Each chain molecule consists of tangentially bonded hard spheres. We focus on the investigation of the growth of water film on such a complex substrate and the construction of the wetting phase diagram. We have found that the topology of the phase diagram depends on the amount of grafted chains and on the length of chains. At low grafting densities and for short chains, the prewetting phase diagrams are similar to the diagrams for water on a non-modified solid surface. For higher grafting densities and for longer chains, the prewetting line can split into two lines that join at a triple point. Each of the lines is associated with changes in the predominant configuration of segments of grafted chains. They can either stretch or coil upon the growth of an adsorbed film. Trends of the behavior of wetting temperature and the critical temperatures of the branches of the prewetting transition are discussed.

PH-responsive worm-based viscoelastic fluid formed by a dynamic covalent gemini surfactant

Responsive viscoelastic fluids based on wormlike micelles have attracted significant interest both in laboratory research and industrial applications due to their intelligent rheological response. However, pH-responsive worm-based viscoelastic fluids based on a dynamic imine surfactant remain a significant challenge. Herein, a novel worm-based viscoelastic fluid that can response to pH was fabricated utilizing a dynamic covalent gemini surfactant featuring a imine-type spacer. This unique gemini imine surfactant could be expediently obtained in situ by simply mixing an aldehyde-containing cationic surfactant (HOBAB) and hexyldiamine (C6DA) in water at a stoichiometric ratio of 2:1. Rheology and cryo-TEM experiments both demonstrated the formation of elongated wormlike micelles, responsible for the viscoelastic fluid. Because of its pH-sensitivity, the gemini imine surfactant could be damaged under acidic conditions and reformed under alkali conditions. Consequently, the solution of HOBAB and C6DA can be switched between a water-like fluid and worm-based viscoelastic fluid. Changing the precursors, such as the alkyldiamine or length of the hydrophobic chain, can also tailor the worm-based viscoelastic fluid based on a dynamic imine surfactant. For the C2-C6 spacer precursors, the viscoelastic fluid mainly resulted from the WLMs-based network, but for the C8 spacer precursor, it mainly originated from the densely packed of vesicles.

Experimental study of degradable preformed particle gel (DPPG) as temporary plugging agent for carbonate reservoir matrix acidizing to improve oil recovery

Preformed particle gel (PPG) is an effective technique for conformance improvement in petroleum reservoirs. It can selectively penetrate high-permeability channels to form effective plugging and divert the chasing injection fluid to low-permeability unswept oil zones. However, conventional PPG would be dehydrated under acidic conditions and could not be easily degraded, which will cause a certain amount of damage to the target formation. Therefore, this study proposed to introduce acid-resistant functional groups and a self-degradable cross-linking structure into the conventional PPG's compositions to develop a degradable PPG (DPPG). The influence mechanism of the chemical composition, swelling performance, and temporary plugging performance of DPPG was studied. Results show that the DPPG can swell up to 70 times its original size by absorbing water, and swollen DPPG can finally self-degrade to a water-like fluid in acid solution. After injecting of DPPG swelled by 20 times its original volume, the injection pressure could reach 1250 psi. Even during the chase acid treatment period, the average pressure was around 130 psi, which shows excellent plugging performance. Subsequent injection of acid would react with carbonate rocks around the plugging zones, increasing the swept volume. In addition, after acid treatments, the DPPG could be self-degraded into a dilute solution like water, so it has very little damage to the reservoir matrix. Therefore, the DPPG has good temporary plugging and acidizing steering performance in acidizing operations. The research in this article can provide the experimental basis and reference for expanding the further application of DPPG in petroleum reservoir stimulation. • Acid-resistant and self-degradable cross-linking structures were introduced to develop a degradable PPG. • The swelling and degradation performance can be adjusted by changing its component concentration. • Coreflooding test reveals that DPPG has a good acid diversion function. • DPPG can undergo self-degradation in a wide range of acidity.

Explaining the Nature of the Mass m of Submicroparticles and the Phenomenon of Mass Variation with Velocity V in Ether

A brief history of mass nature is presented, including formulas for mass variation with velocity V. A new mass hypothesis (MH), on the nature of mass m is presented. Accordingly, the mass m0 of submicroparticle (SMP), is given by the kinetic energy accumulated inside the SMP, by the vortices/vibrations of groups of ether (ETH) cells, constituting the submicroparticles (SSMP). These SSMPs will also create the inertial force (FI) of the SMP, due to the opposition manifested by ETH, toward any accelerated movement of SMP. A new explanation of mass m increase, with V is proposed, admitting the existence of ether in the form of our model, HM16. The entrainment of the surrounding ETH of SMP, takes place, with speed VETH, which stores the EETH energy. The spatial variation of VETH around the SMP, was analysed using the method of potential motions, for a cylinder, moving in water-like fluid, or in ETH, resulting a spectrum of the lines of current ψ, indicating the size of VETH, rapidly decreasing with distance r. So resulted the kinetic energy EETH stored by the movement of the outer ETH, which provides the supplementary mass ms. The case of SMP which acquires velocity V, approaching c, was analysed. Then, a phase change (PC) will take place, through which the SMP, transforms into photons (PHs), when movements of the ETH from the outside including energy EETH is transferred into PH photons, having velocity c, representing ETH’s property.

Competing interactions near the liquid-liquid phase transition of core-softened water/methanol mixtures

Water is a unique material with a long list of thermodynamic, dynamic and structural anomalies, which are usually attributed to the competition between two characteristic length scales in the intermolecular interaction. It has been argued that a potential liquid-liquid phase transition (LLPT) ending at a liquid-liquid critical point (LLCP) lies at the core of the anomalous behavior of water. This transition which has been evidenced in multiple simulation studies seems to be preempted experimentally by spontaneous crystallization. Here, in order to expose the connection between the spontaneous crystallization observed in the supercooled regime in the vicinity of the LLPT, and the density anomaly, we perform extensive Molecular Dynamics simulations of a model mixture of core-softened water and methanol. The pure water-like fluid exhibits a LLPT and a density anomaly. In contrast, our pure methanol-like model does have a LLPT but lacks the density anomaly. Our results illustrate the relation between the vanishing of the density anomaly and an increase in the temperature of the spontaneous crystallization: once this temperature surpasses the LLCP critical temperature, no density anomaly is observed. This peculiar feature illustrates how fine tuning the competitive interactions determine the anomalous behavior of water/alcohol mixtures.

A New Method of Gelatin Modified Collagen and Viscoelastic Study of Gelatin-Collagen Composite Hydrogel

Pure collagen materials are expensive with poor mechanical properties, which need modifications in most cases. As the degradation product of collagen, gelatin is cheap, degradable and biocompatible, but few literatures have reported the research about gelatin-collagen composite materials. This is because gelatin and collagen have different soluble temperatures—gelatin is soluble in hot water (≥30 °C) and swells in cold water. However, a low temperature (2–10 °C) is required to prepare and store collagen solution, and neutral collagen solution denatures quickly above the room temperature. In this study, gelatin was ground into powders and swelled in neutral bovine tendon pepsin-soluble collagen solution (BPSC) to form a homogeneous gelatin-collagen mixture, in light of the swelling characteristics of gelatin in cold water. The assembly properties and gel properties of this composite material were further studied. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) test results showed that the bovine tendon collagen had typical type-I collagen structural characterizations with two α chains of about 100 kDa and one β chain of about 200 kDa; while the SDS-PAGE pattern of gelatin displayed bands continuously distributed from 30 to 200 kDa. Amino acid composition analysis test indicated that the content of polar amino acids and the sum of acidic and base amino acids for gelatin were higher than that of BPSC. Studies on gel properties demonstrated that gelatin-collagen mixed solution had collagen-like assembly characteristics and assembly kinetics. The moduli of the assembled gel at 35 °C were equivalent to that of pure bovine tendon collagen system; moreover, the system moduli didn’t change with time with elastic moduli (G′) of about 40 Pa. However, at 25 °C, the moduli of gelatin-collagen composite hydrogel increased with the extension of time, its G′ increased about 18 times within 8 h, and the ratio of elastic modulus to viscous modulus (G″) increased 4.6 times, showing a significant aging effect of structural strength. Meanwhile, the mechanical strength of the composite hydrogel was also regulated by temperature—the gel was highly elastic (G′≈3,000 Pa, G′>>G″) at a low temperature (5 °C); as the temperature rose, the system moduli gradually decreased and the elastic gel transformed into waterlike fluid at 50 °C little by little. What’s more, gelatin-collagen composite hydrogel also had reversible sol-gel performances and self-healing capability similar to the gelatin hydrogel. This novel preparation method for preparing composite materials and the resultant composite hydrogel are expected to be used in the fields of natural food gels, injectable hydrogels, cell scaffolds, drug sustained-release materials and so on, and improve and promote the processing performances, price and large-scale production of collagen-based materials.

Towards the description of water adsorption in slit-like nanochannels with grafted molecular brushes. Density functional theory

We have explored a model for adsorption of water into slit-like nanochannels with two walls chemically modified by grafted polymer layers forming brushes. A version of density functional method is used as theoretical tools. The water-like fluid model adopted from the work of Clark et al. [Mol. Phys., 2006, 104, 3561] adequately reproduces the bulk vapour-liquid coexistence envelope. The polymer layer consists of chain molecules in the framework of pearl-necklace model. Each chain molecule is chemically bonded to the pore walls by a single terminating segment. Our principal focus is in the study of the dependence of polymer layer height on grafting density and in the microscopic structure of the interface between adsorbed fluid and brushes. Thermal response of these properties upon adsorption is investigated in detail. The results are of importance to understand shrinking and swelling of the molecular brushes in the nanochannels.

On the solvation force of water-like fluid models with square-well attraction and site–site association in slit-like pores: density functional approach

The solvation force of the water-like fluid models with square-well attraction and site–site chemical association confined to slit-like pores has been explored. Theoretical procedure is based on the application of the density functional approach with mean-field approximation for the attractive interparticle interactions. The chemical association effects are treated by using the first-order thermodynamic perturbation theory of Wertheim. Trends of behaviour of the solvation force are put in correspondence with the distribution of molecules in the pores and with the average density of the adsorbate. Moreover, the distribution of non-bonded species on pore width is described. The influence of the width of the square-well and of the gas–solid attraction is discussed. A comparison of theoretical predictions with computer simulations results for water models in slit-like pores is performed.

Responsive wormlike micelle with pH-induced transition of hydrotrope based on dynamic covalent bond

Dynamic covalent bonds are widely used to construct nanosystems or self-healing materials with stimulus response. Here we developed a responsive wormlike micelles system based on pH-directed hydrophilic of hydrotrope, which was formed by mixing the cetyltrimethylammonium bromide (CTAB), 4-formylbenzoic acid (FA) and hexylamine (HA) at the molar ratio of 60:25:25 (CTAB/FA/HA). The rheological measurement, appearance observation, Cryo-TEM and 1H NMR were used to explore the characteristics of solution. With the pH increase from 6.01 to 12.07, the CTAB/FA/HA solution underwent transitions from a water-like fluid to viscoelastic fluid and finally converted to a gel-like solution, and the viscosity continuously increased from ~1.1 mPa·s to ~68,000 mPa·s. The drastic variation in rheological behaviour was attributed to the pH dependent combination of FA− and HA, which reduced the hydrophilicity of FA− and made hydrotrope transfer from the aqueous phase to the interior of the micelle. In contrast, the CTAB/p-phthalic acid/HA solution cannot achieve transition of hydrotrope due to the consistent hydrophilicity of disodium phthalate (p-DPA2−) and the viscoelasticity without any change by increasing pH. Besides, the viscoelasticity of CTAB/FA/HA solutions can be reversed over 3 cycles by adjusting the pH.

Endowing conventional hydrophobic associating polymer solution CO2 stimuli-responsive property with a CO2 switchable surfactant

The performance of hydrophobic associating polymers could be significantly affected by addition of a small amount of surfactant, especially around the critical association concentration. In this work, a CO2 stimuli responsive surfactant, N, N-dimethyl oleoaminde-propylamine (PKO), was introduced into the hydrophobic associating polymer solution (PMA), which endowed the conventional hydrophobic associating polymer solution with CO2 stimuli responsive performance. The conductivity measurements indicated the molecular structure and properties of PKO could be regulated with bubbling and removal of CO2 and the protonated surfactant exhibited superior surface activity. In the presence of CO2, PKO interacted with hydrophobic monomer to be mixed micelles, which prompted the transition of PMA aggregation from intramolecular association to intermolecular association, exhibiting a gel-like fluid. With removal of CO2, the mixed micelles were dissociated and the viscosity of the solution decreased significantly, leading a water-like fluid. The reversible transition of aggregation and performance could be regulated reversibly through the presence and removal of CO2. The PMA-PKO systems with CO2 switchable performance would have wide applications in hydraulic fracturing and oil production.

Study of a Novel Gemini Viscoelastic Surfactant with High Performance in Clean Fracturing Fluid Application.

Gemini surfactant, as a functionally flexible polymer-like material in the aqueous solution, has attracted increased attention in reservoir stimulation of hydraulic fracturing in recent decades. A new Gemini cationic viscoelastic surfactant named JS-N-JS, which has a secondary amine spacer group and two ultra-long hydrophobic tails, was synthesized from erucamidopropyl dimethylamine, diethanolamine, and thionyl chloride as a thickener for hydraulic fracturing fluid. Compared with some Gemini cationic surfactant with methylene spacer, JS-N-JS showed a lower critical micellar concentration (CMC) and higher surface activity due to the hydrogen bond formed between the secondary amine and water molecule intends to reduce electrostatic repulsion, which is more beneficial to be the fracturing fluid thickener. Moreover, the performance of JS-N-JS solution can be further improved by salts of potassium chloride (KCl) or sodium salicylate (NaSal), while organic salt behaved better according to the measurements. The SEM observation confirmed that JS-N-JS/NaSal system owned a tighter network microstructure, and JS-N-JS/NaSal system exhibited a distinct superior viscoelasticity system at a sweep frequency of 0.1–10 Hz. As a fracturing fluid, the solution with a formula of 30 mmol JS-N-JS and 100 mmol NaSal was evaluated according to the petroleum industrial standard and presented excellent viscoelastic properties, the viscosity of which can maintain above 70 mPa·s for 110 min under a shear rate of 170 s−1 at 120 °C. Meanwhile, the drag reducing rate of the formula could reach above 70% with the increase of shear rate. Finally, the viscous fracturing fluid can be broken into the water-like fluid in 1.2 h after being fully exposed to hydrocarbons and the water-like fluid presented a low damage to the tight sand reservoirs according to the core flooding experiments, in which the permeability recovery rate can reach 85.05%. These results fully demonstrate that the JS-N-JS solution fully meets the requirement of the industrial application of hydraulic fracturing.

Adsorption and phase behavior of water-like fluid models with square-well attraction and site-site association in slit-like pores: Density functional approach.

The adsorption and phase behavior of two model fluids, both with square well inter-particle attraction and site-site associative interaction, in slit-like pores have been studied in the framework of a density functional theory. The mean field approach and the first-order mean spherical approximation have been applied to account for the attractive interactions. The chemical association effects are taken into account by using the first-order thermodynamic perturbation theory of Wertheim. A set of parameters for each fluid model has been chosen according to the work of [Clark et al., Mol. Phys. 104, 3561 (2006)], to describe successfully the vapor-liquid coexistence of water in the bulk phase. The influence of the slit-like pore width and of the strength of gas-solid interaction energy on the vapor-liquid coexistence envelope under confinement has been explored in detail. The theory and the results of the present work are valuable for further exploration of a wide set of models of associating fluids and of fluids with complex molecular architecture in different adsorbents, and to deal with activated carbon surfaces.

Self-assembly of the butterfly proboscis: the role of capillary forces.

The proboscis of butterflies and moths consists of two C-shaped fibres, the galeae, which are united after the insect emerges from the pupa. We observed that proboscis self-assembly is facilitated by discharge of saliva. In contrast with vertebrate saliva, butterfly saliva is not slimy and is an almost inviscid, water-like fluid. Butterfly saliva, therefore, cannot offer any viscoelastic adhesiveness. We hypothesized that capillary forces are responsible for helping butterflies and moths pull and hold their galeae together while uniting them mechanically. Theoretical analysis supported by X-ray micro-computed tomography on columnar liquid bridges suggests that both concave and convex liquid bridges are able to pull the galeae together. Theoretical and experimental analyses of capillary forces acting on natural and artificial proboscises show that these forces are sufficiently high to hold the galeae together.

Relation between boundary slip mechanisms and waterlike fluid behavior.

The slip of a fluid layer in contact with a solid confining surface is investigated for different temperatures and densities using molecular dynamic simulations. We show that for an anomalous waterlike fluid the slip goes as follows: for low levels of shear, defect slip appears and is related to the particle exchange between the fluid layers; at high levels of shear, global slip occurs and is related to the homogeneous distribution of the fluid in the confining surfaces. The oscillations in the transition velocity from defect to global slip are shown to be associated with changes in the layering distribution in the anomalous fluid.

A new high accuracy meshfree method to directly simulate fluid dynamics and heat transfer of weakly compressible fluids

A Tayler series expansion based high accuracy meshfree method (TS-HAMM) is developed to calculate first and second derivatives of property values stored in dispersed particle clouds. Compared with other meshfree methods such as smoothed particle hydrodynamics (SPH), TS-HAMM can (a) systematically increase accuracies in gradient, derivative and Laplacian calculations with similar computational cost; (b) provide boundary conditions directly from conservation equations at the fluid/solid interfaces with guaranteed order of accuracy; (c) simulate fluid dynamics and heat transfer of low viscous weakly compressible fluid (e.g. water) directly without making incompressible assumptions. Through numerical verifications with water-like low viscous low compressible fluid in Couette flow, lid-driven flow inside a cavity, and natural convection inside an enclosure, we justify the validity of TS-HAMM in simulating fluid dynamics and heat transfer of water-like low viscous weakly compressible fluid, which are challenging with other meshfree methods such as smoothed particle hydrodynamics (SPH).

A responsive anionic wormlike micelle using pH-directed release of stored sodium based on polybasic acids.

Responsive wormlike micelles are very useful in a number of applications, whereas it is still challenging to create dramatic viscosity changes in anionic surfactant systems. Here a differential pH-responsive wormlike micelle based on sulfonic surfactants was developed, which is formed by mixing sodium dodecyl trioxyethylene sulphate (SDES) and ethylenediaminetetraacetic acid tetrasodium (EDTA4-·4Na+) at the molar ratio of 1 : 1. The phase behavior, aggregate microstructure and viscoelasticity of the SDES/EDTA4-·4Na+ solution were investigated via macroscopic observation, cryo-TEM and rheological measurements. It was found that the phase behavior of the SDES/EDTA4-·4Na+ solution undergoes transitions from a water-like fluid to viscoelastic upon decreasing the pH. On decreasing the pH from 12.01 to 3.27 by adding HCl, the viscosity of the transparent solutions with wormlike micelles was increased rapidly and reached ∼3100 mPa s. Furthermore, on increasing the pH by adding NaOH, the viscosity was slightly increased due to the addition of Na+. However, the increase in the concentration of Na+ is much smaller than the theoretical addition. The same phenomenon was noted in the sodium citrate solution, but does not exist in the sodium formate system. The viscosity of the micellar solution has a sensitive response to inorganic acids and tolerance to inorganic bases due to the characteristics of polybasic acids.

Tackling the life and death of whirls

Fluid Mechanics Energy in a turbulent system moves from large eddies to smaller ones until it is dissipated by viscous motion. The details of exactly how this works have remained obscure, in part because of the challenge of simulating fluids across many length scales in three dimensions over time. Cardesa et al. present a large numeric simulation of a water-like fluid that shows characteristic length scales for the birth and death of turbulent whirls. The approach can be extended to understand energy transfer in the atmosphere, plasmas, and other complex systems. Science , this issue p. [782][1] [1]: /lookup/doi/10.1126/science.aan7933

The turbulent cascade in five dimensions.

To the naked eye, turbulent flows exhibit whirls of many different sizes. To each size, or scale, corresponds a fraction of the total energy resulting from a cascade in five dimensions: scale, time, and three-dimensional space. Understanding this process is critical to strategies for modeling geophysical and industrial flows. By tracking the flow regions containing energy in different scales, we have detected the statistical predominance of a cross-scale link whereby fluid lumps of energy at scale Δ appear within lumps of scale 2Δ and die within those of scale Δ/2. Our approach uncovers the energy cascade in a simple water-like fluid, offering insights for turbulence models while paving the way for similar analyses in conducting fluids, quantum fluids, and plasmas.

Single-file mobility of water-like fluid in a generalized Frenkel-Kontorova model.

In this work, we used a generalized Frenkel-Kontorova model to study the mobility of water molecules inside carbon nanotubes with small radius at low temperatures. Our simulations show that the mobility of confined water decreases monotonically increasing the amplitude of the substrate potential at fixed commensurations. On the other hand, the mobility of the water molecules shows a non-monotonic behavior when varying the commensuration. This result indicates that the mobility of the confined fluid presents different behavior regimes depending on the amplitude of the water-nanotube interaction. In order to qualitatively understand these results, we study analytically the driven Frenkel-Kontorova model at finite temperatures. This analysis allows us to obtain the curves of the mobility versus commensurations, at fixed substrate potentials. Such curves show the existence of three regimes of mobility behavior as a function of the commensuration ratio. Additionally, our study indicates a nontrivial and strong dependence of the mobility with a quantity that can be interpreted as an effective amplitude of the substrate potential, depending on the bare amplitude of the substrate potential, the commensuration ratio, and temperature.