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Electrothermal pumping is a recently trending method to force highly conductive fluids in a wide range of microfluidics applications with biological processes. Although most polymer fluids (biological and synthetic) are highly conductive exhibiting viscoelastic rheological properties that are relevant to biomedical applications, their behavior under the effect of electrothermal force has not yet been studied. To this aim, the PTT model (non-linear rheological constitutive equation) and electrothermal equations are implemented in the developed OpenFOAM solver. The effect of rheological characteristics of the fluids on the physical parameters such as velocity, elastic behavior, and vortices strength of electrothermal flow are investigated through the viscoelastic non-dimensional numbers. According to the results, electrothermal outlet velocity decreases by 726% as the retardation ratio (β number) increases from 0.2 to 0.9 and increases by 107% as the Weissenberg number raises from 0.001 to 10. Investigating all non-dimensional numbers simultaneously leads to the conclusion that higher electrothermal velocity is achieved by viscoelastic fluids with lower viscosity and higher relaxation time. This fact is useful for choosing the proper fluid for a particular application. As a practical example, 3000 ppm polyethylene oxide solution results in higher velocity in electrothermal flow compared to the 5% polyvinylpyrrolidone and 2000 ppm xanthan gum solution.

The article examines the mechanism responsible for cluster formation in polymer solutions, a phenomenon observed in both high- and low-molecular solutions. In a two-component “solvent-solute” system, four phases can exist: pure solvent, pure solute, and two phases for the solution (sol phase and mesophase) In the sol phase, the particles (or molecules) of the solute are separated from each other, while in the mesophase, these particles (molecules) combine to form a framework. The chain serves as the structural unit of this framework. In high molecular weight solutions, the structural units are polymer chains. In low molecular weight solutions, a chain represents a linear sequence of solute particles connected to each other. A phase diagram is proposed for high molecular weight solutions, wherein the gel acts as a mesophase. The mesophase is an intermediate phase between the sol phase and the pure solute phase. In a specific range of concentrations and temperatures, the sol phase and mesophase coexist, resulting in a sol-phase matrix containing clusters of the mesophase. It is generally accepted that the aforementioned phase diagram is also applicable to low molecular weight solutions. Accordingly, the formation of clusters in solutions, known as clustering, is regarded as a first-order phase transition accompanied by the emergence of a mesophase. The existence of this transition was experimentally verified through light scattering by an aqueous solution of hydroxypropyl methylcellulose. A model of an ideal mesophase is proposed, characterized by the presence of two types of thermal oscillations in its framework. These are small-scale bending oscillations of chains and large-scale oscillations that propagate in the form of transverse waves. Based on the principles of statistical physics and elasticity theory, a formula for the free vibrational energy $f$ is derived for the proposed model. Numerical evaluation of $f$ leads to the conclusion that clustering (the formation of clusters in both high and low molecular weight solutions) is a first-order phase transition, i.e., a transition from the sol phase to the mesophase. This type of phase transition falls into the category of weak first-order phase transitions. [ABSTRACT FROM AUTHOR]

Electrothermal pumping is a recently trending method to force highly conductive fluids in a wide range of microfluidics applications with biological processes. Although most polymer fluids (biological and synthetic) are highly conductive exhibiting viscoelastic rheological properties that are relevant to biomedical applications, their behavior under the effect of electrothermal force has not yet been studied. To this aim, the PTT model (non-linear rheological constitutive equation) and electrothermal equations are implemented in the developed OpenFOAM solver. The effect of rheological characteristics of the fluids on the physical parameters such as velocity, elastic behavior, and vortices strength of electrothermal flow are investigated through the viscoelastic non-dimensional numbers. According to the results, electrothermal outlet velocity decreases by 726% as the retardation ratio (β number) increases from 0.2 to 0.9 and increases by 107% as the Weissenberg number raises from 0.001 to 10. Investigating all non-dimensional numbers simultaneously leads to the conclusion that higher electrothermal velocity is achieved by viscoelastic fluids with lower viscosity and higher relaxation time. This fact is useful for choosing the proper fluid for a particular application. As a practical example, 3000 ppm polyethylene oxide solution results in higher velocity in electrothermal flow compared to the 5% polyvinylpyrrolidone and 2000 ppm xanthan gum solution. [ABSTRACT FROM AUTHOR]

The polymer solution flow in porous media is a central research topic related to hydraulic fracturing measures, formation damage and fracture propagation. Influenced by molecular weights and concentrations, various flow patterns of polymer in pores are presented, resulting in different filtration loss. In this work, the effectiveness of various polymer solutions for filtration loss was assessed by utilizing the core flooding experiment firstly. The result shows that lesser filtration loss normally is inextricably linked to solutions with high molecular weight and concentration. Subsequently, the flow behaviors of polymer solutions investigated by designed micro pore-throat structure and micro-particle image velocimetry (μ-PIV) further confirmed the above result. It was found that the central convergent flow pattern benefiting from higher viscous force loss and less filtration loss was observed at high flow rates (0.5 mL/h), and higher molecular weight and concentration were more prone to convergent flow patterns. The viscosity force loss increases by about 4 times varying the molecular weight of polymer from 5 × 106 to 18 × 106 g/mol or the concentration from 0.05 to 0.3%. It interprets higher molecular weight and concentration in core studies and field observations with decreased filtration loss of HPAM. This work provides a theoretical foundation for the application of fracturing fluids as well as fresh perspectives on how to access the filtration loss of fracturing fluids.

The discrete control method of the mechanical properties and structure during heat treatment of grade 50 steel vessels with residual heating after thermomechanical treatment on the rolling-press line of the Bogorodsk branch of NPO Pribor is developed and studied. The advantages and disadvantages of cooling media are considered depending on the conditions of heat absorption. The influence of various compositions and concentrations of polymer aqueous solutions and mineral oil on the properties and structure of deformed vessels under cooling are studied. The possibility of varying the cooling media to regulate the cooling rate and properties of rolled products is shown. Analysis of the obtained research results makes it possible to establish collective patterns between the cooling rate, the resulting microstructure and the mechanical properties of grade 50 steel vessels at the outlet of the rolling-press line of the Bogorodsk branch of NPO Pribor. [ABSTRACT FROM AUTHOR]

Part I of this paper [Haward et al., J. Rheol. 67, 995–1009 (2023)] presents a three-dimensional microfluidic device (the optimized uniaxial and biaxial extensional rheometer, OUBER) for generating near-homogeneous uniaxial and biaxial elongational flows. Here, in Part II, the OUBER device is employed to examine the uniaxial and biaxial extensional rheology of model dilute polymer solutions, compared with measurements made under planar extension in the optimized-shape cross-slot extensional rheometer [OSCER, Haward et al. Phys. Rev. Lett. 109, 128301 (2012)]. In each case, micro-particle image velocimetry is used to measure the extension rate as a function of the imposed flow conditions, and excess pressure drop measurements enable estimation of the tensile stress difference generated in the fluid via a new analysis based on the macroscopic power balance for flow through each device. Based on this analysis, for the most dilute polymer sample tested, which is "ultradilute", the extensional viscosity is well described by Peterlin's finitely extensible nonlinear elastic dumbbell model. In this limit, the biaxial extensional viscosity at high Weissenberg numbers (Wi) is half that of the uniaxial and planar extensional viscosities. At higher polymer concentrations, although the fluids remain dilute, the experimental measurements deviate from the model predictions, which is attributed to the onset of intermolecular interactions as the polymer chains unravel in the extensional flows. Of practical significance (and fundamental interest), elastic instability occurs at a significantly lower Wi in uniaxial extensional flow than in either biaxial or planar extensional flow, thereby limiting the utility of this flow type for extensional viscosity measurement. [ABSTRACT FROM AUTHOR]

The vapor–liquid equilibrium of the fluorobenzene–polystyrene binary polymer solution at 303.15 K was measured using a static pressure device. The vapor–liquid equilibrium of the fluorobenzene–n-octane–polystyrene ternary solution in a partial concentration range under normal pressure was determined using an improved Othmer equilibrium still, in which the octane concentration was low. Three activity coefficient models, poly-NRTL, UNIQUAC, and M-UNIQUAC-LBY, were utilized to correlate the experimental data of binary and ternary solutions, and the component activities of the fluorobenzene–n-octane–polystyrene solution at 303.15 K were predicted. A mathematical model based on the Stefan flow was developed to simulate the evaporation process of composite spherical droplets. The activity predicted by the activity coefficient model was used for numerical simulations, and compared with simulations using the activity following Raoult's law. The comparative analysis revealed that simulations based on Raoult's law and activity coefficient models yielded similar results when the mass fraction of fluorobenzene exceeded 0.6. However, in the later stages of evaporation, the calculations based on Raoult's law predicted a 10% shorter drying time for fluorobenzene. The activity coefficient models provided a better approximation and exhibited similar droplet diameter shrinking behaviors to the actual evaporation process. [ABSTRACT FROM AUTHOR]

Polymeric materials are ubiquitous in our everyday life, where they find a broad range of uses—spanning across common household items to advanced materials for modern technologies. In the context of the latter, so called "smart polymers" have received a lot of attention. These systems are soluble in water below their lower critical solution temperature T ℓ and often exhibit counterintuitive solvation behavior in mixed solvents. A polymer is known as smart-responsive when a slight change in external stimuli can significantly change its structure, functionm and stability. The interplay of different interactions, especially hydrogen bonds, can also be used for the design of lightweight high-performance organic solids with tunable properties. Here, a general scheme for establishing a structure–property relationship is a challenge using the conventional simulation techniques and also in standard experiments. From the theoretical side, a broad range of all-atom, multiscale, generic, and analytical techniques have been developed linking monomer level interaction details with macroscopic material properties. In this review, we briefly summarize the recent developments in the field of smart polymers, together with complementary experiments. For this purpose, we will specifically discuss the following: (1) the solution processing of responsive polymers and (2) their use in organic solids, with a goal to provide a microscopic understanding that may be used as a guiding tool for future experiments and/or simulations regarding designing advanced functional materials. [ABSTRACT FROM AUTHOR]

In flows with re-entrant corners, polymeric fluids can exhibit a recirculation region along the wall upstream from the corner. In general, the formation of these vortices is controlled by both the extensional and shear rheology of the material. More importantly, these regions can only form for sufficiently elastic fluids and are often called "lip vortices". These elastic lip vortices have been observed in the flows of complex fluids in geometries with sharp bends. In this work, we characterize the roles played by elasticity and shear thinning in the formation of the lip vortices. Simulations of the Newtonian, Bird-Carreau, and Oldroyd-B models reveal that elasticity is a necessary element. A systematic study of the White-Metzner, finitely extensible non-linear elastic (FENE-P), Giesekus and Rolie-Poly models shows that the onset and size of the elastic lip vortex is governed by a combination of both the degree of shear thinning and the critical shear rate at which the thinning begins. (left) Contour plots of velocity magnitude for the FENE-P model showing the decrease in size of the elastic lip vortex as maximum extensibility decreases. (right) Length of the elastic vortex as a function of a modified Carreau number showing a modelindependent effect of the degree and onset of shear thinning. [ABSTRACT FROM AUTHOR]

ABSTRACT: Introduction. Research of polymer concrete properties show that it differs favorably from conventional concrete by such indicators as mechanical strength, resistance to aggressive impact of various environments, water resistance, abrasion resistance, water-repellency and frost resistance. Currently, it is possible to obtain polymer concrete with characteristic and chemical properties –specified density, strength, deformability, ductility, and corrosion resistance. Methods and materials. The research is carried out by comparing laboratory tests of polymer concrete based on furfural binder. Furfural has a high reactivity and can form resin compounds with many chemicals. Diphenylamine was added to furfural in different proportions. Benzenesulfonic acid, sulfuric acid and their mixture at a ratio – 1:1 by weight were used as hardeners. Crushed sand or ground andesite based on nanostructured microfiller served as aggregate for various compositions of polymer solutions. The polymer concrete strength, chemical resistance, lasting properties, water resistance, abrasion resistance, metal adhesion were tested during the research. Structural changes in properties were studied by the electron microscopic analysis method. Results and discussion. It is established that the diphenylamine solution in furfural, provided that it is solidified by sulfuric acid, benzolsulfoacid or mixture of these acids, is a polymer binder capable to form a high-strength material under normal hardening conditions by acid-resistant aggregates. It is also determined that to prepare resin, the ratio of furfural and diphenylamine should be within 1:0.5–0.3 by weight. The resin containing 1 weight part (w.p.) of furfural and 0.5 weight part of diphenylamine is conventionally named FD-1; containing 1 weight part of furfural and 0.4 weight part of diphenylamine – FD-2 and resin with 0.3 weight part of diphenylamine – FD-3. Conclusion. The introduction of nanostructured microfiller into the polymer concrete composition could save expensive resin. Comparison of the technologies for producing FD resin and polymer concrete, as well as preliminary test data of the studied materials, can determine the possible technical and economic advantages of polymer concrete based on FD resin over the polymer concrete based on FA (furfurolacetone) monomer which is currently used in construction of hydro-engineering structures. Polymer concrete based on FD resin has high strength and exceeds the strength of polymer concrete based on FA monomer by 20–25%.

The weak point of ionic liquids is their high viscosity, limiting the maximum polymer concentration in the forming solutions. A low-viscous co-solvent can reduce viscosity, but cellulose has none. This study demonstrates that dimethyl sulfoxide (DMSO), being non-solvent for cellulose, can act as a nominal co-solvent to improve its processing into a nanofiltration membrane by phase inversion. A study of the rheology of cellulose solutions in diluted ionic liquids ([EMIM]Ac, [EMIM]Cl, and [BMIM]Ac) containing up to 75% DMSO showed the possibility of decreasing the viscosity by up to 50 times while keeping the same cellulose concentration. Surprisingly, typical cellulose non-solvents (water, methanol, ethanol, and isopropanol) behave similarly, reducing the viscosity at low doses but causing structuring of the cellulose solution and its phase separation at high concentrations. According to laser interferometry, the nature of these non-solvents affects the mass transfer direction relative to the forming membrane and the substance interdiffusion rate, which increases by four-fold when passing from isopropanol to methanol or water. Examination of the nanofiltration characteristics of the obtained membranes showed that the dilution of ionic liquid enhances the rejection without changing the permeability, while the transition to alcohols increases the permeability while maintaining the rejection. [ABSTRACT FROM AUTHOR]

Purpose. Determination of the required concentration of polymer solution, providing the maximum well insulation effect, depending on the filtration characteristics of the medium. Methodology. The research was conducted by experimental method using the methodology of planning the experiment. The theory of rational planning was used by varying two variables on five levels. Media permeability and polymer solution concentration were used as variables. Methods of mathematical statistics were used in processing the results. Findings. Experimental studies made it possible to build a model expressing the dependence of the residual resistance factor on the permeability of the medium and the concentration of the polymer solution. By further statistical processing the connection between permeability and necessary concentration of polymer solution was obtained. Originality. The experimental studies have substantiated the possibility of evaluating the influence of medium permeability and concentration of polymer solution on the residual resistance factor and determined its dependence on the concentration of polymer solution and medium permeability. The main point of polymer solutions application is justification and choice of the reagent concentration. The concentration should be selected in such a way that it provides the maximum value of the residual resistance factor and the viscosity of the solution necessary to level out permeability heterogeneity of the environment to some extent. To achieve this, a relationship has been obtained that allows determining the concentration of the polymer solution at a given permeability of the environment that provides the maximum residual resistance factor. Practical value. The conducted experimental studies allow developing the ideas about the regularities of water manifestations. The results of the research allow selecting purposefully both the formulations of composite systems and the technology of their application to improve the efficiency of oil production and to limit water inflows in specific geological and physical conditions. [ABSTRACT FROM AUTHOR]

The shear rheology of particle suspensions in shear-thinning polymeric fluids is studied experimentally using parallel plate measurements and numerically using fully resolved, 3D finite volume simulations with the Giesekus fluid model. We show in our experiments that the steady shear viscosity and first normal stress difference coefficient of the suspension evolve from shear-thickening to substantially shear-thinning as the degree of shear-thinning of the suspending fluid increases. Moreover, in highly shear-thinning fluids, the suspension exhibits greater shear-thinning of the viscosity than the suspending fluid itself. Our dilute body-fitted simulations show that in the absence of hydrodynamic interactions, shear-thinning can arise from the particle-induced fluid stress (PIFS), which ceases to grow with increasing shear rate at low values of β (solvent viscosity ratio) and finite values of α (the Giesekus drag coefficient). In a Giesekus suspending fluid, the polymers surrounding the suspended particle are unable to stretch sufficiently at high Weissenberg numbers (Wi) and the reduced polymer stress results in a lower PIFS. When coupled with the shear-thinning stresslet, this effect creates an overall shear-thinning of the viscosity. We then explore the effects of particle-particle interactions on the suspension rheology using immersed boundary simulations. We show that multiparticle simulations are necessary to obtain the shear-thinning behavior of the per-particle viscosity of suspensions in shear-thinning fluids at moderate values of β. Particle-particle interactions lead to a substantial decrease in the PIFS and an enhancement of the shear-thinning of the stresslet compared to the single particle simulations. This combination leads to the shear-thinning of the per-particle viscosity seen in experiments. We also find that very low values of β and finite values of α have opposing effects on the per-particle viscosity that can lead to a nonmonotonic per-particle viscosity versus shear rate in a highly shear-thinning fluid. Overall, the addition of rigid particles to highly shear-thinning fluids, such as joint synovial fluid, leads to increased viscosity and also increased shear-thinning at high shear rates. [ABSTRACT FROM AUTHOR]

Over the last decade, researchers have investigated the potential of nano and microfiber scaffolds to promote wound healing, tissue regeneration, and skin protection. The centrifugal spinning technique is favored over others due to its relatively straightforward mechanism for producing large quantities of fiber. Many polymeric materials have yet to be investigated in search of those with multifunctional properties that would make them attractive in tissue applications. This literature presents the fundamental process of fiber generation, and the effects of fabrication parameters (machine, solution) on the morphologies such as fiber diameter, distribution, alignment, porous features, and mechanical properties. Additionally, a brief discussion is presented on the underlying physics of beaded morphology and continuous fiber formation. Consequently, the study provides an overview of the current advancements in centrifugally spun polymeric fiber-based materials and their morphological features, performance, and characteristics for tissue engineering applications. [ABSTRACT FROM AUTHOR]

The possibility of obtaining porous films through solutions of polylaurolactam (PA12) in benzyl alcohol (BA) was considered. The theoretical calculation of the phase diagram showed the presence of the upper critical solution temperature (UCST) for the PA12/BA system at 157 °C. The PA12 completely dissolved in BA at higher temperatures, but the resulting solutions underwent phase separation upon cooling down to 120–140 °C because of the PA12's crystallization. The viscosity of the 10–40% PA12 solutions increased according to a power law but remained low and did not exceed 5 Pa·s at 160 °C. Regardless of the concentration, PA12 formed a dispersed phase when its solutions were cooled, which did not allow for the obtention of strong films. On the contrary, the phase separation of the 20–30% PA12 solutions under the action of a non-solvent (isopropanol) leads to the formation of flexible microporous films. The measurement of the porosity, wettability, strength, permeability, and rejection of submicron particles showed the best results for a porous film produced from a 30% solution by non-solvent-induced phase separation. This process makes it possible to obtain a membrane material with a 240 nm particle rejection of 99.6% and a permeate flow of 1.5 kg/m2hbar for contaminated water and 69.9 kg/m2hbar for pure water. [ABSTRACT FROM AUTHOR]

The suitability of industrially significant synthetic oils with dispersed polymeric chains that can be used as dielectric coolants with enhanced heat transfer properties in single-phase immersion cooling for electric vehicle components is evaluated via molecular dynamics simulations (MD). The fluids investigated are a synthetic solvent poly-alpha-olefin (PAO-2) and a solution based on PAO-2 with a single olefin co-polymer (OCP) chain dissolved. The simulation model accurately predicts the experimental thermodynamic properties of PAO-2. The effect of the polymer chain on the structural behaviour of the solution and its relation with the rheological properties is predicted and analysed at various temperatures in the range of 293 K–373 K. It is found that polymer solution shows an average viscosity enhancement of 9.2% and thermal conductivity enhancement of 2% within the temperature range. These properties eventually influence the Weissenberg and Nusselt numbers that impact the heat transfer. Analysis of the hydrodynamic radius of PAO-2 molecules shows that OCP chemistry acts as a thickening agent in the solution. Addition of the polymer chain is also shown to accelerate the shear thinning process due to increase in storage and loss moduli. The terminal relaxation time of OCP decreases with temperature and shear rate. The work conclusively establishes the impact of molecular interactions of the weakly viscoelastic liquids on their macroscopic behaviour. The viscoelastic nature of the examined polymer solution can lead to vortex roll-up in constricted flows inducing heat transfer enhancement. This in turn supports its use in immersion cooling applications which is shown for the first time.

Formation and coalescence of solvent droplets on a thread of polymer solution at the final stage of capillary pinching is studied theoretically. It is considered that macromolecules are already almost completely stretched along the extension axis and their contour length exceeds the diameter of the thread. In this regime, the radius of polymer string decreases slowly with time under the action of capillary forces and the solvent squeezes out to the thread surface forming annular droplets of different sizes. The thinning process stops when the capillary pressure is balanced by the osmotic pressure of the polymer. As a result, a quasistationary two-phase structure of polydisperse solvent droplets on a polymer string is formed. We develop a rigorous theory showing that the polymer core is swollen in the droplet regions but still remains much thinner than the solvent phase. We also demonstrate that such a blistering structure is unstable with respect to droplet coalescence and elucidate two mechanisms of this process due to the solvent flow between the droplets and due to diffusion of solvent droplets along the polymer string. Both mechanisms lead to the same long-time power law (t1/7) for the droplet radius. It is shown that a breakage of the polymer string may occur at time scales exceeding the Rouse time of polymer chains. [ABSTRACT FROM AUTHOR]

Electrospinning is an easy and efficient method for preparing nanofibers on laboratory and industrial scales. In recent years, various studies have been done with special attentions to specific structures, increasing the application and eliminating the shortcomings of previous methods. Janus structure is one of the new and widely used structures that due to the limitations and challenges in achieving this structure, such as nozzle design, phase separation of two polymer solutions during electrospinning, flow rate control, optimal voltage and other parameters, the published reports in this field, are limited. Side-by-side electrospinning is one of the common ways to achieve this special structure. In this method, with appropriate nozzle design, two polymer solutions can be electrospun simultaneously. In addition, the nozzle design and the related parameters such as needle diameter, angle, and distance between the nozzles are of special importance. Also, parameters related to the rheological behavior of the polymer, especially viscosity, are crucial in achieving this particular structure. In this paper, the methods of preparation of Janus nanofibers by side-by-side electrospinning method, new structures based on these nanofibers, including the study of structure and production methods through side-by-side electrospinning, are briefly reviewed.

The present experimental investigation combines the bulk flow properties of polymer solutions and measurable rheological parameters as they flow through a distinctive micro-porous structure, with micro-PIV (micro-particle image velocimetry) to measure the velocity distribution and velocity fluctuations within individual pores of a novel porous glass structure. To investigate the effects of fluid elasticity at pore scale, aqueous solutions of a polyacrylamide (PAA) & polyethylene oxide (PEO) in the concentration range of 50–200 ppm, which were characterized in both shear and extensional flows using shear and capillary break-up extensional rheometers (CaBER) respectively, were used as working fluids. The velocity field measurement includes the velocity magnitude and fluctuation intensity in several different pores within the porous material across a Weissenberg number W i range of approximately 0.01 to 1 for each of the test fluids. The global averaged fluctuation intensity increases with W i but the critical value, which indicates the onset of significant unsteadiness (i.e. well above noise floor/Newtonian baseline) within the flow at pore scale gives an approximately constant value of W i ≈ 0.4, which is almost 40 times higher than the value that is observed in the pressure-drop measurements for the data to rise above the Newtonian base line. We therefore postulate that the enhanced pressure-drop behaviour of the bulk flow may not be due to local velocity fluctuations within the pores but due to mean flow effects, at least over a significant portion of the data (up to W i ≈ 0.4). • Micro-PIV in a porous media reveals velocity field. • Enhanced in pressure drop occurs at significantly lower flowrates than corresponding increase in velocity fluctuations. • Mean flow (steady) effects therefore responsible for pressure rise in this porous media rather than elastic instability. [ABSTRACT FROM AUTHOR]

The phase equilibrium shift caused by changes in polymer-liquid compatibility under the influence of external or internal factors is discussed as the main mechanism of gel formation. Wherein, it is assumed that the gel is a solid, non-flowing soft substance formed due to incomplete phase decomposition of a solution. The sol-gel transition occurs through the intermediate stage of the formation of a viscoelastic yielding medium. The liquid-yielding medium-gel transition results in fundamental changes in the rheological properties of the substance. Therefore, the study of the kinetics of the evolution of rheological properties at various stages of gelation is an important tool for understanding this phenomenon. The review contains a discussion of recent publications and the formulation of some challenging problems. [Display omitted] [ABSTRACT FROM AUTHOR]

A great progress has been made over the last decades in studying concentration scaling on rheometric properties of monodisperse polymer solutions. However, the effects of polydisperse polymer solutions on such a concentration scaling remain elusive. In this work, rheometric properties of industrially relevant polydisperse and high molecular weight polyacrylamide (PAAm) aqueous solution have been studied. The results show a concentration scaling of the characteristic relaxation time, the plateau modulus and the zero-shear viscosity across a concentration range from 10c* to 250c*. The time-concentration superposition principle is validated and extended in the data analysis of the terminal dynamic regime. The concentration scaling exponent of their shifting factors is significantly smaller than the results of monodisperse polymer solutions in good and θ solvents reported in the literature. The steady shear viscosity and shear stress of 18M PAAm aqueous solutions with relatively lower concentration (≤35c*) could also be superimposed into a master curve with the shear-thinning exponent of 0.73±0.03 and 0.27±0.03, respectively, over a wide range of shear rates in about six orders of magnitudes. However, for 18M PAAm aqueous solutions with higher concentration (≥48c*) in an intermediate shear thinning regime, the scaling exponent shows a pronounced concentration dependence. The shear thinning exponent of steady shear viscosity varies from 0.73 to 0.57 as concentration is increased, and then increases from 0.57 to 0.90 from sufficiently high shear rate. Further increasing shear rate, the shear-thinning exponent of 18M PAAm aqueous solutions at all concentrations converges to the lower bounded value observed in the relatively less concentrated (≤35c*) 18M PAAm aqueous solutions, i.e., 0.73±0.02 for shear viscosity and 0.27±0.02 for steady shear stress, respectively. It reveals that the concentration effects of polydisperse polymer solutions could be greatly reduced by the dynamic "molecular individualism" in strong shear flow. [ABSTRACT FROM AUTHOR]

: The construction of composite flooding system based on dynamic covalent bonds is one of the effective methods to improve the salt and temperature resistance of polymer flooding agents. The polymers used in most composite systems are xanthan gum and guar gum. In this paper, a novel multi‐hydroxyl polymer was synthesized, and a new composite system was constructed based on the dynamic boronic ester bonds. Firstly, the multi‐hydroxyl polymer P(AM‐DPMOH2) was prepared by aqueous solution copolymerization of acrylamide (AM) and a dihydroxy monomer 2,3‐dihydroxy‐N‐(3‐methacrylamidopropyl)‐N,N‐dimethylpropan‐1‐aminium (DPMOH2), which was obtained by quaternization reaction between 3‐chloro‐1,2‐propanediol and N‐(3‐dimethylaminopropyl). Then, the composite system was prepared by the P(AM‐DPMOH2) solution and polyboronic acid compound (BPEI). The effects of DPMOH2 content in P(AM‐DPMOH2), molecular weight of P(AM‐DPMOH2), molecular weight of BPEI, phenylboronic acid groups content in BPEI and pH on the formation of thickening composite system were investigated. The results showed that when the content of DPMOH2 in P(AM‐DPMOH2) exceeded 40 wt%, viscosity average molecular weight of P(AM‐DPMOH2) was higher than 5.0×105 g/mol, the molecular weight of PEI in BPEI was larger than 3000 g/mol, the content of phenylboronic acid groups in BPEI was more than 39.3 %, and pH was in the range of 8–9, the thickening composite system can be formed by P(AM‐DPMOH2) and BPEI. In addition, both the temperature and salt resistance of the composite system formed by 3000 mg/L P(AM‐DPMOH2) and 2000 mg/L BPEI was much better than that of 3000 mg/L P(AM‐DPMOH2). The results of this paper provide a new finding of how to construct a composite flooding system with dynamic covalent bonds. [ABSTRACT FROM AUTHOR]

The vapor–liquid equilibrium of the fluorobenzene–polystyrene binary polymer solution at 303.15 K was measured using a static pressure device. The vapor–liquid equilibrium of the fluorobenzene–n-octane–polystyrene ternary solution in a partial concentration range under normal pressure was determined using an improved Othmer equilibrium still, in which the octane concentration was low. Three activity coefficient models, poly-NRTL, UNIQUAC, and M-UNIQUAC-LBY, were utilized to correlate the experimental data of binary and ternary solutions, and the component activities of the fluorobenzene–n-octane–polystyrene solution at 303.15 K were predicted. A mathematical model based on the Stefan flow was developed to simulate the evaporation process of composite spherical droplets. The activity predicted by the activity coefficient model was used for numerical simulations, and compared with simulations using the activity following Raoult’s law. The comparative analysis revealed that simulations based on Raoult’s law and activity coefficient models yielded similar results when the mass fraction of fluorobenzene exceeded 0.6. However, in the later stages of evaporation, the calculations based on Raoult’s law predicted a 10% shorter drying time for fluorobenzene. The activity coefficient models provided a better approximation and exhibited similar droplet diameter shrinking behaviors to the actual evaporation process.

Polymeric materials are ubiquitous in our everyday life, where they find a broad range of uses—spanning across common household items to advanced materials for modern technologies. In the context of the latter, so called “smart polymers” have received a lot of attention. These systems are soluble in water below their lower critical solution temperature Tℓ and often exhibit counterintuitive solvation behavior in mixed solvents. A polymer is known as smart-responsive when a slight change in external stimuli can significantly change its structure, functionm and stability. The interplay of different interactions, especially hydrogen bonds, can also be used for the design of lightweight high-performance organic solids with tunable properties. Here, a general scheme for establishing a structure–property relationship is a challenge using the conventional simulation techniques and also in standard experiments. From the theoretical side, a broad range of all-atom, multiscale, generic, and analytical techniques have been developed linking monomer level interaction details with macroscopic material properties. In this review, we briefly summarize the recent developments in the field of smart polymers, together with complementary experiments. For this purpose, we will specifically discuss the following: (1) the solution processing of responsive polymers and (2) their use in organic solids, with a goal to provide a microscopic understanding that may be used as a guiding tool for future experiments and/or simulations regarding designing advanced functional materials.

Bacteria often live surrounded by polymer solutions, such as in animal respiratory, gastrointestinal, and reproductive tracts. In these systems, polymer solutions are often exposed to fluid flow, and their complex rheology can affect the transport of chemical compounds and microorganisms. Recent studies have focused on the effect of polymer solutions on the motility of bacteria in the absence of fluid flow. However, flow can be a game-changer on bacterial transport, as demonstrated by the depletion of motile bacteria from the low-shear regions and trapping in the high-shear regions in simple fluids, even for flows as simple as the Poiseuille one. Despite the relevance of polymer solutions in many bacterial habitats, the effect of their complex rheology on shear-induced trapping and bacterial transport in flow has remained unexplored. Using microfluidic experiments and numerical modeling, we studied how the shear rate and the rheological behavior of Newtonian and non-Newtonian polymer solutions affect the transport of motile, wild-type Pseudomonas aeruginosa in a Poiseuille flow. Our results show that, in Newtonian solutions, an increase in viscosity reduces bacterial depletion in the low-shear regions at the microchannel center, due to a reduction in the bacterial swimming velocity. Conversely, in the non-Newtonian solution, we observed a depletion comparable to the buffer case, despite its zero-shear viscosity being two orders of magnitude higher. In both cases, bacterial swimming and polymer fluid rheology control the magnitude of bacterial depletion and its shear-rate dependence. Our observations underscore the importance of the rheological behavior of the carrier fluid in controlling bacterial transport, in particular, close to surfaces giving rise to velocity gradients, with potential consequences on surface colonization and biofilm formation in many naturally relevant microbial habitats.

The weak point of ionic liquids is their high viscosity, limiting the maximum polymer concentration in the forming solutions. A low-viscous co-solvent can reduce viscosity, but cellulose has none. This study demonstrates that dimethyl sulfoxide (DMSO), being non-solvent for cellulose, can act as a nominal co-solvent to improve its processing into a nanofiltration membrane by phase inversion. A study of the rheology of cellulose solutions in diluted ionic liquids ([EMIM]Ac, [EMIM]Cl, and [BMIM]Ac) containing up to 75% DMSO showed the possibility of decreasing the viscosity by up to 50 times while keeping the same cellulose concentration. Surprisingly, typical cellulose non-solvents (water, methanol, ethanol, and isopropanol) behave similarly, reducing the viscosity at low doses but causing structuring of the cellulose solution and its phase separation at high concentrations. According to laser interferometry, the nature of these non-solvents affects the mass transfer direction relative to the forming membrane and the substance interdiffusion rate, which increases by four-fold when passing from isopropanol to methanol or water. Examination of the nanofiltration characteristics of the obtained membranes showed that the dilution of ionic liquid enhances the rejection without changing the permeability, while the transition to alcohols increases the permeability while maintaining the rejection.

Over the last decade, researchers have investigated the potential of nano and microfiber scaffolds to promote wound healing, tissue regeneration, and skin protection. The centrifugal spinning technique is favored over others due to its relatively straightforward mechanism for producing large quantities of fiber. Many polymeric materials have yet to be investigated in search of those with multifunctional properties that would make them attractive in tissue applications. This literature presents the fundamental process of fiber generation, and the effects of fabrication parameters (machine, solution) on the morphologies such as fiber diameter, distribution, alignment, porous features, and mechanical properties. Additionally, a brief discussion is presented on the underlying physics of beaded morphology and continuous fiber formation. Consequently, the study provides an overview of the current advancements in centrifugally spun polymeric fiber-based materials and their morphological features, performance, and characteristics for tissue engineering applications.

The paper provides a description of the potential for the direct current- and alternating current-driven electrospinning of various linear aliphatic polyamides (PA). Sets with increasing concentrations of selected PAs were dissolved in a mixture of formic acid and dichloromethane at a weight ratio of 1:1 and spun using a bar electrode applying direct and alternating high voltage. The solubility and spinnability of the polyamides were investigated and scanning electron microscopy (SEM) images were acquired of the resulting nanofiber layers. The various defects of the spun fibers and their diameters were detected and subsequently measured. Moreover, the dynamic viscosity and conductivity were also subjected to detailed investigation. The most suitable concentrations for each of the PAs were determined according to previous findings, and the solutions were spun using a NanospiderTM device at the larger scale. The fiber diameters of these samples were also measured. Finally, the surface energy of the fiber layers produced by the NanospiderTM device was measured aimed at selecting a suitable PA for a particular application. [ABSTRACT FROM AUTHOR]

Theoretical expressions for the intrinsic viscosity, the Huggins coefficient, zero-shear viscosity, and storage and loss moduli for stiff-chain polymer solutions are reviewed. Especially, the mean-field Green function method is explained in detail to consider the intermolecular collision effect on the rheological properties of concentrated stiff-chain polymer solutions, by applying the method to monodisperse and polydisperse straight cylinders and monodisperse fuzzy cylinder models. The theoretical expressions reviewed are compared with experimental results for aqueous solutions of two rigid helical polysaccharides, schizophyllan and xanthan. [ABSTRACT FROM AUTHOR]

Being one of the most commonly performed EOR methods, polymer injection is used to increase the mobility ratio and decrease water relative permeability to allow the injected fluid to sweep more oil towards the production well. Before the polymer solution is injected into the reservoir through the injection wells, the process of polymer injection must be simulated using commercial numerical reservoir simulators. In order to be able to simulate the process, the viscosity behavior of the solution must be known. Therefore, a model is required to estimate the viscosity of the injected fluids versus shear rate and polymer concentration. In this study, a new mathematical function based on the power-law fluid equation is presented, which can be applied to predict the viscosity of SPAM solutions. The two required parameters of the power-law equation are obtained by fitting a power-law function to the viscosity-shear rate data. Samples in different polymer concentrations (using two SPAM polymers with different molecular weights) were prepared and their viscosity was measured against different shear rates. The results were fitted to the power-law equation and their corresponding power-law parameters were recorded. A mathematical function was introduced and tested for each parameter. The new functions combined with the power-law equation were used to estimate the viscosity of different polymer solutions with different SPAM concentrations. The results showed that the model is capable of estimating the viscosity with acceptable precision. Furthermore, it is applicable in various temperatures and water salinities.

Research on energy generation characteristics based on pressure retarded osmosis (PRO) using seawater is being widely carried out. However, there are few studies that use polymer solutions. Therefore, the purpose of this study is to evaluate energy generation characteristics when using a polymer solution. We established a PRO model with a constant hydrostatic pressure difference in a semipermeable membrane, through which pure water permeates into the polymer solution side. The concentration of the polymer solution was determined by solving the one-dimensional convection-diffusion equation, and the osmotic pressure difference in the semipermeable membrane was evaluated. The following four dimensionless parameters were derived by making the basic equations dimensionless; the dimensionless second virial coefficient α, the dimensionless hydrostatic pressure difference p*, the Péclet number Pe, and the cross-sectional area reduction ratio of the tube on the solution side β. The generation characteristics of dimensionless power densities were evaluated by changing the α representing the properties of the polymer solution. The value of p* for which the largest dimensionless power density obtained was 0.5 or more, and approached 1 as α increased. When compared with seawater, the power density while using polymer solution was smaller than that while using seawater. However, by preventing the temporal decrease in the concentration of the polymer solution and the generation of a concentration boundary layer, it is possible to significantly improve the power density and obtain a power density close to that of seawater. In addition, when the membrane used for standard PRO is applied to the present model, a commercial-level power density can be obtained.

The possibility of obtaining porous films through solutions of polylaurolactam (PA12) in benzyl alcohol (BA) was considered. The theoretical calculation of the phase diagram showed the presence of the upper critical solution temperature (UCST) for the PA12/BA system at 157 °C. The PA12 completely dissolved in BA at higher temperatures, but the resulting solutions underwent phase separation upon cooling down to 120–140 °C because of the PA12’s crystallization. The viscosity of the 10–40% PA12 solutions increased according to a power law but remained low and did not exceed 5 Pa·s at 160 °C. Regardless of the concentration, PA12 formed a dispersed phase when its solutions were cooled, which did not allow for the obtention of strong films. On the contrary, the phase separation of the 20–30% PA12 solutions under the action of a non-solvent (isopropanol) leads to the formation of flexible microporous films. The measurement of the porosity, wettability, strength, permeability, and rejection of submicron particles showed the best results for a porous film produced from a 30% solution by non-solvent-induced phase separation. This process makes it possible to obtain a membrane material with a 240 nm particle rejection of 99.6% and a permeate flow of 1.5 kg/m2hbar for contaminated water and 69.9 kg/m2hbar for pure water.

Primitive chain network (PCN) and non-equilibrium molecular dynamics (NEMD) simulations indicate that the nonuniversality seen in the elongational rheology of linear polymer melts and concentrated solutions is caused by monomeric friction reduction. We present, in the context of tube models with varying tube diameter, a new constitutive equation based on enhanced relaxation of stretch (ERS) and find good agreement with experimental evidence and with predictions of the extended interchain pressure (EIP) model. The stretch evolution equations of the ERS and the EIP model can be converted in a form, which allows expressing them in terms of monomeric friction reduction. Monomeric friction coefficients obtained from the ERS model and those used in PCN and NEMD simulations show at least qualitative agreement. While the reduction of monomeric friction is incorporated in PCN and NEMD simulations by empirical correlations between friction coefficient and segmental orientation or elongational stress fitted to elongational viscosity data, the EIP and ERS models provide analytical and parameter-free relations of monomeric friction reduction as a function of chain stretch. [ABSTRACT FROM AUTHOR]

The effect of the addition of triblock copolymer polyethylene glycol (PEG)–polypropylene glycol (PPG)–polyethylene glycol (PEG) (Pluronic F127) and polyethylene glycol (PEG-4000, Mn = 4000 g mol−1) to the polysulfone (PSF) casting solution on the membrane structure and performance was studied. The phase state, viscosity and turbidity of PSF solutions in N,N-dimethylacetamide (DMAc) with the addition of block copolymer Pluronic F127 were investigated. It was found that 18–22 wt.% PSF solutions in DMAc with Pluronic F127 content ≥ 5 wt.% feature a lower critical solution temperature (LCST). Membrane structure was investigated using scanning electron and atomic force microcopies. It was revealed that average pore size and pore amount on the surface of the membrane selective layer increase and pore size distribution becomes wider with an increase in Pluronic F127 content in the casting solution. It was found that the average surface roughness parameters of the membrane selective layer for PSF/Pluronic F127 membranes significantly exceed those for PSF/PEG-4000 membranes. It was shown that the increase in the membrane flux and the decrease in polyvinylpyrrolidone (PVP K-30, Mn = 40,000 g mol−1) rejection are a result of the addition of both Pluronic F127 and PEG-4000 into the casting solution. It was revealed that PSF/Pluronic F127 membranes are characterized by higher pressure resistance in ultrafiltration process, a lower total flux decrease during ultrafiltration of bovine serum albumin solutions. The antifouling performance of PSF/Pluronic F127 membranes was found to exceed significantly the antifouling performance of PSF/PEG-4000 membranes. [ABSTRACT FROM AUTHOR]

In this paper, we study the shear-induced flow of magneto-polymer composites, consisting of dispersions of magnetic particles in solutions of polymers, as a competition between the colloidal forces amid particles and their bulk transport induced by the hydrodynamic forces. For this aim, we analyse the role of different experimental parameters. Firstly, by using only solutions of a well-known anionic polymer (sodium alginate), we provoke a moderate hindering of particle movement, but keeping the liquid-like state of the samples. On the contrary, a gel-like behaviour is conferred to the samples when a cationic polymer (chitosan) is additionally added, which further reduces the particle movement. We analyse the effect of an applied magnetic field, which is opposed to particle transport by hydrodynamic forces, by inducing magnetic attraction between the particles. We perform the analysis under both stationary and oscillatory shear. We show that by using dimensionless numbers the differences between samples and experimental conditions are emphasized. In all cases, as expected, the transport of particles driven by bulk hydrodynamic forces dominates at high values of the shear rate. [ABSTRACT FROM AUTHOR]

Elongational viscosity data of well-characterized solutions of 3–50% weight fraction of monodisperse polystyrene PS-820k (molar mass of 820,000 g/mol) dissolved in oligomeric styrene OS8.8 (molar mass of 8800 g/mol) as reported by André et al. (Macromolecules 54:2797–2810, 2021) are analyzed by the Extended Interchain Pressure (EIP) model including the effects of finite chain extensibility. Excellent agreement between experimental data and model predictions is obtained, based exclusively on the linear-viscoelastic characterization of the polymer solutions. The data were obtained by a filament stretching rheometer, and at high strain rates and lower polymer concentrations, the stretched filaments fail by rupture before reaching the steady-state elongational viscosity. Filament rupture is predicted by a criterion for brittle fracture of entangled polymer liquids, which assumes that fracture is caused by scission of primary C-C bonds of polymer chains when the strain energy reaches the bond-dissociation energy of the covalent bond (Wagner et al., J. Rheology 65:311–324, 2021). [ABSTRACT FROM AUTHOR]

A new pressure sensor array, positioned on the bottom plate of a standard torsional rheometer, is presented. It is built from a unique piezo-capacitive polymeric foam and consists of 25 capacitive pressure sensors (of surface 4.5 × 4.5 mm 2 each) built together in a 5 × 5 regular array. The sensor array is used to obtain a mapping of the normal stresses in complex fluids, which dramatically extends the capability of the rheometer. We demonstrate this with three examples. First, a pressure profile is reconstructed in a polymer solution, which enables the simultaneous measurement of the first and the second normal stress differences N 1 and N 2 , with a precision of 2 Pa. In a second part, we show that negative pressures can also be measured. Finally, we focus on the normal stress fluctuations that extend both spatially and temporally in a shear-thickening suspension of cornstarch particles. We evidence the presence of a unique heterogeneity rotating very regularly. In addition to their low cost and high versatility, the sensors show here their potential to finely characterize the normal stresses in viscosimetric flows. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) represent efficient energy storage technology that can help to alleviate fossil fuel-based CO2 emissions. Presently, LIBs are being applied extensively in consumer electronics and electric vehicles, but because of limited resources, there is an urgent need for spent LIB recycling technologies. The complexity of LIBs, especially the electrode part, makes it difficult to achieve precision separations for each single component from the used electrode with low emissions. Herein, we propose a three-step treatment for the separation of cathode components. In detail, detaching of the current collector from the cathode is accomplished by the solvent method, which was found to be an ideal strategy compared with previous reports. Then, a thermal treatment is used to remove the polymer binder in the second step because we demonstrated that it is challenging to separate polyvinylidene fluoride (PVDF) from other cathode components by dissolution with N-methylpyrrolidone. The separation efficiency between the active material and conductive carbon by the polymer solution in the third step showed reasonably good results. We anticipate this work will serve as an important reference for the separation of each single electrode component in both laboratory- and industrial-scale applications. Separation of binder and development of novel binders, which can be easily recycled for sustainable LIBs, are fruitful areas for further research. [ABSTRACT FROM AUTHOR]

The criterion for brittle fracture of entangled polymer liquids [Wagner et al., J. Rheol. 62, 221–223 (2018)] is extended by including the effects of finite chain extensibility and polymer concentration. Crack initiation follows from rupture of primary C–C bonds, when the strain energy of entanglement segments reaches the energy of the covalent bond. Thermal fluctuations will concentrate the strain energy on one C–C bond of entanglement segments, leading to bond scission and rupture of polymer chains followed by crack initiation and fast crack growth. In start-up flows, entanglement segments characterized by long relaxation times, i.e., predominantly those in the middle of the polymer chain, will be the first to reach the critical strain energy and will fracture. Recent experimental data of Huang [Phys. Fluids 31, 083105 (2019)] of fracture of a monodisperse polystyrene melt and of several solutions of monodisperse polystyrenes dissolved in oligomeric styrene are in agreement with the scaling relations for critical Weissenberg number as well as Hencky strain and stress at fracture derived from this fracture criterion and the extended interchain pressure model [Narimissa, Huang, and Wagner, J. Rheol. 64, 95–110 (2020)]. [ABSTRACT FROM AUTHOR]

Dust exposure is a serious threat to human health due to dermal contact, inhalation, and ingestion. Children are more vulnerable to dust than adults as a result of high rates of unintentional, or deliberate, ingestion and inhalation of dust. In this study, dust reduction in the playground due to coating of the soil particles with a PVA/PVAc-based solution was investigated. Soil particles were coated with varying amounts of coating solution and the samples were examined for various parameters e.g., specific density, moisture content, liquid and plastic limits, permeability, dust generation due to wind effect and human activity. The results demonstrated that coated soil samples showed improved permeability characteristics and reduced dust generation. These characteristics were improved by increased content of coating solution. [ABSTRACT FROM AUTHOR]

We study buffered aqueous solutions of deoxyribonucleic acid isolated from bacteriophage lambda (λ-DNA) at shear rates up to 105 s−1. The shear rates are accessed with a narrow-gap rheometer at gap widths down to 20 μm. At lower shear rates, our data merge with the literature values. At high shear rates, the viscosity levels off into an infinite-shear viscosity plateau. Hence, the viscosity functions of buffered aqueous DNA solutions are now available for the entire shear-rate range from the first Newtonian plateau to that of infinite-shear viscosity. The latter hardly differs from the solvent viscosity. For the normal-stress differences, we observe a power-law dependence on the shear rate close to previous findings up to shear rates of about 104 s−1. Beyond this shear-rate range, we observe a stepwise change with the shear rate. By means of agarose gel electrophoresis, we confirm that the λ-DNA is not fragmented during our rheometric study at high shear rates. Yet, at the highest shear rates studied, shear-induced changes in the DNA to structures not being able to travel through the gel appear. [ABSTRACT FROM AUTHOR]

An experimental study of the rise in the temperature of a water–polymer jet, which occurs in hydrocutting and is caused by the Joule–Thomson effect, has enabled the authors to propose a method to enhance the process of hydrojet water–polymer cutting of materials. [ABSTRACT FROM AUTHOR]

Piperine-rich herbal mixture (PHM) used in this study is a traditional Thai medicine that contains 21 oriental herbs. It is called “Sahastara remedy” and is officially included in the Thai National List of Essential Medicine since A.D. 2011. PHM has been used orally to relieve muscle and bone pains. It contains Piper nigrum fruits as a major constituent and also Piper retrofractum fruits, PHM thus has anti-inflammatory activities that mostly come from the bioactivities of piperine consisting of these pepper fruits. Unfortunately, PHM usually causes gastrointestinal side effects. Consequently, a topical product containing an alcoholic extract of PHM (PHM-E), i.e., film-forming solution (FFS) was developed to overcome this drawback. The aims of this study were to investigate the anti-inflammatory activity of PHM-E, to evaluate physicochemical properties and the anti-inflammatory activity of FFS containing PHM-E (PHM-E FFS). Anti-inflammatory activities of PHM-E were investigated in the RAW 264.7 cells. Physicochemical properties, in vitro toxicities and anti-inflammatory activities of PHM-E FFS including its dry film (PHM-E film) were determined. PHM-E showed anti-inflammatory activities with dose dependent manners via inhibition of nitric oxide and prostaglandin E2 production by the RAW 264.7 cells and promotion of the cell phenotype polarization from M1 to M2. PHM-E FFS had low viscosity and exhibited the Newtonian behavior. It provided elastic PHM-E film with low tensile strength. The release profile of piperine from PHM-E film followed a zero-kinetic model. PHM-E FFS demonstrated compatibility with the skin cells, minimal ocular irritant when accidentally splashing into the eye and moderate-to-high potency for inhibition of inflammatory symptoms in the rats. PHM-E FFS thus had potential for use in the further clinical study to investigate its efficacy and safety in patients.

The development of analytical methods for viscoelastic fluid flows is challenging. Currently, this problem has been solved for particular cases of multimode differential rheological equations of media state (Giesekus, the exponential form of Phan-Tien-Tanner, eXtended Pom-Pom). We propose a parametric method that yields solutions without additional assumptions. The method is based on the parametric representation of the unknown velocity functions and the stress tensor components as a function of coordinate. Experimental flow visualization based on the SIV (smoke image velocimetry) method was carried out to confirm the obtained results. Compared to the Giesekus model, the experimental data are best predicted by the eXtended Pom-Pom model.

In this study, the effects of a water soluble acrylamide polymer solution (PS) treatment on the index properties, compacted properties, free swelling, stress–strain relationship and compressive strength of an expansive CH soil obtained from the field in Houston, Texas was investigated. In order to characterize the clay before and after polymer treatment X-ray diffraction analyses and Thermogravimetric analyses were used respectively. In addition to characterizing the behavior of expansive CH soil (free swelling of 15%), the effect of treating the soil with a acrylamide PS was investigated and the performance was compared to 6% lime treated soil cured for 7 days at 25 °C and 100% relative humidity before testing. In treating the soil, PS content was varied up to 20% (by dry soil weight) using three different mixes (polymer content) and the soil samples were cured for 1 day at 25 °C and 100% relative humidity before testing. When the CH soil was treated with 10% PS, the liquid limit (LL) and plasticity index (PI) (index properties) of the expansive soil decreased by 33% and 57% respectively. The free swelling of the expansive soil decreased by 60% and the compacted (ASTM 698 standard method) compressive strength increased from 126 to 496 kPa. Polymer treatment also increased the compacted maximum dry density and reduced the optimum moisture content of the treated CH soil. The behavior of the LL, PI and swelling of the expansive soil treated with different percentages of the PSs have been quantified using the Vipulanandan property correlation model. Compressive stress–strain relationships of the expansive soil treated separately with lime and PS have been modelled using the nonlinear Vipulanandan p–q stress–strain model. The stress–strain model parameters were sensitive to the polymer content and the type of treatment. [ABSTRACT FROM AUTHOR]