Low Polymer Concentrations Research Articles

Uniform and Intense Cooling During Hardening Steel in Low Concentration of Water Polymer Solutions

The possibility of decreasing water polymer concentration, decreasing alloy elements in steel, decreasing distortion of steel parts, and increasing service life of machine components and tools during quenching is widely discussed in this paper based on achievements of modern physics. Instead of quenching alloy steel in oils or high concentration of water polymer solutions, the accelerated quench process of optimal hardenability steel in water low concentration of inverse solubility polymers is proposed. Physics of the new approach and new technologies is explained by the author. The creation of a thin polymeric insulating layer during quenching steel in low concentration of inverse solubility polymers decreases initial heat flux density below its critical value that is reason for absence the film boiling process. Due to this fact, full film boiling during quenching is completely absent allowing use optimal hardenability steel instead of alloy steels containing costly alloy elements. Accelerated cooling provided by low concentration of water polymer solution results in creation of high surface compression residual stress, and super strengthening of material that in turn increases service life of machine components and tools. It is underlined in the paper that along with the use of a thin polymeric insulating layer, the resonance effect can be used for destroying the full film boiling process based on implementation different kinds of hydrodynamic emitters. The proposed new technology saves materials, increases service life of steel parts, and improves environment condition in heat treating industry. The patented technologies and processes can be used by engineers and scientists. and can bring great benefits if widely implemented in the practice.

Synthesis and properties composites zeolite/polyaniline of the doping sulfuric acid

Polyaniline and polyaniline-mineral composites on the base of zeolite with low polymer content have been synthesized chemically methods. The formation of composites zeolite/polyaniline was confirmed by results of X-ray phase, FTIR spectral and thermogravimetric analysis. The comparative analysis spectral, thermal and electrical properties of the synthesized samples of polyaniline and composite zeolite/polyaniline has been carried out. It was shown that the structure of samples of polyaniline synthesized is amorphous. The structure of polyaniline in composites zeolite/polyaniline is also mainly crystalline-amorphous with the inclusion of crystalline particles of zeolite as matrices on which particles of polyaniline in the form of emeraldine salt of sulfate acid are formed. It was found that weak interphase interaction between macromolecule of polyaniline and particles of zeolite is possible thanks to interaction hydrogen bonds between surface hydroxy groups of zeolite and imino atoms of the macromolecular chains of polyaniline. The thermal stability of composites zeolite/polyaniline is much higher than pure polyaniline, due to the content of zeolite in the composite. It was established that the electrical conductivity of chanically synthesized samples of polyaniline and composites zeolite/polyaniline is several times higher than the electrical conductivity of chemically synthesized samples. The physico-chemical analysis of samples properties has been carried out using a Dron-5-04 diffractometer (Cu Kα radiation; l=1.54060 Å) in the reflection mode. Fourier-transform infrared (FTIR) spectrа of powders sample were recorded in the range of 4 000–650 cm –1 using a NICOLET IS 10 ATR spectrophotometer in the mode of reflection, which was later transformed into transmission mode. Thermal properties of synthesized samples has been analyzed using Q 1 500-D Derivatograph (MOM Paulik - Paulik - Erdei , Hungary) in the temperature range of 20–900 °C under a heating rate of 10 K/min in the atmosphere of air (corundum crucibles; standard – Al 2 O 3 ; weight of samples – 100 mg). The electrical conductivity of the pelleted samples was determined by measuring their resistance in the "sandwich" type cells at a temperature of 293±1 K using a Rigol DM 3 068 set of equipment for resistance measuring. Keywords: synthesis, polyaniline, zeolite, composite, structure, thermal stability, conductivity.

Influence of water-soluble nonionic polymers adsorption on colloidal properties of nanosilica dispersions

The relationships between the adsorption of poly(vinyl alcohol) (PVA), poly(ethylene oxide) (PEO), and poly(vinyl pyrrolidone) (PVP) of various molecular weights onto nanosilica and the stability and rheological properties of the aqueous dispersions were analyzed. The adsorption isotherms for the polymers correspond to the Langmuir-type isotherms. The adsorption maximum slightly increases with increasing molecular weight of the polymers. The sedimentation and aggregative stability of the silica dispersion decreased at a low amount of an adsorbed polymer (less than a monolayer). At this polymer content, a significant increase in the viscosity of dispersions is observed due to the formation of polymeric bridges between silica nanoparticles from neighboring aggregates of them. If the amount of adsorbed polymer exceeds the monolayer then the stabilizing effect is observed due to the steric factor preventing the bridge formation and the viscosity of dispersion decreases slightly compared with systems with a low polymer content.

Rheological Properties of Chitosan Succinimide in Water-Glycerol Mixed Solvent

Rheological behavior of chitosan succinimide in water-glycerol mixed solvent was studied. Partial replacement of water by glycerol leads to an increase in the complex viscosity of the polymer in solution, to the formation of the network of intermolecular linkages and transition of the system to the gel state at a lower polymer concentration, to a decrease in the polymer concentration in the solution at which the storage modulus becomes higher than the loss modulus, and to an increase in the relaxation time. The systems formed in the process exhibit the viscosity characteristics stable in time and allow preparation of water-insoluble gel-like materials suitable as a base for soft drug forms.

FORMULATION OF POLYMERIC NANOSUSPENSION CONTAINING PRAMIPEXOLE DIHYDROCHLORIDE AND HESPERIDIN FOR IMPROVED TREATMENT OF PARKINSON’S DISEASES

Aims and Objectives: The present study is to formulate the nanosuspension containing a hydrophilic drug pramipexole dihydrochloride and hesperidin and to increase the drug entrapment efficiency.Methods: Hesperidin and pramipexole dihydrochloride loaded in chitosan nanosuspension is prepared by ionic gelation method using chitosan and tripolyphosphate. There was no incompatibility observed between the drug and polymer through Fourier transform infrared and differential scanning calorimetric. Various other parameters such as particle size, zeta potential, scanning electron microscope, drug content, drug entrapment efficiency, and in vitro release have been utilized for the characterization of nanoparticles.Results and Discussion: The average size of particle is 188 nm; zeta potential is 46.7 mV; drug content of 0.364±0.25 mg/ml; entrapment efficiency of 72.8% is obtained with HPN3 formulation. The PHC1 shows the highest drug release followed by PHC2 due to low concentration of polymer and PHC4 and PHC5 show less drug release due to high concentration of polymer. The in vitro release of PHC3 is 85.2%, initial the burst release is shown which is approximately 60% in 8 h; then, slow release later on drastic reduction in release rate is shown in 24 h. The in vivo study histopathological report confers the effective protective against rotenone induces Parkinson’s.Conclusion: PHC3 was chosen as the best formulation due to its reduced particle size and controlled release at optimum polymer concentration which may be used to treat Parkinson’s disease effectively..

Surfactant modulated interaction of hydrophobically modified ethoxylated urethane (HEUR) polymers with impenetrable surfaces

HypothesisThe presence of surfactant modulates the surface-chemistry-specific interaction of hard colloidal particles (latex) with HEUR polymers, principally through introducing a preferential solution interaction rather than a competitive surface interaction; addition of surfactant leads to a preponderance of polymer/surfactant solution complexes rather than surface-bound complexes. ExperimentsA range of model formulations comprising a hexyl end-capped urethane polymer (C6-L-(EO100-L)9-C6), sodium dodecylsulfate (SDS) and a series of polystyrene-butylacrylate latices (PS-BA-L) have been characterised in terms of rheology, particle surface area (solvent relaxation NMR), polymer conformation (small-angle neutron scattering) and solution composition to build up a detailed picture of the distribution of the HEUR in the presence of both surfactant and latex. FindingsThere is very weak adsorption of C6-L-(EO100-L)9-C6 to only the most hydrophobic latex surface studied, an adsorption that is further weakened by the addition of low levels of surfactant. Macroscopic changes in the hydrophobic latex system may be interpreted in terms of bridging flocculation at low polymer concentrations. No adsorption of C6-L-(EO100-L)9-C6 is observed in the case of hydrophilic surfaces. In most cases, the observed behaviour of the ternary system (polymer/surfactant/particle) is highly reminiscent of the binary (polymer/surfactant) system at the appropriate composition, suggesting that the polymer/surfactant solution interaction is the dominant one.

Investigation on the electrospun PVDF/NP-ZnO nanofibers for application in environmental energy harvesting

PVDF is one of the most widely used dielectric polymers that has four phases. Among them, only its β phase shows piezoelectric property, which is accessible through an electrospinning synthesis method. In this research, a solution of dimethylformamide (DMF) and tetrahydrofuran (THF), with different ratios, and two different polymer concentrations, as well as various ZnO percentages, were used for synthesis of PVDF/NP-ZnO nanofibers composite. The samples that led to the formation of nanofibers were characterized. The results indicate that nanofibers were appropriately formed at lower concentrations of polymer and zinc oxide with equal ratio of the two solvents. To study the effects of synthesis conditions on the morphology and diameter of the nanofibers, the samples were synthesized at different intervals and at different injection rates. The results show that at lower intervals, the injection rate should be reduced to form more uniform nanofibers without nodes and sprays. Finally, flexible piezoelectric nanogenerators were fabricated based on the best samples and were tested under vibrational mechanical forces. The results indicate a maximum output power of 32nW/cm2. The greater output current and voltage were resulted by using more uniform and stretched nanofibers.

Polyurethanes as New Excipients in Nail Therapeutics.

Onychomycosis affects about 15% of the population. This disease causes physical and psychosocial discomfort to infected patients. Topical treatment (creams, solutions, gels, colloidal carriers, and nail lacquers) is usually the most commonly required due to the high toxicity of oral drugs. Currently, the most common topical formulations (creams and lotions) present a low drug delivery to the nail infection. Nail lacquers appear to increase drug delivery and simultaneously improve the effectiveness of treatment with increased patient compliance. These formulations leave a polymer film on the nail plate after solvent evaporation. The duration of the film residence in the nail constitutes an important property of nail lacquer formulation. In this study, a polyurethane polymer was used to delivery antifungals drugs, such as terbinafine hydrochloride (TH) and ciclopirox olamine (CPX) and the influence of its concentration on the properties of nail lacquer formulations was assessed. The nail lacquer containing the lowest polymer concentration (10%) was the most effective regarding the in vitro release, permeation, and antifungal activity. It has also been demonstrated that the application of PU-based nail lacquer improves the nail plate, making it smooth and uniform and reduces the porosity contributing to the greater effectiveness of these vehicles. To conclude, the use of polyurethane in nail formulations is promising for nail therapeutics.

Ordered porous conjugated poly(p-phenylene)s films self-assembled through alcohol-controlled breath figure method

Because of their wide applications, the polymer porous films with regular patterned structure have attracted more and more attention. Herein, the porous films created from the poly(p-phenylene)s/CHCl3 solutions have been self-assembled in an alcohol-water mixed vapor atmosphere. The results show that the patterns of the films depend on the polymer concentration and the ratio of alcohols to water. The introduction of a small amount of alcohols can improve the regular pore patterns of the porous films. Using the mixed water/methanol droplets as soft templates, the ordered porous films can be obtained from a high-concentration polymer solution. The low-concentration polymer solution and a high ratio of alcohol to water lead to form large pores in the films. The alcohol-controlled breath figure method is a facile way to design and fabricate ordered porous films based on a conjugated polymer.

A Novel Thermoresponsive Gel as a Potential Delivery System for Lipoxin

The objective of this study was to evaluate a novel thermoresponsive polyisocyanopeptide (PIC)–based hydrogel as an injectable carrier for local drug delivery for periodontal applications. Three formulations of PIC gels, 0.2%, 0.5%, and 1% w/w, were prepared. As controls, commercially available poloxamer 407 (P407) gels of 20% and 26% w/w were used. Lipoxin A4 (LXA4), a proresolving drug, was suspended into the gel solutions. The systems were evaluated regarding dynamic mechanical properties, injectability and stability, release and bioactivity of LXA4, and cytocompatibility. Results showed that the gelation temperatures of PIC and P407 gels were around 13°C to 23°C. PIC gels were less viscous and mechanically weaker than P407 gels due to the low polymer concentrations. However, PIC gels kept gel integrity for at least 2 wk when incubated with phosphate-buffered saline, whereas P407 gels were disintegrated totally within 1 wk. LXA4 was chemically stable in both neutral and alkaline medium for over 1 mo. The release of LXA4 from either 1% PIC or 26% P407 gels depicted an initial burst release followed by a sustained release for around 4 d. The extent of burst release was negatively correlated to the polymer concentration. LXA4 remained bioactive after release from PIC gels. No cytotoxicity was observed for 1% PIC gel. However, 26% P407 inhibited periodontal ligament cell and gingival epithelial cell growth. In conclusion, the thermoresponsive PIC gel is a potential candidate for periodontal drug delivery.

Specific formation of hydrophobic aggregates of ionic thermoresponsive polymers with oppositely charged ionic surfactants under extremely dilute conditions

Cationic and anionic thermoresponsive polymers were synthesized and the formation of their hydrophobic aggregates with ionic surfactants was studied at extremely low polymer concentrations. Alongside the hydrophobic interactions, electrostatic interactions between the ionic groups of the polymers and surfactants played a major role in the formation of the hydrophobic aggregates. In the absence of an ionic surfactant, extremely dilute (i.e., 0.01 wt %) polymer solutions did not become turbid, even when they were heated above the phase-transition temperature. However, above the phase-transition temperature, the polymer solutions became turbid upon the addition of a specific concentration of an ionic surfactant with the opposite charge. In contrast, no increase in the turbidity was observed when an ionic surfactant with the same charge was added to the solution, regardless of the concentration of the ionic surfactant. Even below the phase-transition temperature, the application of a fluorescent probe that responded to the hydrophobicity of its environment revealed that the ionic thermoresponsive polymers formed a hydrophobic environment with oppositely charged surfactants owing to the electrostatic and hydrophobic interactions, even though hydrophobic precipitates were not observed. Thus, the electrostatic interactions between polymers and surfactants played crucial roles in the formation of hydrophobic aggregates under extremely low concentration of the polymers as well as the hydrophobic interactions did.

Self-Assembly and Hydrogelation of Coil–Sheet Poly(l-lysine)-block-poly(l-threonine) Block Copolypeptides

This study reports the self-assembly and hydrogelation of coil–sheet poly(l-lysine)-block-poly(l-threonine) (PLL-b-PLT) block copolypeptides. Our experiments showed that the PLL-b-PLT block copolypeptides with degrees of polymerization (DPs) between 30 and 60 can self-assemble to form fibrils due to the packing of sheetlike PLT at low polymer concentrations; moreover, further increasing the polymer concentration can result in the formation of transparent hydrogels due to fibril entanglements. The hydrogelation was determined by the orientation and packing of the fibril assemblies, which aremainly dictated by the balance between the intermolecular hydrogen bonding interactions and charge repulsion exerted respectively by sheetlike PLT and positively charged, coil PLL segments. The noncovalent interactions can be manipulated by varying the polypeptide chain length and composition, which would result in these block copolypeptides exhibiting different critical gelation concentrations (CGCs), gel molecular ass...

Stable and unstable miscible displacement of a shear-thinning fluid at low Reynolds number

We present the results of experiments performed for the displacement of an aqueous low-concentration polymer solution that initially fills a capillary tube (diameter < 1 mm), using water. Aqueous carboxymethyl-cellulose polymer solutions were prepared at initial concentration 0.5 < c0 < 0.75 (w/w). Polymer concentrations are low such that the displaced fluids may be considered shear-thinning. We measured the shear viscosity of the aqueous polymer solutions and obtained values for Carreau shear-thinning fluid model parameters at each polymer concentration. Separately, we measured the average bulk diffusivity for each solution. The estimates of the residual film using penetrating fluid tip and mean velocities were measured as a function of the Peclet (Pe), Reynolds (Re), Carreau (Cu0), and viscous Atwood number based on zero shear-rate viscosity (At0) where the latter two were computed using c0. For Cu0 > 1, we observe a corkscrew type instability where the wavelength increases as diffusion is diminished but requires a finite amount of diffusion to appear.

Ion Gel Network Formation in an Ionic Liquid Studied by Time-Resolved Small-Angle Neutron Scattering.

We report the time-resolved small-angle neutron scattering (SANS) study of tetra-arm poly(ethylene glycol) (TetraPEG) polymer network formation in a typical ionic liquid (IL), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C2mim][TFSA]). To observe time-dependent SANS profiles, the reaction rate for the AB-type cross-end coupling reaction of TetraPEG macromers was controlled by adding an analogous protic IL, 1-ethylimidazolium TFSA ([C2imH][TFSA]). At polymer concentrations higher than the overlap concentration ( c*), the SANS profile remained unchanged during the gelation reaction, indicating that the network structure was independent of macromer connectivity in a semidiluted solution. On the other hand, at low polymer concentrations, an increase in the SANS profile intensity was clearly observed. The correlation length (ξ), estimated by a fitting analysis based on the Ornstein-Zernike function, increased as the reaction proceeded. This result indicated that the sparsely dispersed macromers formed clusters during the cross-linking process and polymer size growth followed thereafter. We found that the network formation process and homogeneity of the network structure were strongly dependent on the polymer concentration in IL solutions.

Morphology, Rheology, and Kinetics of Nanosilica Stabilized Gelled Foam Fluid for Hydraulic Fracturing Application

Stabilizing mechanism of silica nanoparticles on gelled foam prepared with a very low concentration of polymer (xanthan gum) and surfactant (α-olefin sulfonate) is reported in the present study. The morphology of the foam at optimized composition reveals its improved stability, owing to the adsorption of silica nanoparticles on the bubble interface, which was further confirmed by microscopic images. The foam decay experiments confirmed the slower drainage of liquids through the strong and rough bubble interface in the presence of nanoparticles. The synergistic effects of nanoparticles–polymer–surfactant help to improvise rheology, viscoelastic properties and enhanced static proppant suspension capacity of the foam. Addition of nanoparticles helps in reducing the polymer concentration in the foam fluid without compromising in stability criterion. Thus, the prepared gelled foam offers less formation damage with improved rheology, and proppant carrying capacity without any limitation to low-temperature appli...

DEVELOPMENT AND CHARACTERIZATION OF NOVEL HERBAL FORMULATION (POLYMERIC MICROSPHERES) OF SYZYGIUM CUMINI SEED EXTRACT

Objective: The purpose of the present investigation was to develop and characterize a novel herbal formulation (polymeric microspheres) of Syzygium cumini seed extract.Methods: The extract-loaded microspheres using biological macromolecule ethyl cellulose (EC) was prepared by o/w emulsion solvent evaporation technique using polyvinyl alcohol (PVA) emulsifier. The effect of various process and formulation variables (stirring speed, evaporation time, drug/polymer ratio and organic/aqueous phase ratio) on the properties of microspheres was evaluated.Results: Micromeritic properties indicated good flow properties, and scanning electron microscopy (SEM) confirmed the spherical nature of the prepared microspheres. The particle size and entrapment efficiency were varied between 34.25 to 176.25 µm and 10.51 to 42% depending upon the variables. All the formulations showed minimal drug release in an acidic environment (pH 1.2) confirming the prevention of drug release in the stomach and enteric nature of the polymer. Sustained drug release has been observed in alkaline dissolution media (pH 7.4) after 12 h of drug release study except for formulation F7 which contains a lower concentration of polymer. The fourier transform infrared spectroscopy (FTIR) analysis indicated the compatibility of the extract with the polymer. The absence of extract-polymer interaction was indicated by the differential scanning calorimetry (DSC) thermogram. x-ray diffraction (XRD) analysis revealed the amorphous nature of the extract in the microspheres which in pure form exhibits a crystalline structure.Conclusion: The findings of this present study suggest that microsphere formulation was a promising carrier for novel delivery of herbal drugs.

Robust superhydrophobic electrospun membrane fabricated by combination of electrospinning and electrospraying techniques for air gap membrane distillation

Membrane pore wetting is the main problem hindering long term stability of permeate flux quality in membrane distillation (MD) applications. A superhydrophobic membrane with micro and nanostructured surface features can offer a unique solution to resolve this issue. Thus, a modified electrospun membrane was fabricated using a combination of electrospinning and electrospraying. The membrane surface hydrophobicity was enhanced by constructing a beaded structure from spraying a mixture of non-fluorinated alumina (Al2O3) nanoparticles (NPs) mixed with low concentration of PVDF polymer on an electrospun base membrane made from PVDF. The results revealed that a rough surface with a hierarchical structure can be constructed, which could not only enhance the membrane hydrophobicity, but also further enhance the permeate efficiency by improving parameters such as flux and rejection. Additionally, the membrane hydrophobicity could be further tuned by controlling the bead spinning volume. Our study shows that the modified membrane with 7.8 μm beads layer thickness has boosted the liquid entry pressure (LEP) by 61% from 15.5 psi and the water contact angle to 154°. The performance of modified membranes with different spraying volume (1–5 ml) along with the neat electrospun and commercial membranes were examined in an air gap membrane distillation (AGMD) application for 5 h using a 2.5 wt% of synthetic heavy metal solution as a wastewater model. Then, the optimized superhydrophobic membrane with 2 ml spinning volume (ES15–2) was further tested in comparison with the commercial membrane during long-term operations (30 h) using 3.5 wt% of mixed heavy metals. The flux was 18.67 LMH (l m−2 h−1) for modified membrane (ES15–2) compare with 12.62 LMH for commercial PVDF membrane during 30 h of long-term operation with feed and coolant temperature at 60 °C, 20 °C, respectively. The present superhydrophobic membrane fabricated by a combined electrospinning/electrospray method shows high potential for MD applications.

Carrageenan polysaccharides and oligosaccharides with distinct immunomodulatory activities in murine microglia BV-2 cells

This study was to investigate the anti-inflammatory activities in vitro of various carrageenans (Car) fractions (κ-, ι-, and λ-types) with well characterized molecular properties, using murine microglia BV-2 cell line treated with lipopolysaccharide (LPS) as model. It is indicated that pretreatments with the oligosaccharide fractions from κ- or ι-carrageenan acid hydrolysates (κ- and ι-CarAOS, respectively) at 125–500 μg/mL significantly and dose-dependently decreased the levels of tumor necrosis factor α (TNF-α) secreted from LPS-treated BV-2 cells, showing promisingly anti-inflammatory effects. Differently, pretreatments of most of polymeric carrageenans at 250–500 μg/mL significantly increased the TNF-α level, implying the co-inflammatory effects with LPS. The co-inflammatory effectiveness of pure carrageenans at 125 μg/mL was notable for λ-Car, followed by ι-Car, and insignificantly for κ-Car. Generally, cytokine TNF-α was a more sensitive biomarker to the presence of carrageenans than was the IL-6. The TNF-α level varied greatly at a low carrageenan concentration (125 μg/mL) and high polymer percentage (e.g. purified κ- and ι-Car). Conclusively, the anti-inflammatory effects on LPS-treated BV-2 cells could be attenuated by pretreatments with κ- and ι-CarAOS at 125–500 μg/mL.

Smartwater Synergy With Chemical Enhanced Oil Recovery: Polymer Effects on Smartwater

Summary The synergy between various enhanced-oil-recovery (EOR) processes has always been raised as a potential optimization route for achieving a more-economic and more-effective EOR application. In this study, we investigate the possible synergy between polymer and smartwater flooding for viscous-oil recovery in carbonates. Although the potential for such synergy has been suggested and researched in the literature, we investigate this possibility in a more-realistic framework: part of the development of an EOR portfolio for a slightly viscous Arabian heavy-oil reservoir. In this work, we study the possible synergy between smartwater and polymer flooding by performing rheological, electrokinetic potential (ζ-potential), contact-angle, interfacial tension (IFT), and recovery experiments. Rheological tests, as expected, demonstrated the possibility of achieving the same target viscosity at lower polymer concentrations. With smartwater, the polymer concentration required to achieve a target viscosity of 11 mPa·s was found to be one-third lower than that with normal high-salinity injection water. Electrokinetic-potential and contact-angle results demonstrated that polymer presence has negligible to slightly favorable effect on wettability alteration induced by smartwater. On synthetic calcite surfaces, polymer showed negligible effect, whereas on reservoir-rock surfaces, polymer resulted in further reduction in contact angles beyond that obtained with smartwater. Coreflooding experiments conducted at reservoir conditions with finite smartwater/polymer slugs—besides yielding comparable performance to surfactant/polymer flooding—demonstrated the enhanced performance of smartwater/polymer compared with either of these individual processes. A combined smartwater/polymer process was able to recover substantial additional oil—6.5 to 9.9% original-oil-in-core (OOIC)—above that obtained with either of the two processes when applied independently. Ultimate recoveries from the application of smartwater/polymer (70% OOIC) were quite comparable to, and actually slightly higher than, that of surfactant/polymer (67% OOIC). However, in terms of the remaining oil in core (ROIC) after polymer flooding, both processes (smartwater/polymer and surfactant/polymer) exhibited quite similar incremental recoveries of 20.6 and 20.5% OOIC, respectively. The results of this work clearly demonstrated the potential synergy between smartwater and polymer flooding—beyond that of the well-established polymer-viscosity enhancement—for a realistic scenario. The additive effect of smartwater was successfully shown to combine with polymer to increase oil recovery, in addition to lowering the polymer concentration. This favorable synergy will reduce chemical-consumption costs and improve recovery to enhance EOR-project economics.

Conformation and dynamics of flexible polyelectrolytes in semidilute salt-free solutions.

We present steady shear rheology data for sodium polystyrene sulfonate (NaPSS) in semidilute unentangled salt-free aqueous solution as a function of polymer concentration (c) and degree of polymerisation (N). The measured terminal modulus (G) agrees with the scaling prediction of G ≃ kBTc/N. The specific viscosity varies with the degree of polymerisation as ηsp ∝ N1.24±0.08. The observed dependence differs with the linear relation expected from the Rouse model for ideal chains as predicted by de Gennes' scaling model and subsequent theories. Together with the diffusion data of Oostwal et al., our results suggest that chains may follow non-Gaussian statistics beyond the correlation length (ξ). Small angle neutron scattering data on salt-free semidilute solutions at low polymer concentrations partially support this hypothesis but do not confirm it. The electrostatic Kuhn length of NaPSS salt-free solutions is found to be proportional and slightly larger than the correlation length (LK,e ≃ 1.3ξ). This result agrees well with the scaling model of Dobrynin et al. Radii of gyration (Rg) data as a function of polymer concentration reveal that a concentrated regime (Rg ∝ c0) does not occur for NaPSS in the concentration range considered (c ≲ 4M). We conclude by comparing the predictions of the scaling model of Dobrynin et al. and Muthukumar's double screening theory with viscosity data for different polyelectrolyte-solvent systems. Dobrynin's model provides a better description of experimental observations. Our findings confirm several aspects of current models for polyelectrolyte solutions but some deviations from theory remain.