Bulk Solution Viscosity Research Articles

Experimental investigation of amine-surfactant CO2 foam for smart mobility control during CO2 flooding

Amine-surfactant can be converted to be cationic surfactant in water solution saturated with CO2, which can enhance their foaming ability and foam stability, and the foaming ability can be switched off or on by CO2 or replacing with N2 with heating, so the amine-surfactants have great potential for smart mobility control to gas channeling during CO2 flooding. In this study, three alkyl propyl dimethylamines with different carbon chain length (R = 11, 17 and 22, named as UC11AMPM, UC17AMPM, and UC22AMPM, respectively), were investigated as CO2 responsive foam agent, and their foam performance under static and dynamic condition was tested up to 130 °C and 10.5 MPa using a visualized foam meter and a sand-pack flooding setup. The influence of carbon chain length on bulk solution viscosity, surface activity, foaming ability, and foam quality on bulk foam stability were measured and analyzed. The experimental results indicate that the three amine surfactants all demonstrate well CO2 responsibility and CO2 foaming ability, and show well switchable by CO2 and N2 at high temperature and high pressure (HTHP) condition. With the carbon chain length increasing, the surfactant shows higher absorption on the foam films, and bulk solution has a higher viscosity, which can decrease de-foam velocity and enhance the foam stability, as a result, the surfactant shows higher mobility control ability.

Relationship between Structure, Functionality, and Viscosity for Aerosol-Mimicking Solutions Containing Ammonium Sulfate, Glyoxal, and a Series of Oxidized C1–C5 Compounds

The physical properties of aqueous secondary organic aerosol (SOA) can be influenced by the chemical composition of the solvent matrix within which SOA-forming reactions take place. The chemical structure and functionality of perturbing solutes on solution viscosity in bulk-phase SOA-modeling reaction mixtures containing glyoxal and ammonium sulfate were measured for a series of oxidized C1–C5 compounds. In general, as the solute concentration increased, solution viscosity increased, with the magnitude of those increases dependent upon the solute species added. The presence of glyoxal increased viscosity in about 50% of mixtures as a result of specific solute/solvent/product interactions. The oxygen/carbon (O/C) ratio was found to have a linear relationship with relative viscosity at a high solute concentration such that every −CH2CH2OH moiety addition increased solution viscosity by 25%. Solutes with identical O/C ratios but different structural characteristics (for example, acetone, 1-propanol, and 2-propanol) showed 7–8% differences in viscosity as a function of the chain length or ability to act as a hydrogen bond donor. The addition of an alcohol group increased viscosity by 10–20% over hydrogen or methyl groups in the same position. The solute structure appears to play a role in mediating intrasolvent interactions, and increases in hydrogen bonding and intersolute interactions lead to increased bulk solution viscosity, as shown in a series of experiments varying the timing and order of solute addition. These solutes are models for oxidized aerosol components, and the structure-dependent results suggest the importance of the aqueous layer functional group presence on aerosol physical properties, such as viscosity.

Probing the molecular design of hyper-branched aryl polyesters towards lubricant applications.

We report novel polymeric materials that may be used as viscosity index improvers (VII) for lubricant applications. Our efforts included probing the comb-burst hyper-branched aryl polyester architecture for beneficial viscosity and friction behavior when utilized as an additive in a group I oil. The monomer was designed as to undergo polymerization via polycondensation within the architectural construct (AB2), typical of hyperbranched polymers. The monomer design was comprised of aliphatic arms (12 or 16 methylenes) to provide the necessary lipophilicity to achieve solubility in a non-polar medium. Once polymerized, via catalyst and heat, the surface alcohols were functionalized with fatty acids (lauric and palmitic). Controlling the aliphatic nature of the internal arms and peripheral end-groups provided four unique flexible polymer designs. Changing the reaction time and concentration provided opportunities to investigate the influence of molecular weight and branching density on oil-solubility, viscosity, and friction. Oil-solubility was found to decrease with fewer internal carbons, but the number of internal carbons appears to have little influence on the bulk solution viscosity. At concentrations of 2 wt % in a group I base oil, these polymer additives demonstrated an improved viscosity index and reduced friction coefficient, validating the basic approach.

Self-Consistent Colloidal Energy and Diffusivity Landscapes in Macromolecular Solutions

We report a dynamic analysis to simultaneously measure colloidal forces and hydrodynamic interactions in the presence of both adsorbed and unadsorbed macromolecules. A Bayesian inference method is used to self-consistently obtain the position-dependent potential energy (i.e., energy landscape) and diffusivity (i.e., diffusivity landscape) from measured colloidal trajectories normal to a wall. Measurements are performed for particles and surfaces with adsorbed polyethylene oxide (PEO) copolymer as a function of unadsorbed PEO homopolymer concentration. Energy landscapes are well described by a steric repulsion between adsorbed brushes and depletion attraction due to unadsorbed macromolecules. Diffusivity landscapes show agreement with predicted short-range permeable brush models and long-range mobilities determined by the bulk solution viscosity. Lower than expected mobilities in the vicinity of overlapping depletion layers are attributed to interactions of adsorbed and unadsorbed macromolecules altering nonconservative lubrication forces.

Measurements of the timescales for the mass transfer of water in glassy aerosol at low relative humidity and ambient temperature

Abstract. The influence of glassy states and highly viscous solution phases on the timescale of aerosol particle equilibration with water vapour is examined. In particular, the kinetics of mass transfer of water between the condensed and gas phases has been studied for sucrose solution droplets under conditions above and below the glass transition relative humidity (RH). Above the glass transition, sucrose droplets are shown to equilibrate on a timescale comparable to the change in RH. Below the glass transition, the timescale for mass transfer is shown to be extremely slow, with particles remaining in a state of disequilibrium even after timescales of more than 10 000 s. A phenomenological approach for quantifying the time response of particle size is used to illustrate the influence of the glassy aerosol state on the kinetics of mass transfer of water: the time is estimated for the droplet to reach the halfway point from an initial state towards a disequilibrium state at which the rate of size change decreases below 1 nm every 10 000 s. This half-time increases above 1000 s once the particle can be assumed to have formed a glass. The measurements are shown to be consistent with kinetic simulations of the slow diffusion of water within the particle bulk. When increasing the RH from below to above the glass transition, a particle can return to equilibrium with the gas phase on a timescale of 10's to 100's of seconds, once again forming a solution droplet. This is considerably shorter than the timescale for the size change of the particle when glassy and suggests that the dissolution of the glassy core can proceed rapidly, at least at room temperature. Similar behaviour in the slowing of the mass transfer rate below the glass transition RH is observed for binary aqueous raffinose solution droplets. Mixed component droplets of sucrose/sodium chloride/water also show slow equilibration at low RH, illustrating the importance of understanding the role of the bulk solution viscosity on the rate of mass transfer with the gas phase, even under conditions that may not lead to the formation of a glass.

Application of PET deprotection for orthogonal photocontrol of aqueous solution viscosity

Photorelease and photoisomerization of trans-cinnamic acid in aqueous CTAB solutions induces a bulk solution viscosity increase and decrease, respectively, triggered by orthogonal irradiation wavelengths.

Viscosity-Dependent Protein Dynamics

Spectrally resolved stimulated vibrational echo spectroscopy is used to investigate the dependence of fast protein dynamics on bulk solution viscosity at room temperature in four heme proteins: hemoglobin, myoglobin, a myoglobin mutant with the distal histidine replaced by a valine (H64V), and a cytochrome c 552 mutant with the distal methionine replaced by an alanine (M61A). Fructose is added to increase the viscosity of the aqueous protein solutions over many orders of magnitude. The fast dynamics of the four globular proteins were found to be sensitive to solution viscosity and asymptotically approached the dynamical behavior that was previously observed in room temperature sugar glasses. The viscosity-dependent protein dynamics are analyzed in the context of a viscoelastic relaxation model that treats the protein as a deformable breathing sphere. The viscoelastic model is in qualitative agreement with the experimental data but does not capture sufficient system detail to offer a quantitative description of the underlying fluctuation amplitudes and relaxation rates. A calibration method based on the near-infrared spectrum of water overtones was constructed to accurately determine the viscosity of small volumes of protein solutions.

Variegated micelle surfaces: correlating the microstructure of mixed surfactant micelles with bulk solution properties.

Electron paramagnetic resonance, viscosity, and small-angle neutron scattering (SANS) measurements have been used to study the interaction of mixed anionic/nonionic surfactant micelles with the polyampholytic protein gelatin. Sodium dodecyl sulfate (SDS) and the nonionic surfactant dodecylmalono-bis-N-methylglucamide (C12BNMG) were chosen as "interacting" and "noninteracting" surfactants, respectively; SDS micelles bind strongly to gelatin but C12BNMG micelles do not. Further, the two surfactants interact synergistically in the absence of the gelatin. The effects of total surfactant concentration and surfactant mole fraction have been investigated. Previous work (Griffiths et al. Langmuir 2000, 16 (26), 9983-9990) has shown that above a critical solution mole fraction, mixed micelles bind to gelatin. This critical mole fraction corresponds to a micelle surface that has no displaceable water (Griffiths et al. J. Phys. Chem. B 2001, 105 (31), 7465). On binding of the mixed micelle, the bulk solution viscosity increases, with the viscosity-surfactant concentration behavior being strongly dependent on the solution surfactant mole fraction. The viscosity at a stoichiometry of approximately one micelle per gelatin molecule observed in SDS-rich mixtures scales with the surface area of the micelle occupied by the interacting surfactant, SDS. Below the critical solution mole fraction, there is no significant increase in viscosity with increasing surfactant concentration. Further, the SANS behavior of the gelatin/mixed surfactant systems below the critical micelle mole fraction can be described as a simple summation of those arising from the separate gelatin and binary mixed surfactant micelles. By contrast, for systems above the critical micelle mole fraction, the SANS data cannot be described by such a simple approach. No signature from any unperturbed gelatin could be detected in the gelatin/mixed surfactant system. The gelatin scattering is very similar in form to the surfactant scattering, confirming the widely accepted picture that the polymer "wraps" around the micelle surface. The gelatin scattering in the presence of deuterated surfactants is insensitive to the micelle composition provided the composition is above the critical value, suggesting that the viscosity enhancement observed arises from the number and strength of the micelle-polymer contact points rather than the gelatin conformation per se.

Two-photon fluorescence-guided laser tweezers for study of cluster growth and gelation process

Laser tweezers trapping technology has been used to monitor the bulk solution viscosity during the sol-gel gelation process at different depths from an interface. The gelation rate is the same in depth ranges 2–20 μm from the bounding surface. Simultaneously with the laser tweezers study, a microviscosity kinetic measurement of the sol-gel process was performed by fluorescent anisotropy and quantum yield methods. The large differences found between the bulk and microviscosities obtained in the experiment reflect the intrinsic differences in solution environment sensed by the laser tweezers on the macro level and by other optical techniques on the microlevels.

Polyacrylamide Adsorption from Aqueous Solutions on Gold and Silver Surfaces Monitored by the Quartz Crystal Microbalance

Viscoelastic properties of ultrathin films are important in such applications as polymer-supported lipid bilayers, and the quartz crystal microbalance (QCM) offers the ability to measure these properties in situ. In this study, polymer films are created by adsorbing polyacrylamide to gold and silver surfaces from aqueous solutions. The molecular weight of the polymers ranges from 10 000 to 1 000 000 g/mol, and concentrations range from dilute to the overlap concentration. Using a continuum mechanics viscoelastic film model, we extract film property parameters from frequency and dissipation change measurements for multiple harmonics. The precision of the QCM and the modeling technique are limited, however, leading to large property value ranges for any given film. The adsorbed films range from 10 to 150 Å thick, with moduli ranging from 15 to 228 kPa and viscosities ranging from 1.21 × 10-3 to 2.85 × 10-3 Pa s. Meanwhile, the bulk solution properties of the different molecular weight materials lead to drastically different adsorption profiles. While the viscosity differences between water and 10 000 Mw polymer solutions lead to large frequency and dissipation responses, the large relaxation times of 1 000 000 Mw polymers make their bulk solution viscosity differences from water largely undetectable by the QCM. In addition, the viscosity of the 10 000 Mw solutions may be frequency dependent over the range of operating frequencies, contrary to the standard QCM assumption of frequency independence.

Dynamic flavor release from sucrose solutions.

The initial dynamic flavor release from sucrose solutions was modeled. Modeling was based on the theoretical hydration behavior of sucrose, theoretical physicochemical data of flavor volatiles, and process parameters of a headspace apparatus used for model validation. The rate-limiting factor determining the initial flavor release was the hydration of sucrose, which in turn depends on the molarity of sucrose in the solution and, therefore, on the actual amount of nonbound water. Improved solubility of the more hydrophilic compounds due to their orientation toward the hydration shells of the sugar molecules was considered. The viscosity of nonassociated water forming the microregion for mass transfer of volatiles was considered instead of the bulk solution viscosity. Experimental validation of the model by real-time measurements of dynamic flavor release using foodlike flavor concentrations confirmed the above theory. Increasing sucrose concentrations resulted predominantly in increased flavor release, and bulk solution viscosity showed no effect.

Solvation and rotational dynamics in acetonitrile/propylene carbonate mixtures: a binary system for use in dynamical solvent effect studies

Equilibrium and nonequilibrium solvation properties as measured by the Stokes shift of coumarin 153 are reported for a series of acetonitrile/propylene carbonate binary mixtures at room temperature. Steady-state spectroscopy shows that the solvent reorganization energy is independent of composition in this mixture. Solvation and rotational times vary nearly ten-fold between the pure solvent limits, in a manner that is correlated to bulk solution viscosity. The wide range of solvation times together with the constant solvent reorganization energy should render this binary system useful for investigating dynamical solvent effects on charge-transfer processes.

Probing the Microscopic Molecular Environment in Liquids: Intermolecular Dynamics of CS2 in Alkane Solvents

The femtosecond optical-heterodyne-detected optical Kerr effect/Raman-induced Kerr effect (OHD OKE/RIKE) dynamics of CS2 dissolved in a series of alkane solvents are reported. The data reveal that the nondiffusive (subpicosecond) dynamics of simple molecular liquids are determined largely by the details of the local, microscopic environment, rather than by the bulk solution properties, with no correlation observed between the short-time, nondiffusive dynamics and the bulk solution viscosity. For each solvent investigated, the vibrational spectral density is observed to narrow and shift to lower frequency with increasing dilution. While the same general trend is observed for each solvent, deviations of magnitude are observed for the longer-chain n-alkanes. This, coupled with the markedly nonexponential decay of the orientational anisotropy observed for the higher-alkane dilutions, suggests the presence of two distinct environments in which isolated pockets of CS2 exist. The observed spectral evolution is d...

Diffusion of Spheres in Entangled Polymer Solutions: A Return to Stokes-Einstein Behavior

Dynamic light scattering has been used to follow the tracer diffusion of polystyrene spheres (R200 nm) in dilute, semidilute, and entangled solutions of poly(vinyl methyl ether) (M w = 1.3×10 6 ). Over this range of matrix concentrations, 0 ≤ c[η] ≤ 36, the diffusivity drops by almost 5 orders of magnitude. Near c * (∼ [η] -1 ) for the matrix, the diffusivity exceeds that estimated from the bulk solution viscosity via the Stokes-Einstein relation by a factor of about 3. Such expositive deviations« from Stokes-Einstein behavior have been reported previously in several systems. However, once the matrix concentration is sufficiently high for entanglements to be effective, Stokes-Einstein behavior is recovered

Electrokinetic parameters for capillaries of different geometries

The electrokinetic parameters describing electroosmosis, ion conduction, and streaming potential were computed for long capillaries of three different shapes: circle, ellipse, and infinite slit. The nonlinear Poisson-Boltzmann equation was numerically solved to obtain electrical potential profiles within the pores, which were integrated into the classical momentum and conduction equations. Because an electrolyte which is symmetric in both charge and mobility was assumed, the results for each pore geometry could be expressed in terms of two parameters, a dimensionless wall charge and radius. The calculations show that pore shape is sometimes an important factor, but the results for a circle can be corrected by a surface-to-volume ratio to obtain the correct parameters for an ellipse. Calculations of the electroviscous effect for water-filled circular capillaries show that its maximum augmentation is 28% of the bulk solution viscosity.

Hydrophobic nitroxide radicals as probes to investigate the hydrophobic interaction

The EPR spectrum of 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO) has been systematically investigated in several solvents and in aqueous solutions of glycerol,t-BuOH, Bu4NBr,n-HexNH3Br,n-OctNH3Br, NaBPh4, and Ph4AsCl. Most of the results have been obtained at 25°C, though the temperature dependence of the linewidths has been examined in water and several organic solvents. Data on the spectrum of ditertiarybutylnitroxide in aqueous solutions of glycerol and Bu4NBr are also presented. The spectrum was simulated to determine WH, the linewidth after allowance for the unresolved proton hyperfine interaction, in each manifold of the triplet due to the nitrogen hyperfine interaction. The linewidth WH is analyzed in terms of the reorientational correlation time Aθ and the angular velocity correlation time AJ. In most solutions Aθ is determined only by the bulk solution viscosity, except in situations where significant clustering of hydrophobic solute molecules occurs. In pure nonaqueous solvents the temperature dependence results are consistent with AJ being determined by the bulk viscosity, while in water or aqueous solutions, a very different behavior is found which is interpreted as a manifestation of clathrate-like hydration of the hydrophobic radical. This interpretation is incorporated in a two-state model developed to account for the WH data of TEMPO in aqueous solutions of various hydrophobic solutes. The equilibrium parameters derived from the model, for the association of TEMPO with several hydrophobic solutes, support the concept of hydrophobic interactions as pictured from thermodynamic excess functions.

The influence of solution viscosity on the dissolution rate of soluble salts, and the measurement of an "effective" viscosity.

Abstract The rate of solution of KCl and NaCl from compressed discs has been determined under controlled conditions, in water at 25° and in solutions of varying concentrations of polyvinylpyrrolidone (molecular weight 360 000), polyoxyethylene glycol 6000 and cetomacrogol 1000. Dissolution rate constants decrease with increasing bulk solution viscosity, as expected, but no one equation relating rate constant and bulk viscosity fits the results for the systems studied. Calculation of an effective viscosity from the diffusion coefficients of the salts in water and the diffusion coefficients of the salt in the polymer solutions enables an empirical correlation of the results to be made. The relation of the effective viscosity to the microscopic viscosity is discussed in an Appendix.

Coalescence of liquid drops at oil-water interfaces

Measurements were made of the length of time single drops can exist at an oil-water interface before coalescence takes place with a bulk phase of the same composition as the drop. The effect of stabilizing agents soluble in either the oil or water phases was investigated. Factors investigated included: ( 1) temperature; ( 2) size of drops and curvature of O-W interfaces; ( 3) O/W vs. W/O drops; ( 4) kind of oil; ( 5) mutual solubility of oil and water phases; ( 6) type of stabilizing agent, its concentration, pH, interfacial viscosity, and rigidity. The stability of drops decreases as the temperature is raised; the temperature dependence depends upon both the type of oil and the stabilizing agent. Oil drops are generally more stable than water drops when the stabilizing agent is water-soluble; the opposite is true for oil-soluble stabilizers. Oil-water phases which are mutually saturated with each other form more stable drops than unsaturated systems. The lifetime of drops depends roughly upon the cube root of the concentration of stabilizing agent in general. Stabilizers which produce a large viscosity or rigidity at the O-W interface also give stable drops; however, some good stabilizers show no interfacial viscosity or rigidity. Polyelectrolytes such as polymethacrylic acid and carboxymethyl cellulose stabilize drops better as acids than as salts; this behavior correlates with the interfacial viscosity behavior but not with the bulk solution viscosity. Simple mechanical models of drop coalescence can explain only some of the observed results. Many of the data may be understood in terms of the generalizations: ( 1) any factor which disturbs the O-W interface on a molecular scale decreases the stability of drops; ( 2) many stabilizers are most effective when they are on the verge of precipitation.