Rheological properties of wormlike micelles formed in the sodium oleate/trisodium phosphate aqueous solution

Aqueous solution of anionic surfactant,sodium oleate（NaOA）,was studied by means of steady-state shear rheology and dynamic oscillatory technique.The system of NaOA/Na3PO4 showed high viscosity,strong viscoelasticity and good ability of countering Ca^2＋,Mg^2＋.The Maxwell model and Cole-Cole plot were applied to study the dynamic viscoelasticity of wormlike micelles.The microstructures of the wormlike micelles were characterized by FF-TEM.

Compressed wormlike chain moving out of confined space: A model of DNA ejection from bacteriophage

The molecular biomechanics of DNA ejection from bacteriophage is of interest to not only fundamental biological understandings but also practical applications such as the design of advanced site-specific and controllable drug delivery systems. In this paper, we analyze the viscous motion of a semiflexible polymer chain coming out of a strongly confined space as a model to investigate the effects of various structure confinements and frictional resistances encountered during the DNA ejection process. The theoretically predicted relations between the ejection speed, ejection time, ejection length, and other physical parameters, such as the phage type, total genome length and ionic state of external buffer solutions, show excellent agreement with in vitro experimental observations in the literature.

Visualization of Wormlike Micelle Fluid Flow in a Mixing Tank

In this study,particle image velocimetry was applied to investigate flow fields of wormlike micelle(WLM) fluids in a mixing tank equipped with a four-blade,down-pumping,pitched blade turbine. First,the rheology of WLM fluids was investigated,and the Carreau model was utilized to describe their apparent viscosity. Then,the effects of the rotation speeds and rheological properties on the flow fields were studied using different WLM fluids at different rotation speeds. The results revealed that with increasing Reynolds number,the discharge angle decreases and the carven size increases. Furthermore,elastic effects of WLM fluids lead to a more curved flow and a smaller carven.

Molecular origin for pH-responsive wormlike micelles of zwitterionic surfactants triggered by aromatic acid derivatives

Introduction of aromatic acid derivatives(AADs)into zwitterionic surfactants is an efficient method to prepare wormlike micelles with pH-controllable viscosity;however,the coincident molecular origin of AAD/zwitterionic surfactant binary mixtures remains unclear.Herein,the self-assembly of hydroxyl derivatives of benzoic acid(BA)and cetyldimethyl betaine(BS-16)mixtures in water was systematically assessed,and various factors,such as the molecular structure,molar ratio of AAD and BS-16,and solution pH,were investigated.The structure-property relationship of AAD/BS-16 binary mixtures was established,which provided the molecular origin for the effect of AAD on micellar microstructures and the pH-induced morphological transitions.The ortho-substituted hydroxyl moiety in the BA molecule facilitated the formation of larger wormlike micelles,whereas the effect of the meta-substituted moiety was less significant.The para-substituted hydroxyl moiety in BA did not favor micellar growth.This moiety exhibited similar characteristics to the increasing hydroxyl moiety number in the AAD molecules or solution pH where the negative effects of steric hindrance and electrostatic interactions of molecules in micelles aredominant.

Wormlike Micelle Formation and Rheological Behavior in the Aqueous Solutions of Mixed Sulfate Gemini Surfactant without Spacer Group and Dodecyltrimethylammonium Bromide

The rheological behavior of the aqueous solutions of mixed sulfate gemini surfactant with no spacer group, referred to as d-C12S, and dodecyltrimethylammonium bromide （C12TABr） at a total concentration of 100 mmol,L-1 but different molar ratios of ClzTABr to d-C12S （a1） was investigated using steady rate and frequency sweep measurements. The wormlike micelles were formed over a narrow a1 range of 0.20-0.27. The viscoelastic solutions exhibited Maxwell fluid behavior. At the optimum molar ratio of 0.25, the zero-shear viscosity was as high as 600 paos and the length of the mixed wormlike micelle was about 0.45-0.85 pm. The present result provides an exam- ple to construct long wormlike micelles by anionic gemini surfactant.

Formation of wormlike mi-celles in anionic surfactant AES aqueous solutions

The growth and structure of anionic micelles of sodium dodecyl trioxyethylene sulfate (AES) in the presence of multivalent counterion Al3+ were investigated by means of dynamic rheological methods. It has been obtained by themeasurements of shear viscosity, complex viscosity anddynamic moduli, as well as the application of Cox-Merz rule and Cole-Cole plot that wormlike micelle and networkstructure could be formed in AES/AlCl3 aqueous solutions. The structure was of a character of nonlinear viscoelasticfluid and departure from the simple Maxwell model. Thetechnique of freeze-fracture transmission electronmicroscopy (FF-TEM) was also used to confirm theformation of this interesting structure.

Numerical Simulation of the Distribution Function and Free Energy of a Single Wormlike Polymer Confined between Hard Walls

We focus on the distribution and free energy of a wormlike polymer confined between two parallel hard walls.The variation in the distribution and free energy of the wormlike chain as the spacing between the walls decreases(or as the total contour length of the wormlike chain increases or as the persistence length of the chain increases)is simulated.The main reason for these changes is a degradation of the long wormlike chain into a Gaussian long chain under weak confinement.

A robust viscoelastic surfactant tolerating 20% HCl up to 150℃ for oil well stimulation

Viscoelastic surfactants(VES)are often used as viscous diverters in acidizing stimulation to prolong the acid consumption time and maximize zonal coverage of the acid for improving well productivity.However,the ceiling temperature of commercial VES cannot exceed 120℃in practical use because of the poor thermal stability and fragile molecular structure,hindering their implementation in hightemperature oil reservoirs,i.e.,≥150℃.Here we synthesized a novel C22-tailed diamine,N-erucaminopropyl-N,N-dimethylamine(EDPA),and examined comparatively its rheological behavior,assemblies morphology and molecular stability in 20 wt%HCl with a commercial VES,erucyl dimethyl amidopropyl betaine(EDAB).The feasibility of EDPA for acidizing stimulation was assessed by acid etching of carbonate rock with its HCl solution at 150℃.Rheological results showed that the 2.5 wt%EDPA—20 wt%HCl solution maintains stable viscosity of 90 m Pa s at 150℃for 60 min,while that of 2.0 wt%EDAB HCl solution is just 1 m Pa s under identical conditions.1H NMR spectra and cryo-TEM observations revealed that the chemical structure and self-assembled architectures of EDPA remained intact in such context,but the EDAB suffered from degradation due to the hydrolysis of the amide group,accounting for the poor heat-resistance and acid-tolerance.The reaction rate of 2.5 wt%EDPA HCl solution with carbonate rock was one order of magnitude lower than that of 20 wt%HCl solution at 150℃,underpinning the potential of EDPA to be used in the high-temperature reservoirs acidizing.This work improved the thermal tolerance of VES in highly concentrated HCl solution,paving a feasible way for the acidization of high-temperature reservoir environments(~150℃).

Preparation of a kind of mesoporous carbon and its performance in adsorptive desulfurization

Carbon materials were prepared using mesoporous silica HMS with different pore sizes as the hard templates and water-soluble phenolic resin as the carbon source. The obtained materials were characterized by powder X-ray diffraction, transmission electron microscopy and N2 physical adsorption, and were used in adsorptive desulfurization. It has been shown that the carbon material prepared using HMS with larger pore size （〉3 nm） presented uniform wormlike mesopore of 2.3 nm and large BET surface area （1903 m2/g）. The mesoporous carbon was an excellent adsorbent to remove the refractory sulfur compound in diesel, especially dibenzothiophene and 4, 6-dimethyldibenzothiophene.

New type flooding systems in enhanced oil recovery

Wormlike micelles, obtained in anionic surfactam sodium oleate （NaOA） solutions in the presence of sodium phosphate （Na3PO4）, were studied using the steady and dynamic rheological methods. The laboratory simulation flooding experiments were used to investigate the effects of flooding for the wormlike micelles system. The results show that the oil recovery is 32.7%. This flooding system is a new type and has high activity with a low cost.

A systematic rheological study of alkyl amine surfactants for fluid mobility control in hydrocarbon reservoirs

The basis of this study is to identify the versatility of N,N,N＇-trimethyl-N＇-tallow-1,3-diaminopropane（DTTM） surfactant in high saline environments. The surfactant was examined with sodium chloride, NaCl, to understand how triggers such as salt, p H, temperature, and surfactant concentration influences the viscoelastic response of the surfactant solution. The DTTM surfactant and salt（NaCl） concentrations used in steady-state shear viscosity analysis range from 0.2 wt% to 2 wt%and 5 wt% to 25 wt%, respectively. Along with DTTM results, three similar chemical structures are investigated to understand how viscosity changes with alterations in tail and head group composition. It was found that DTTM surfactant has the capability of transitioning from a foam-bearing to viscoelastic state at low surfactant concentrations under moderate to high saline conditions. A longer tail length promotes viscoelasticity and shear-thinning behavior. Terminals consisting of hydroxides or ethoxylates have a lower viscosity than that of methyl terminals. A head group consisting of two nitrogen atoms has a higher viscosity than those containing one nitrogen atom. The rheological characterization of DTTM presented in this paper is part of a larger study in determining the capability of this surfactant to foam CO2 for improving mobility control in CO2 enhanced oil recovery in high saline oil formations.

Chain Conformation and Local Rigidity of Soluble Polyimides(II):Isomerized Polyimides in THF

Two soluble isomerized polyimides（PIs） synthesized from 2,2＇-bis（3,4-dicarboxyphenyl）hexafluoropropane dianhydride（6FDA） with either 2,2＇-dimethylbenzidine（2,2＇-DMB） or 3,3＇-DMB were investigated by means of size-exclusion chromatography coupled with multi-angle laser light scattering,a viscometer and a refractive index detector in tetrahydrofuran（THF） with tetrabutylammonium bromide（TBAB） at 35 ℃.The corresponding parameters related to conformations α and ν,evaluated from the scaling relationships [η]=K η M α and R g =K g M ν,respectively,were 0.66±0.01 and 0.55±0.02 for poly（6FDA/3,3＇-DMB）,and 0.67±0.01 and 0.56±0.01 for poly（6FDA/2,2＇-DMB）,indicating a random coil conformation for both the samples in this mobile system.The persistence length l p and shift factor M L（relative molecular weight per unit contour length） were estimated from the relationship between intrinsic viscosity and molecular weight for the wormlike cylinder model proposed by Bohdanecky.Both l p and M L showed that the two PIs in THF are flexible chains and exhibit some local rigidity to some extent.

刚柔高分子体系自组装对称胶束的自洽场模拟

嵌段共聚物和均聚物的混合体系在不同条件下能够自组装形成丰富的微观结构.基于wormlike链模型,给出巨正则系综下刚柔两嵌段共聚物和相应的柔性均聚物(rod-coil/coil)混合体系的自洽场理论,并将相应的自洽场算法运用于刚柔混合体系下临界胶束结构的数值模拟,得到与coil-coil体系下自组装临界胶束类似的结构和性质,即会形成不同的胶束结构,且随着嵌段A的体积分数的增加,胶束的稳定形态从平面相转化为柱状相再到球状相的性质,在径向方向上序参量的变化也表明胶束结构的转变过程。

Stretching strongly confined semiflexible polymer chain

By the so-called wormlike chain （WLC） model in polymer physics envision- ing an isotropic rod that is continuously flexible, the force-extension relations of semi- flexible polymer chains strongly constrained by various confinements are theoretically investigated, including a slab-like confinement where the polymer chains are sandwiched between two parallel impenetrable walls, and a capped nanochannel confinement with a circular or rectangular cross-section where the chains are bounded in three directions. The Brownian dynamics （BD） simulations based on the generalized bead-rod （GBR） model are performed to verify the theoretical predictions.

Synergistic Effect of Cocamidopropyl Betaine and Sodium Lauroyl Sarcosinate

In this study,we investigated the synergistic effect of a zwitterionic surfactant(cocamidopropyl betaine)and amino acid surfactant(sodium lauroyl sarcosinate)by measurements of surface tension,rheological properties,dynamic light scattering(DLS),and transmission electron microscopy(TEM).The results confirm the formation of wormlike micelles in the mixed system,which leads to superior surface activity as compared to that of an individual surfactant.Stable and dynamic viscoelastic measurements were also performed to explore the characteristics of wormlike micelles at different mole fractions,p H values,and temperatures.The results indicate that the strongest wormlike structure formed under the conditions of X_(1)=0.5,pH=4.7,and C T=600 mmol/L.The size and morphology of the mixed micelles were obtained by DLS and TEM.The results of this work offer insight into the interaction between zwitterionic and amino acid surfactants,which will contribute to the design of complex surfactants.

Temperature Dependence of Chain Conformation and Local Rigidity of Isomerized Polyimides in Dimethyl Formamide

Temperature dependence of chain conformation and local rigidity of two soluble isomerized polyimides （PIs）, poly（hexafluorodianhydride/3,3＇-dimethylbenzidine）[poly（6FDA/3,3＇-DMB）] and poly（hexafluorodianhy- dride/2,2＇-dimethylbenzidine）[poly（6FDA/2,2＇-DMB）] were investigated by dilute solution viscosity, size exclusion chromatography（SEC） coupled with multi-angle laser light scattering, viscometer, and refractive index detector in dimethylformamide（DMF） with either 0.1 mol/L LiBr or 3.1 mmol/L tetrabutylammonium bromide（TBAB） in the temperature range of 30 to 50 ~C. The scaling relationships of [t/]=K^M~ and Rg=KgMv obtained are employed to in- vestigate the temperature dependence of chain conformation for the two polyimides. The values of a and v are in the range of 0.66--0.69 and 0.53--0.56, respectively, for poly（6FDA/3,3＇-DMB）, meanwhile they are in the range of 0.64--0.68 and 0.53--0.56, respectively, for poly（6FDAJ2,2＇-DMB）. These results reveal that random coil conforma- tions for both Pls are not affected visibly with increasing temperature from 30 ~C to 50 ~C. However, values of more exact intrinsic viscosity from dilute solution measurement indicate there is only tiny coil extension or shrinkage for both PIs with temperature rising. Parameters related to chain flexibility of polymer, including persistence length lp, shift factor ME（relative molecular weight per unit contour length） and backbone diameter d are estimated from the relationship between intrinsic viscosity and molecular weight for the continuous wormlike cylinder model, which indicates that two samples are flexible chains, only the chain of poly（6FDA/3,3＇-DMB） is stiffer than that of poly（6FDA/2,2＇-DMB） slightly.

Rheological study of nanoparticle-based cationic surfactant solutions

Worm-like micelles are of special interest among the many forms of surfactant aggregates because of their usefulness in research and technology.Micelles are elongated,flexible aggregates formed by amphiphilic molecules spontaneously self-organizing in liquids.The nature of the surfactant determines its unique shape,which may be altered by mixing it with other substances or changing physicochemical variables like as temperature,pH,or salinity.The rheology of viscoelastic fluid systems is currently being modified using nanoparticles.This method,which was just introduced about 10 years ago,has shown to be highly promising,producing significant improvements in rheological properties,particularly at reservoir temperatures.The goal of this research is to investigate and assess the rheology of an aqueous cationic surfactant solution based on graphene oxide nanoparticles.The thermodynamics,structure and rheology of nanoparticle-based cationic surfactant solutions were investigated experimentally.According to structural and thermodynamic investigations in surfactant-nanoparticle mixtures,micellenanoparticle interactions arise as physical crosslinks between micelles.The existence of these interactions is shown to generate considerable viscosity and viscoelasticity in wormlike micelles,even when the fluid is Newtonian in the absence of nanoparticles.The viscosity,shear modulus and relaxation time all increase as particle concentration increases.Adding nanoparticles generates a network of micellar entanglements as a result of that.Our results demonstrate that adding nanoparticles to surfactant solutions provides for a one-of-a-kind method of altering fluid rheology under a range of circumstances.

Metal-ligand coordinated Ca(DS)_2/C_(14)DMAO/H_2O system:Phase behavior and rheological property

A metal-ligand coordinated surfactant system formed by calcium dodecylsulfate(Ca(DS)2)/tetradecyldimethylamine oxide (C14DMAO)/H2O was studied in terms of surface tension,conductivity,negative-staining TEM,phase behavior and rheological operation.In C14DMAO solution,when Ca(DS)2 is added,metal-ligand complexes form between the Ca 2+and N→O group of C14DMAO.Under this metal-ligand driving force,different phases can be obtained at different concentrations and different ratios of Ca(DS)2 and C14DMAO.At the fixed C14DMAO concentration,L1-phase consisting of spherical micelles forms at first.With the addition of Ca(DS)2,the spherical micelles elongate to be wormlike micelles and then after an L1/L-two phase region,the birefringent vesicle-phase(Lv-phase)region is observed.When Ca(DS)2 concentration continues to increase,a gel-phase region is found after the Lv-phase region and then precipitates of undissolved Ca(DS)2 appear.The transition between different phases is affected by temperature remarkably.The wormlike micellar solutions and vesicle solutions were checked by rheological measurements and showed apparent viscoelasticity at high surfactant concentrations.

Rheological behavior of mixed system of ionic liquid [C8mim]Br and sodium oleate in water

Abstract We report on the rheological behavior of wormlike micelles constructed by ionic liquid surfactant [Csmim]Br （1-octyl-3-methylimidazolium bromide） and anionic surfactant sodium oleate （NaOA） in aqueous solution. The effects of surfactant composition, total surfactant concentration, added salts, and temperature were investigated. The prevailing surfactant effect at lower concentration and the leading cosolvent effect at higher concentration of [Csmim]Br may be the main reasons for appearance of well-established maximum in key rheologi- cal parameters with variation of surfactant composition and total surfactant concentration. The Cole-Cole plots demon- strate that the systems （total surfactant concentration falls within 0.17-0.35 mol. L- 1 and molar ratio 0.33≤R ≤ 0.50） fit the Maxwell＇s mechanical model as linear viscoelastic fluid. The addition of NaBr or sodium salicylate decreases significantly the viscosity and the relaxation time of the wormlike micelle solution but cannot change the value of plateau modulus Go. The present system has low rheological tolerance to temperature. The increase of temperature decreases the average contour length and viscosity of wormlike micelles and thus strengthens the relaxation progress of diffusion and weakens the relaxation progress of reptation. Increasing the temperature also decreases the value of plateau modulus G0 and shifts the minimum value of the loss modulus G″min to higher frequencies.