Rheological properties of wormlike micelles in sodium oleate solution induced by sodium ion

Aqueous solutions of anionic surfactant, sodium oleate (NaOA), have been studied by means of steady-state shear rheology and dynamic oscillatory technique. The micellar structure can be changed upon the addition of NaCl, Na₂CO₃ and NaCl/NaOH while NaOA concentration is maintained at 0.060 M. These systems except NaOA/NaCl show high viscosity and strong viscoelasticity. The hydroxide ion is very important for the formation of wormlike micelles. The anions of salts also have effect on the rheological properties of wormlike micelles. Three parameters: intersection frequency ω_i, plateau modulus G₀ and relaxation time τ are also discussed. The Maxwell model and Cole-Cole plot are applied to investigate the dynamic viscoelasticity of wormlike micelles. Variation in surfactant packing parameter R_P can be used to explain the change of rheology and microstructure of the micelles.     

TBAB/KCl对构筑阴离子蠕虫状胶束的影响

采用流变测试技术考察了两种阴离子表面活性剂油酸钠(NaOA)和芥酸钠(NaOEr)在四丁基溴化铵(TBAB)和KCl诱导下构筑蠕虫状胶束的行为.随着KCl浓度增加, NaOA水溶液粘度增加,而加入TBAB使NaOA-KCl样品的粘度持续降低.与之相反, TBAB浓度的增加却使NaOEr-KCl样品的粘度大幅度增强.此外, NaOEr分子比NaOA表现出更强的形成胶束的能力,构成粘弹性蠕虫状胶束所需表面活性剂浓度和盐浓度更少.本文采用TBAB和KCl两种盐协同诱导NaOEr,制备了具有强粘弹性的阴离子蠕虫状胶束,探讨了盐TBAB/KCl对长链阴离子表面活性剂构筑蠕虫状胶束的影响机理.     

Preparation of CO2 responsive wormlike micelles and the effect of hydrogen bond on the strength of the network

We first prepared two types of CO₂-responsive wormlike micelles based on N-butyldiethanolamine–sodium oleate (BDEA–NaOA) and N,N-diethyl butylamine–sodium oleate (DEBA–NaOA), respectively. And then, we compared the two different systems to investigate the effect of hydrogen bond on the properties of wormlike systems. The results of the pH and conductivity variation show that tertiary amine groups on BDEA and DEBA were ionized to quaternary ammonium salts after bubbling of CO₂ into the systems, which work with OA^? to form wormlike micelles based on electrostatic interaction. The results of rheological measurements exhibit that the viscosity and viscoelastic of the BDEA–NaOA were obviously superior to DEBA–NaOA. The dramatically difference of the two kind of wormlike micelles was due to the strong intermolecular hydrogen bond between the BDEA and NaOA. This indicates that the hydrogen bond could show great effect on the properties of the wormlike micelles. Finally, a reasonable mechanism was proposed based on the molecular structure, micelles assembly, and the intermolecular interactions.     

由碳酸钠诱导形成的油酸钠蠕虫状胶束的流变学性质

当Na₂CO₃浓度逐渐增加时, 用流变学的方法研究了阴离子表面活性剂油酸钠(NaOA)在溶液中从胶束转变成蠕虫状胶束的过程. 首先测量体系剪切粘度(η)和剪切速率的关系得到零剪切粘度(η₀). 然后由动态振荡实验得到复合粘度(|η^*|)、动态模量(储能模量G'、损耗模量G"和结构松弛时间τ_s)等物理量. 应用Cox-Merz规则和Cole-Cole图, 证明NaOA (0.040～0.080 mol/L)/Na₂CO₃ (0.25～0.50 mol/L)体系形成蠕虫状胶束, 且蠕虫状胶束的动态粘弹性在NaOA (0.050～0.080 mol/L)/Na₂CO₃ (0.35～0.45 mol/L)范围是符合Maxwell模型的线性粘弹性流体.     

疏水缔合聚丙烯酸与蠕虫状胶束的协同作用

从宏观流变性和介观尺度方面, 研究了疏水缔合聚丙烯酸(HMPA)与油酸钠(NaOA)构筑的蠕虫状胶束的协同作用. 考察HMPA对蠕虫状胶束溶液流变性和表观粘度的影响, 结果表明, 极少量HMPA的引入导致蠕虫状胶束溶液体系动态模量明显增加; 其表观粘度随HMPA浓度的增加先增强后减弱. 另一方面, 通过耗散颗粒动力学(DPD)分子模拟方法研究了混合体系中溶液组成对HMPA分子链的均方根末端距的影响. 结果表明,随着NaOA浓度增加, HMPA的均方根末端距会出现峰值; HMPA的伸展程度受其自身浓度变化制约, 相对于纯HMPA体系, NaOA胶束的存在对高浓度区的HMPA伸展程度影响更明显. 结合流变实验和分子模拟结果,初步解释了聚合物与蠕虫状胶束的协同作用机制.     

New type flooding systems in enhanced oil recovery

Wormlike micelles, obtained in anionic surfactant 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.     

Metal-driven viscoelastic wormlike micelle in anionic/zwitterionic surfactant systems and template-directed synthesis of dendritic silver nanostructures

In this work, metal ion-induced viscoelastic wormlike micelles in anionic/zwitterionic surfactant solutions (sodium dodecylsulfate/tetradecyldimethylammoniumpropanesulfonate, SDS/TPS) are reported. Steady and dynamic rheology and cryogenic transmission electron microscopy (cryo-TEM) are employed to characterize wormlike micelles in the SDS/TPS/Ca(NO(3))(2) system. Moreover, the surfactant mixing ratio and surfactant tail length are varied to reveal the factors that influence wormlike micelle growth and solution viscoelasticity. A series of metal ions such as Na(+), Mg(2+), Zn(2+), and Al(3+) are proven to promote viscoelastic wormlike micelle formation in the SDS/TPS system. The metal-containing wormlike micelles are expected to be good candidates for directing the synthesis of inorganic nanomaterials. In this article, dendritic silver nanostructures have been prepared in the surfactant wormlike micelle by in situ UV irradiation for the first time.     

Rheological Properties of Wormlike Micelles Formed by Cetyltrimethylammonium Bromide and Sodium Laurate

Aqueous solutions of mixed cationic and anionic surfactants, cetyltrimethylammonium bromide (CTAB) and sodium laurate (SL), have been studied by steady-state rheology and dynamic oscillatory technique. Wormlike micelles can form due to attractive interactions between the oppositely charged headgroups of CTAB and SL. The wormlike micelles formed by CTAB/SL have been compared with that of cetylpyridinium bromide (CPB)/SL by steady-state rheology method. Effects of additional components such as NaBr, 1-propanol, 1-butanol, polyvinylpyrrolidone (PVP) on the micelles formation process have also been investigated. Cole-Cole plot has been applied to study the dynamic viscoelasticity of the wormlike micelles.     

Anionic wormlike micellar fluids that display cloud points: rheology and phase behavior

We report our investigations into the self-assembly of sodium oleate (NaOA) in the presence of a binding salt (triethylammonium chloride, Et(3)NHCl) simple salt (potassium chloride, KCl). Both salts promote the growth of long, wormlike micelles in NaOA solutions, thereby increasing the fluid viscosity. The significant difference with the Et(3)NHCl salt is that it also modifies the phase behavior of NaOA solutions. Specifically, NaOA/Et(3)NHCl solutions display cloud points upon heating, followed by phase separation into two liquid phases. Such cloud point behavior is rarely observed in ionic surfactant systems, although it is common in nonionic surfactant solutions. Interestingly, while cloud points are not observed with KCl, the addition of KCl to NaOA/Et(3)NHCl solutions further lowers the cloud point temperature. Also, in the case of tetraethylammonium halide salt, neither a cloud point nor an increase in viscosity is observed. The clouding in the case of Et(3)NHCl is attributed to the temperature-induced aggregation of anionic micelles whose surface is covered by bound counterions.     

CO2 responsive wormlike micelles based on sodium oleate,potassium chloride and N,N-dimethylethanolamine

The anionic surfactant sodium oleate (NaOA) can self-assemble in aqueous solution in the presence of counter-ion inorganic salts to form wormlike micelles (WLMs), which exhibited viscoelastic behavior. In this paper, KCl was used to induce the formation of wormlike micelles with sodium oleate. In this process, we found that the addition of N, N-dimethylethanolamine (DMEA) can destroy the structure of WLMs leading significant decrease of viscosity. However, after introducing CO₂ into the ternary solution (KCl-NaOA-DMEA), the WLMs can be regenerated due to the electrostatic interaction between the protonated DMEA and the anionic surfactants. The addition of sodium hydroxide (NaOH) causes the electrostatic interaction between OA^- and DMEAH⁺ be destroyed, which results in the wormlike micelles becoming spherical micelles of lower viscosity. The transition of WLMs with high viscosity and low viscosity spherical micelles can be repeated several times by using CO₂ and NaOH.     

CO2-Responsive wormlike micelles based on sodium oleate and hydrophobic tertiary amines

We reported two simple and novel CO₂-responsive surfactant wormlike micellar systems consisting of commercial anionic surfactant sodium oleate (NaOA) and common hydrophobic tertiary amine N,N-dimethylcyclohexylamine (DMCHA), N,N-dimethylbenzylamine (DMBA). The conductivity, pH, and rheological measurements demonstrated the CO₂-sensitive flowing behavior and property, which were attributed to the spherical-wormlike micelles transition, verified by cryogenic transmission electron microscopy (Cryo-TEM) and dynamic laser light scattering (DLS) measurements. Moreover, the transition can be easily cycled more than three times without deterioration of viscosity. Combined with the species distribution curve and ¹H NMR spectra, a mechanism of the intermolecular electrostatic interaction and hydrophobic effects was proposed.     

Control of viscoelasticity using redox reaction

The viscoelasticity of a fluid was tuned with the Faradaic reaction of (11-ferrocenylundecyl)trimethylammonium bromide (FTMA), a "redox-switchable" surfactant. An aqueous solution of the reduced form of FTMA exhibited a remarkable viscoelasticity in the presence of sodium salicylate (NaSal) because of the formation of three-dimensional entanglement of wormlike micelles. Electrolytic oxidation of FTMA caused the viscosity of the system to dramatically decrease and the elasticity to disappear. This drastic decrease in viscoelasticity arose from the disruption of wormlike micelles. This novel electrorheological phenomenon is expected to be applicable to ink for inkjet printers, the electrochemically controlled release of substances entrapped in wormlike micelles of FTMA, and fluid flow rate control using electric signals.     

非离子表面活性剂Brij 30诱导离子液体型表面活性剂C16imC8Br蠕虫状胶束向凝胶的转变

Wormlike micelles and low-molecular-weight hydrogels are composed of three-dimensional networks that endow them with viscoelasticity, but their viscoelastic properties are markedly different. The viscosity of wormlike micelles is attributed to a transient network, while that of gels is due to a stable network. Under certain conditions, wormlike micelles can undergo transition to gels with an increase in the density of the network. In our previous study, we found that the wormlike micelle formed by the ionic liquid-type surfactant 1-hexadecyl-3-octyl imidazolium bromide ([C₁₆imC₈]Br) without any additive has high viscoelasticity. The inclusion of a nonionic surfactant polyoxyethylene lauryl ether (Brij 30) is expected to enhance the viscoelasticity of [C₁₆imC₈]Br wormlike micelles via electrostatic shielding and strong hydrophobic interactions, which may be the driving factor for the wormlike micelle-to-gel structural transition. The morphology and viscoelasticity of [C₁₆imC₈]Br wormlike micelles with Brij 30 were studied as a function of concentration by rheological measurements and freeze-fracture transmission electron microscopy. The thermal stability and gel-sol transition temperature of the Brij 30/[C₁₆imC₈]Br gels were studied using rheology. The interaction between Brij 30 and [C₁₆imC₈]Br was studied by zeta potential measurements and nuclear magnetic resonance (NMR) spectroscopy. Upon the inclusion of Brij 30 into the [C₁₆imC₈]Br wormlike micelles, the viscoelasticity of the Brij 30/[C₁₆imC₈]Br samples first increased and then decreased with an increase in the Brij 30 concentration, at different initial concentrations of [C₁₆imC₈]Br. At a certain Brij 30 concentration, the Brij 30/[C₁₆imC₈]Br samples rheologically behaved as a gel. The maximum viscoelasticity of the [C₁₆imC₈]Br (4.06% (w))/Brij 30 gel was observed at a Brij 30/[C₁₆imC₈]Br molar ratio of 4.55. The viscoelasticity of the Brij 30/[C₁₆imC₈]Br gels was positively correlated with the activation energy of the gels. The gel-sol transition temperature of the Brij 30/[C₁₆imC₈]Br gels also increased first and then decreased with an increase in the Brij 30 concentration. The highest gel-sol transition temperature of the Brij 30/[C₁₆imC₈]Br (4.06% (w)) gel was observed at a Brij 30/[C₁₆imC₈]Br molar ratio of 2.93. The Brij 30 concentration had a notable impact on the viscoelasticity, thermal stability, and gel-sol transition temperature of the Brij 30/[C₁₆imC₈]Br gels. The zeta potential and ¹H NMR measurements revealed that the neutral Brij 30 molecules are inserted into the palisade layer of the [C₁₆imC₈]Br wormlike micelles via hydrophobic interactions. This decreased the electrostatic repulsion between the [C₁₆imC₈]Br headgroups, which in turn induced the rapid growth of wormlike micelles and the formation of a stiffer network structure. Finally, the wormlike micelles underwent a structural transition to gels. The obtained results would aid in better understanding the relationship between wormlike micelles and gels, and may be of potential value for industrial and technological applications.     

阴离子蠕虫胶束

本文从分析蠕虫胶束形成的分子几何条件和自由能驱动因素入手,总结了传统阴离子表面活性剂蠕虫胶束的形成和性质,指出制约其构筑和产生优良黏弹性的原因。在此基础上,介绍了Gemini表面活性剂构筑蠕虫胶束的分子结构优势,以及由此构筑阴离子蠕虫胶束的研究进展,尤其是长刚性联接链Gemini表面活性剂形成的蠕虫胶束。最后特别指出,基于新颖分子结构优势,Gemini表面活性剂可望成为蠕虫胶束构筑的主要分子对象。     

A dually effective inorganic salt at inducing obvious viscoelastic behavior of both cationic and anionic surfactant solutions

Hydrazine nitrate (HN), an inorganic salt, was first found to have dual effects on inducing obvious viscoelasticity of both cationic and anionic surfactant solutions. It was interesting that the surfactant solutions exhibited characteristic wormlike micelle features with strong viscoelastic properties upon the addition of this inorganic salt. The rheological properties of the surfactant solutions have been measured and discussed. The apparent viscosity of the solutions showed a volcano change with an increase of the HN concentration. Correspondingly, the microstructures of the micelles in the solutions changed with the apparent viscosity. First, wormlike micelles began to form and grew with an increase of the HN concentration. Subsequently, the systems exhibited linear viscoelasticity with characteristics of a Maxwell fluid in the intermediate mass fraction range, which originated from a 3D entangled network of wormlike micelles. Finally, a transition from linear micelles to branched ones probably took place at higher HN contents. In addition, the origin of the dual effects brought by HN addition on inducing viscoelasticity in both cationic and anionic surfactant solutions was investigated.     

三聚阴离子表面活性剂/阳离子添加剂混合体系的流变行为

表面活性剂的分子结构对蠕虫胶束的形成与性质有着重要影响。本文以十四酸和间苯三酚为起始原料,合成了一种三聚阴离子表面活性剂（2, 2', 2"-（苯基-1, 3, 5-三（氧））-三-十四酸钠,简写为Ph-TrisC₁₄Na）,并通过稳态和动态流变测试,研究了单组分的Ph-TrisC₁₄Na和Ph-TrisC₁₄Na/阳离子添加剂体系的粘弹性质。阳离子添加剂分别为正丁基三甲基溴化铵（C₄TAB）,正己基三甲基溴化铵（C₆TAB）和正辛基三甲基溴化铵（C₈TAB）。结果表明,依赖于独特的分子构型,Ph-TrisC₁₄Na分子自身即可形成蠕虫胶束,使溶液表现出明显的粘弹性。阳离子添加剂的加入可进一步优化Ph-TrisC₁₄Na的分子几何结构,促进蠕虫胶束更为快速地生长。随着阳离子添加剂疏水链长的增加,溶液的粘弹性显著增强,体系微结构对添加剂的敏感性也增加。对于50 mmol·L^-1的Ph-TrisC₁₄Na溶液来说,在C₈TAB与Ph-TrisC₁₄Na的摩尔比为0.5时,体系的零剪切粘度可达1535 Pa·s,蠕虫胶束的长度则达到4.0-7.5 μm。该体系体现出低聚表面活性剂在构筑表面活性剂粘弹溶液方面的优势,可拓展高粘弹性阴离子蠕虫胶束体系的研究范围。     

Rheological Properties of Anionic Surfactant Solutions in the Presence of Al3+ Counterion

Aqueous solutions of ionic surfactants with strongly binding counterions exhibit wormlike or network properties. The properties of anionic micelles of sodium dodecyltrioxyethylene sulfate (AES) in the presence of multivalent counterion Al³⁺ were investigated by dynamic rheological methods. The steady-shear viscosity and stress, the zero-shear viscosity, the complex viscosity, and the dynamic shear modulus have been determined as a function of the surfactant and salt concentrations. Some interesting and noticeable results have been obtained, which can express the micellar growth and structure. The formation of wormlike micelles or network structure in surfactant solutions becomes much easier with increasing surfactant and salt concentrations. The Cox-Merz rule and the Cole-Cole plot are not applicable perfectly to the systems studied. The nonlinear viscoelasticity and non-Newtonian behavior can be found in all solutions according to the comparison with the simple Maxwell model. The technique of freeze-fracture transmission electron microscopy (FF-TEM) was also applied to confirm the formation of these interesting structures.     

CO2/N2-switchable viscoelastic fluids based on a pseudogemini surfactant system

We prepared a CO₂/N₂-switchable pseudogemini surfactant system composed of sodium oleate (NaOA) and N, N, N’, N’-tetramethyl-1, 6-hexanediamine (TMHDA) at a mole ratio of 2:1. The two tertiary amine groups of the TMHDA can be protonated into quaternary ammonium salt when the system was bubbled with CO₂, which can ‘‘bridge’’ two NaOA molecules via electrostatic attraction to form a pseudogemini surfactant. The formed pseudogemini surfactant can further self-assemble to wormlike micelles, causing a sharp increase in viscosity. The viscoelastic property and structure transitions of the pseudogemini surfactant system were investigated before and after bubbling of CO₂. The pseudogemini surfactant system transformed from water-like to gel-like fluid with the bubbling of CO₂, followed by white precipitate. The cryo-transmission electron microscope (cryo-TEM) characterization and rheological measurements exhibited that the sol–gel transition was attributed to a spherical-wormlike micelle transition. Moreover, this transition was switchable at least in three cycles. Finally, a reasonable mechanism of aggregate behavior transition was proposed from the viewpoint of the molecular states, micelle structures, and intermolecular interactions.     

Polymerization of anionic wormlike micelles

Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles.     

Dynamic light scattering from non-entangled wormlike micellar solutions

The fuzzy cylinder theory, originally proposed for conventional polymer solutions, was applied to wormlike micellar solutions to take into account effects of the intermicellar collision and hydrodynamic interaction on the self-diffusion of wormlike micelles in solution at finite concentrations. Previously reported apparent hydrodynamic radius data obtained by dynamic light scattering for non-entangled wormlike micelles formed in aqueous solution by non-ionic surfactants, polyoxyethylene monoalkyl ethers C(i)E(j), were analyzed by this theory to estimate the persistence length q of the wormlike micelles. The results of q estimated were consistent with those obtained from radius of gyration data obtained by static light scattering.