部分水解聚丙烯酰胺与蠕虫状胶束在微米级毛细管中的驱替粘度（英文）

部分水解聚丙烯酰胺(HPAMs)被大量地用作三次采油中驱替液的增稠剂,表面活性剂在一定的条件下可以通过自组装形成蠕虫状胶束,具有与高分子相似的增稠的作用。本文在半径为1–10μm的毛细管中,分别考察了HPAMs与蠕虫状胶束的微观驱替行为,研究结果表示毛细管内腔的尺寸限制了这些非牛顿流体的增稠作用。随着毛细管半径的减小,聚合物溶液的剪切变稀越剧烈,甚至从非牛顿流体转变为牛顿流体的流体行为。结合驱替研究和超滤、电镜的结果,证明了高分子的缠绕结构在毛细管中已被破坏。通过对比驱替数据,蠕虫状胶束在毛细管中能够更大程度地保留宏观的粘度,我们提出表面活性剂能够通过自组装修复被破坏的缠绕结构,比高分子聚合物在微观有限空间中有更好的增稠能力。     

十六烷基三甲基溴化铵/油酸钠混合体系蠕虫状胶束流变性研究

阴、阳离子表面活性剂之间强烈的相互作用利于形成自由弯曲的蠕虫状胶束。本文利用阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)和阴离子表面活性剂油酸钠(Na OA)制备了CTAB/Na OA蠕虫状胶束,研究了两表面活性剂的混合比和表面活性剂总浓度的变化对蠕虫状胶束体系稳态流变性及动态粘弹性的影响。结果表明,蠕虫状胶束在剪切过程中的解缠、拟网状结构的破坏以及最终沿剪切速度方向取向等是蠕虫状胶束产生剪切稀释特性的原因。两表面活性剂的混合比和表面活性剂总浓度的变化导致表面活性剂之间的静电作用、疏水作用发生较大的变化,最终引起体系内部表面活性剂聚集体形态的差异。体系内蠕虫状胶束长度、体系结构复杂程度、蠕虫状胶束形成的网络结构的致密度等都影响着体系的流变行为。在混合比R=3.6、总浓度CT=0.24mol/L时,体系中蠕虫状胶束最长,网络结构最为紧密,体系的零剪切粘度达到最大值。表面活性剂浓度一定时,混合比的提高有助于蠕虫状胶束的定向生长,弛豫时间τR和储能模量高频区平台模量G0提高,R=3.6时两者皆达到极大值,此后由于蠕虫状胶束的分枝化及(或)胶束破裂导致τR及G0下降。在表面活性剂混合比一定(R=3.6)时,表面活性剂浓度的提高利于蠕虫状胶束的增长或者分枝化,增加了胶束网络结构缠绕(融合)点的密度,导致G0逐渐增大。Cole-Cole图证实本文研究的蠕虫状胶束体系是符合Maxwell模型的线性粘弹性流体。     

粘弹性蠕虫状胶束及其应用

介绍了粘弹性蠕虫状胶束的形成、类型、基本性质及其应用情况.粘弹性蠕虫状胶束具有重要的微观结构,因其特殊的流变性能而在不同领域具有重要应用.最近,蠕虫状胶束的结构和动态性质的研究已经延伸到不同类型的表面活性剂,如阴离子、两性离子和聚合物表面活性剂.目前,其应用领域已经拓展到油田、社区冷热流体的减阻、个人护理和家庭清洁产品的增稠剂等方面.     

两性/阴离子表面活性剂形成具有耐盐性能的蠕虫状胶束

利用流变学方法研究了两性表面活性剂十四烷基磺基甜菜碱(TDAPS)和阴离子表面活性剂十二烷基硫酸钠(SDS)混合体系中蠕虫状胶束的耐盐性能, 分析了二价金属离子对蠕虫状胶束微观结构的影响. 结果表明, 在加入MgCl₂和CaCl₂使Mg^2＋和Ca^2＋总浓度达到0～1900 mg/L的情况下, TDAPS/SDS体系中形成的蠕虫状胶束的粘弹性能和耐剪切能力不仅没有损失而且增强. 对静态流变和动态流变结果进一步分析表明体系中同时存在两种可区分尺寸的蠕虫状胶束. 加入二价金属离子, 体系的微观结构发生了由小尺寸蠕虫状胶束向大尺寸蠕虫状胶束转变, 同时, 大尺寸蠕虫状胶束线性增长并发生枝化. 两性表面活性剂头基上的正电荷中心减小了蠕虫状胶束的反离子结合程度, 抑制了线性生长到枝化生长的过程, 使体系表现出优异的耐盐性能.     

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.     

阴离子疏水缔合共聚物/阳离子蠕虫状胶束协同增粘自组装网络

将阴离子疏水缔合丙烯酰胺共聚物P(NaAMC14S-b-AM)与阳离子蠕虫状胶束十六烷基三甲基溴化铵/水杨酸钠(CTAB/NaSal)在水溶液中自组装制备了新型的缔合增粘体. 由稳态剪切和动态流变实验结果得出: 自组装体系在80 ℃下仍具有显著的协同增粘效应, 其流变行为符合Maxwell模型. 同蠕虫状胶束相比, 自组装体系的稳态模量G0、力学松弛时间τR和缠结点密度ν都有增加, 由此分析缔合体系中两组分间形成了相互缠结的网络结构, 在链缠结处共聚物主链上的疏水侧链嵌入到了蠕虫状胶束的内核.     

非离子型Y形两亲性聚氨酯水溶液自组装研究

设计并制备了Y形两亲性嵌段聚合物(mPEG)₂-HDI-PEA，以六亚甲基二异氰酸酯三聚体为反应物，分别与聚乙二醇单甲醚、聚醚胺进行官能团偶合生成Y形聚氨酯，其在水溶液中自组装行为。通过¹H NMR、FT-IR和GPC对分子结构进行表征，通过透射电镜(TEM)和原子力显微镜(AFM)对自组装形貌进行表征。聚合物(mPEG)₂-HDI-PEA在不同温度和不同浓度下自组装形成的聚集体形貌，表明分子间的氢键作用对聚集体形貌起着重要作用。(mPEG)₂-HDI-PEA嵌段聚合物在室温下自组装，形成新颖的形貌，表面具有“沟壑”的球状胶束，随着浓度增加形成的球状胶束表面“沟壑”越明显，排列越有序；当嵌段聚合物(mPEG)₂-HDI-PEA在60 ℃水溶液中自组装时，形成蠕虫状胶束，并随着浓度的增加从蠕虫状转变成网状；聚合物溶液在60 ℃环境中静置1个月后，在AFM下观测到蠕虫状胶束长度增加，当蠕虫装胶束从60 ℃冷却至室温胶束形貌、尺寸未改变，当稀释并静置在60 ℃3天后胶束从蠕虫状转变成棒状或者椭球状，展现出动态组装与解离的过程。      

疏水缔合和静电作用调控P(DTAB-co-AM)与蠕虫状胶束自组装网络

由新型的阳离子疏水单体二甲基十四烷基(3-丙烯酰胺基丙基)溴化铵(DTAB)与丙烯酰胺(AM)共聚合成了阳离子型疏水缔合共聚物P(DTAB-co-AM),研究了该共聚物与蠕虫状胶束自组装后的协同增黏效应,及改变疏水单体含量对自组装体系黏度的调控作用.制备了十八烷基三甲基氯化铵(CTAC)/水杨酸钠和芥酸钾/三羟乙基苄基氯化铵两类稳定的黏度较大的蠕虫状胶束体系.共聚物P(DTAB-co-AM)与芥酸钾/三羟乙基苄基氯化铵蠕虫状胶束在疏水缔合和静电吸引双重作用下自组装可形成协同增黏的缔合体系,而与CTAC/水杨酸钠阳离子蠕虫状胶束进行自组装由于只有疏水缔合作用,增黏效果不及前者.表观黏度研究表明,随着疏水单体含量的增加,P(DTAB-co-AM)与芥酸钾/三羟乙基苄基氯化铵缔合体系的黏度先增加后降低,当疏水单体含量为0.15 mol%时,缔合体系黏度达到极大值;当疏水单体含量为0.3 mol%时,缔合体系黏度反而低于与阳离子蠕虫状胶束缔合后的黏度.对于共聚物与CTAC/水杨酸钠蠕虫状胶束缔合体系,随着疏水单体含量增加,由于疏水缔合作用与静电排斥作用的相互抵消,致使体系黏度有所下降.由此说明改变疏水单体含量可以达到调控自组装体系黏度的目的.     

基于非共价键作用的二嵌段共聚物/均聚物超分子体系的自组装行为

采用实空间求解的自洽场理论,研究了两亲性二嵌段共聚物(AB)/均聚物(C)超分子体系在溶液中的自组装行为,其中B疏水嵌段的自由末端与C均聚物的一个末端形成可逆的非共价键.在稀溶液中,AB/C超分子聚合物体系通过自组装形成了一系列不同形貌的胶束,如核-壳-冠的三层胶束和蠕虫状胶束等.研究发现,胶束形貌受到非共价键强度和初...     

长链阳离子表面活性剂蠕虫状胶束的剪切带转变行为研究

报道一种含有不饱和疏水尾链的超长链阳离子表面活性剂——N-芥酸酰胺丙基-N,N,N-三甲基碘化铵(EDAI)自组装所形成的蠕虫状胶束及其剪切带行为. EDAI浓溶液表现出了明显的剪切带转变特征, 即溶液的流动曲线被介于两个临界剪切速率之间的剪切应力平台分割为粘度不同的两部分. 在剪切带转变区域, 原本均质的流体表现出机械剪切不稳定性, 沿速度梯度方向被分割为剪切速率不同的两个宏观流体层.     

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.     

Effects of surfactant micelles on viscosity and conductivity of poly(ethylene glycol) solutions

The neutral polymer-micelle interaction is investigated for various surfactants by viscometry and electrical conductometry. In order to exclude the well-known necklace scenario, we consider aqueous solutions of low molecular weight poly(ethylene glycol) (2-20)x10(3), whose radial size is comparable to or smaller than micelles. The single-tail surfactants consist of anionic, cationic, and nonionic head groups. It is found that the viscosity of the polymer solution may be increased several times by micelles if weak attraction between a polymer segment and a surfactant exists, epsilon相似文献   

Synergistic effects in flows of mixtures of wormlike micelles and hydroxyethyl celluloses with or without hydrophobic modifications

This work presents experimental results on simple shear and porous media flow of aqueous solutions of two hydroxyethyl celluloses (HEC) and two hydrophobically modified hydroxyethyl celluloses (HMHEC) with different molecular weights. Mixtures of these polymers with a cationic surfactant, cetyltrimethylammonium p-toluenesulfonate (CTAT) were also studied. Emphasis was given to the range of surfactant concentrations in which wormlike micelles are formed. The presence of hydrophobic groups, the effect of the molecular weight of the polymers, the surfactant and polymer concentrations, and the effect of the flow field type (simple shear versus porous media flow) were the most important variables studied. The results show that the shear viscosity of HEC/CTAT solutions is higher than the viscosities of surfactant and polymer solutions at the same concentrations, but surface tension measurements indicate that no complex formation occurs between CTAT and HEC. On the other hand, a complex driven by hydrophobic interactions was detected by surface tension measurements between CTAT and HMHEC. In this case, the viscosity of the mixture increases significantly more (up to four orders of magnitude at high CTAT concentrations) in comparison with HEC/CTAT aqueous solutions. Increments in the molecular weight of the polymers increase the interaction with CTAT and the shear viscosity of the solution, but make phase separation more feasible. In porous media flow, the polymer/CTAT mixtures exhibited higher apparent viscosities than in simple shear flows. This result suggests that the extensional component of the flow field in porous media flows leads to a stronger interaction between the polymer and the wormlike micelles, probably as a consequence of change of conformation and growth of the micelles.     

Surfactant-based gels

This article reviews known approaches to generating viscoelastic and gel-like surfactant systems focusing on how the formation of these viscous phases are often sensitive to a variety of chemical and physio-chemical factors. An understanding of this sensitivity is essential for generating high viscosity surfactant phases in more challenging solvent environments. The initial focus is on the generation of worm-like and reverse worm-like micelles. In addition, other approaches for using surfactant self-assembly for viscosity enhancement have been examined, namely gelatin microemulsion based organogels and the addition of substituted phenols to AOT reverse micelles.     

New dendronized polymers from acrylate Behera amine and their ability to produce visco-elastic structured fluids when mixed with CTAT worm-like micelles

Two new water soluble dendronized polymers (PLn) from acrylate Behera amine monomer of different molecular weights were successfully synthesized. The polymers were characterized by FTIR, NMR, GPC and DLS. Both GPC and DLS results indicated that these PLn have a remarkable tendency to form aggregates in solution that lead to apparent molecular weights that are much higher than their theoretical values, as well as large diameters in solution. However, the addition of any PLn to water did not cause any increase in viscosity up to concentrations of 1000 ppm. The possible interactions of PLn with the cationic surfactant CTAT were explored by solution rheometry. A synergistic viscosity enhancement was found by adding small amounts of dendronized PLn polymers to a CTAT solution composed of entangled worm-like micelles. The highest association tendency with CTAT was found for PL1 at the maximum polymer concentration before phase separation (i.e., 100 ppm). The solution viscosity at low-shear rates could be increased by an order of magnitude upon addition of 100 ppm of PL1 to a 20mM CTAT solution. For this mixture, the fluid obtained was highly structured and exhibited only shear thinning behavior from the smallest shear rates employed. These PL1/CTAT mixtures exhibited an improved elastic character (as determined by dynamic rheometry) that translated in a much longer value of the cross-over relaxation time and a pronounced thixotropic behavior which are indicative of a strong intermolecular interaction. In the case of the polymer with a higher theoretical molecular weight, PL2, its association with CTAT leads to an extraordinary doubling of solution viscosity with just 0.25 ppm polymer addition to a 20mM CTAT solution. However, such synergistic viscosity enhancement saturated at rather low concentrations (25 ppm) indicating an apparent lower solubility as compared to PL1, a fact that may be related to its higher molecular weight.     

Rheology of viscoelastic solutions of cationic surfactant. Effect of added associating polymer

Rheological studies were performed with aqueous salt solutions of viscoelastic cationic surfactant erucyl bis(hydroxyethyl)methylammonium chloride (EHAC) and its mixtures with hydrophobically modified polyacrylamide. The solutions of surfactant itself above the concentration of crossover of wormlike micelles exhibit two regions of rheological response. In the first region, they behave like polymer solutions in semidilute regime characterized by viscoelastic behavior with a spectrum of relaxation times. In the second region, unlike polymer solutions their relaxation after shear is dominated by a single relaxation time. Being composed of "living" micelles, the EHAC solutions easily lose their viscosity at the variation of the external conditions. For instance, heating from 20 to 60 degrees C reduces viscosity by up to 2 orders of magnitude, while added hydrocarbons induce a sudden drop of viscosity by 3-6 orders of magnitude. Polymer profoundly affects the rheological properties of EHAC solutions. The polymer/surfactant system demonstrates a 10,000-fold increase in viscosity as compared to pure-component solutions, the effect being more pronounced for polymer with less blocky distribution of hydrophobic units. A synergistic enhancement of viscosity was attributed to the formation of common network, in which some subchains are made up of elongated surfactant micelles, while others are composed of polymer. At cross-links the hydrophobic side groups of polymer anchor EHAC micelles. In contrast to surfactant itself, the polymer/surfactant system retains high viscosity at elevated temperature; at the same time it keeps a high responsiveness to hydrocarbon medium inherent to EHAC.     

Viscosity behavior of silica suspensions flocculated by associating polymers

Associating polymers are hydrophilic long-chain molecules containing a small number of hydrophobic groups, and act as flocculants in aqueous suspensions. The effects of associating and nonassociating polymers on viscosity behavior are studied for silica suspensions. Since flocculation is induced by polymer bridging, the viscosity behavior is converted from Newtonian to shear-thinning profiles. The additions of surfactant cause an increase in viscosity for suspensions prepared with associating polymer, whereas the flow behavior of suspensions with nonassociating polymer is not significantly influenced. In adsorption of associating polymers onto silica particles, the chain may adopt a conformation with a water-soluble backbone attached to the particle surfaces. The hydrophobic groups extending from the chains adsorbed onto different particles can form a micelle by association with surfactant. Therefore, the bridging flocculation is enhanced by surfactant. The cooperative micellar formation between associating polymer and surfactant is responsible for viscosity increase in suspensions.     

联接基长度对Gemini表面活性剂流变性质的影响

用毛细管振荡剪切流动法研究了联接基团为聚亚甲基链的阳离子Gemini表面活性剂的流变性质。实验结果表明,无论是普通单链单头基或Gemini表面活性剂,其流变性质主要由胶团的大小和形状所决定;随着联接基团长度的增加,胶团的轴比率变小,导致流动阻力减小,粘度降低。此外对于球形和棒状胶团溶液,其流变性质主要以粘性为主．弹性可忽略不计。在低剪切速率下,溶液属于牛顿型流体;而在高剪切速率下,则表现出准塑性流体性质。     

INTERACTIONS BETWEEN CATIONIC STARCH AND ANIONIC SURFACTANTS III RHEOLOGY AND STRUCTURE OF THE COMPLEX PHASE

This paper reports on studies of the rheological properties of cationic starch (CS)/ surfactant systems. The degree of substitution of the CS was 0.1 - 0.8. Surfactants investigated were sodium dodecyl sulfate (SDS), potassium octanoate (KOct), sodium decanoate (NaDe)potassium dodecanoate (KDod), sodium oleate (NaOl) and sodium erucate (NaEr). Aggregation of surfactant micelles with the polymer produces a hydrophobic and pseudoplastic gel-like complex phase with low water content and high viscosity. The rheological behavior of the gels is described by the Herschel-Bulkley model. In dilute aqueous solution the CS/surfactant aggregate structure resembles a randomly coiled polymer network, in which polymer molecules are linked by micelles. The rheological data for the gel are compatible with the assumption that the surfactants form liquid crystalline structures with the polymer anchored to the surfactant aggregates, as recently suggested for analogous systems. However, this conjecture needs to be corroborated by more direct determinations of the structure.     

Mobility op polymer micelles

The nanosecond mobility of polymer micelles in aqueous solution of poly(N-propylmethacrylamide) and that of reversed micelles of a surfactant in organic solvents were studied by polarized luminescence. The factors affecting the polymer micelles formation and the effect of polymers solubilized in systems of reversed micelles of a surfactant on their relaxation properties were established.