Interfacial Dilational Rheology of Sodium Lauryl Glycine and Mixtures with Conventional Surfactants

Amino acid-based surfactants are environmentally friendly surfactants, which have aroused increasing interest. In the application of amino acid-based surfactants, they are often compounded with other kinds of surfactants to obtain formulations that meet certain requirements. Herein, sodium lauroyl glycinate (C12-Gly-Na) was selected as a representative amino acid-based surfactant to compound with an anionic surfactant (sodium dodecyl sulfate [SDS]), a cationic surfactant (dodecyl trimethyl ammonium Bromide), and a nonionic surfactant (Triton X-100: p-octyl polyethylene glycol phenyl ether). Surface tension measurements and interfacial dilational rheological experiments were performed to study the interfacial behaviors of C12-Gly-Na and its mixtures. The results show that mixture systems have better interfacial activity than individual C12-Gly-Na and there is an obvious synergy between C12-Gly-Na and C12TAB under strong electrostatic attraction. Thus, the C12-Gly-Na/C12TAB mixture shows lower critical micelle concentration (CMC) and γ_CMC and higher dilational modulus than the individual surfactants. Besides, the film formed by the C12-Gly-Na/C12TAB mixture has higher viscoelasticity than single C12-Gly-Na and its mixtures with SDS and TX-100. With the increase of bulk concentration, the dilational moduli of C12-Gly-Na, C12-Gly-Na/SDS, and C12-Gly-Na/TX-100 run through two maxima, while, due to stronger electrostatic attraction, only one maximum appears in the C12-Gly-Na/C12TAB system. The study of the interfacial properties of amino acid surfactant and its mixtures with other surfactants provides a theoretical foundation for potential applications in cosmetic, food processing, and daily chemical industries.     

Effects of Divalent Salts on the Interfacial Activity of the Mixed Surfactants at the Water/Model Oil Interface

In our previous report, the mixed cationic/anionic surfactant system consisting of N-dodecyl-N-methylpyrrolidinium bromide (L12) and sodium dodecyl sulfate (SDS) showed good interfacial tension (IFT) reduction of water/model oil (V_toluene:V _n-decane = 1:1). In the present study, the effects of divalent salts (MgCl₂ or CaCl₂) on the interfacial activity were systematically evaluated. The additional Mg²⁺ ions greatly reduced the IFT to an ultralow value, whereas Ca²⁺ ions caused the generation of the precipitates and resulted in increased IFT values. The precipitates disappeared in binary divalent salt solutions, and the IFT values remained at a low level. Based on the valence, polarizability, and hydrated radius of the ions, we proposed a model to explain the abnormal changes. The effects of NaCl and temperature were investigated to further verify our proposed mechanism. Moreover, the additional divalent salts obviously enhanced the stability of L12/SDS stabilized emulsions.     

New Interfacial Rheology Characteristics Measured using a Spinning‐Drop Rheometer at the Optimum Formulation of a Simple Surfactant–Oil–Water System

A new spinning‐drop tensiometer with an oscillating rotation velocity was used to measure the interfacial rheological properties of systems with very low interfacial tensions in the zone close to the so‐called optimum formulation of surfactant–oil–water systems. 2 simple formulation scans were selected: One with an extended anionic surfactant using a salinity variation in the water phase, and another with a mixture of 2 nonionic surfactants in a scan produced by changing their proportion. With both systems it was corroborated that at optimum formulation (i.e., at hydrophilic–lipophilic deviation (HLD) = 0), both the interfacial tension and the emulsion stability exhibit a deep minimum. A clear relationship was also found between the phase behavior and the interfacial rheological properties (dilational elasticity and viscosity). For the very first time and in both kinds of scans (salinity or average ethylene oxide number), it was found that the interfacial elastic modulus E and the interfacial viscosity, as well as the phase angle also exhibit a minimum at optimum formulation. These groundbreaking findings could be applied to emulsion instability at optimum formulation and to its applications in emulsion breaking.     

两种Gemini表面活性剂在气／液界面的混合单分子膜

用Langmuir膜天平测定了双头基四疏水链的季铵盐Gemini表面活性剂2C12-8-2C12·2Br和羧酸型Gemini表面活性剂c11pPHCOOH在气／液界面的表面压(π)-每个分子平均占据面积(A)的等温线,考察了压缩模量(ε)、过剩面积(△AE)、过剩自由能(△GE)等热力学参数随混合体系组成的变化。结果表明,纯组分体系和混合体系均形成液相扩展态单分子膜,混合体系的组成显著影响气／液单分子膜的性质以及组成膜的分子之间的相互作用。     

Effect of Thermal Stability of Alkanolamide on Oil/Water Interfacial Tensions

In order to investigate the effect of thermal stability of alkanolamide on oil/water interfacial tensions (IFT), lauric diethanolamide (LDEA) was synthesized. The effects of temperature and standing time on the composition and oil/water IFT was studied in detail. The results showed that the changes in composition and oil/water IFT at the same conditions were essentially in agreement. The best standing temperature range was from 30 to 60 °C with a standing time of more than 10 days. The inherent cause of thermal stability on oil/water IFT was revealed through structure characterization and composition analysis with FTIR spectrometry and GC–MS spectrometry. It was found that the composition's change of mixed LDEA systems disturbed the hydrophilic‐lipophilic balance, which influenced the ability to reduce the interfacial tension.     

Study on the Adaptability of Alkanolamide (LDEA) Lowering Oil/Water Interfacial Tension to Different Crude Oils

In order to investigate the high interfacial activity and fair oil phase adaptability of alkanolamide, “1:1” type lauric acid diethanolamide impurities (LDEA) were synthesized and purified by the column chromatography method to obtain dodecanoic acid diethanolamide (C₁₂DEA), ester mixture, etc. The exact structures of these compounds were further confirmed by IR, gas chromatogrph with mass spectroscopy (GC–MS), and NMR. The influence of each component on the interfacial tension of oil/water (IFT) was studied by systematic quantitative analysis. The results showed that (i) the strength of each system to reduce oil/water IFT is C₁₂DEA /DEA ≈ LDEA > C₁₂DEA/DEA/ESTER > C₁₂DEA/NaOH > C₁₂DEA > C₁₂DEA/ESTER > DEA. This indicates that LDEA contributes to the reduction of the oil/water IFT and the enhanced adaptability of crude oil in this order: DEA > > ESTER; (ii) when the IFT of the LDEA/DEA system reached an ultralow value, the minimum content of DEA in the system was 1%, and the maximum ester content was less than 5% when the LDEA/DEA/ESTER system reached the ultralow IFT; (iii) the possible mechanism of effect of LDEA components on the IFT and oil phase adaptability was proposed as the synergistic process among the hydrogen bonding, alkali effect, and interface self-assembly of molecules in the interfacial layer. The contribution of these three factors were hydrogen bonding > alkali effect > interface self-assembly.     

Salt-Induced Constructions of Gemini-like Surfactants at the Interface and Their Effects on the Interfacial Tension of a Water/Model Oil System

It is an urgent issue to enhance oil recovery for unconventional reservoirs with high salinity. Focused on this topic, salt addition is a powerful tool to motivate the surfactant assembly at the water/oil interface and improve the interfacial activity. We used a cationic surfactant cetyltrimethylammonium bromide (CTAB) and an anionic salt dicarboxylic acid sodium (CnDNa) to construct gemini-like surfactants at the interface and evaluated their ability to reduce the interfacial tension (IFT) between model oil (toluene and n-decane, v:v = 1:1) and water. Interestingly, the fabrication of a (CTAB)₂/C4DNa gemini-like surfactant was hardly achieved at the fresh water/model oil interface, but accomplished at the brine/model oil interface. At a high NaCl concentration (100,000 mg L⁻¹), the IFT value is reduced to 10⁻³ mN m⁻¹ order of magnitude, which is generally desired in practical applications. The control experiments displacing the surfactant type and the spacer length further confirmed the NaCl effects on the interfacial assembly.     

表面活性剂在固液界面吸附研究的某些新进展

本文综述了离子型表面活性剂以及阳离子与非离子型表达活性剂的混合体系在固液界面吸附情况。     

Molecular Dynamics Study of the Behaviour of TBP-Zinc-Chloride Complex at the Chloroform/Water Interfacial System

We report molecular dynamics studies of TBP behavior at the interface. TBP, irrespective of the number particles as well as of initial orientation, adsorbs at the interface to occupy the maximum surface of this area. Polar part of the molecule is pointed towards the aqueous phase an alkyl chains are pointed to the organic phase. Some of the TBP particles are present in the organic phase as well. TBP is able to bond 3 to 4 water particles in the organic phase. We can notice the formation of the following dimers: (TBP)₂ · H₂O, (TBP · H₂O)₂, as well as the formation of “water fingers”. ZnCl₂(TBP)₂ complex also adsorbs at the interface. Polar part P?O→ZnCl₂←O?P is pointed towards water. Performed simulation show that the molecule of the complex is solvated by water particles as well. The obtained results correspond to the experimental ones.     

螺旋霉素的水／硝基苯界面循环伏安法研究及其测定

本文利用循环伏安法研究了螺旋霉素推动质子从水相向硝基苯相转移的过程，并建立了一种新的测定螺旋霉素有效含量的电化学方法     

Gemini表面活性剂在固液界面的吸附及增溶作用

介绍了一类新型表面活性剂———Gemini表面活性剂。这类表面活性剂具有特殊的分(离)子结构,其分(离)子由两(或三)条疏水链、两个亲水基和一个连接基组成。综述了Gemini表面活性剂在固液界面的吸附及增溶作用,其在固液界面的吸附及增溶作用与固体表面的性质及其分(离)子结构有很大关系。     

XSY-11双子表面活性剂提高采收率应用研究

通过测定双子表面活性剂与原油的界面张力,发现双子表面活性剂在缺碱的条件下,也可以使油水界面张力降低至超低的能力,证明了其对碱的依赖性较小,优于普通表面活性剂.单独使用双子表面活性剂或者与其他表面活性剂协同使用,均可以使多种原油-水界面张力降低至超低范围.对双子表面活性剂溶液浓度等因素对油水界面张力的影响程度进行了分析.发现双子表面活性剂降低油水界面张力的能力主要与表面活性剂和油的性质密切相关.研究了其界面张力行为,发现双子表面活性剂具有比普通表面活性剂较高的界面活性,并且与盐具有很好的协同性,可以在较宽的盐度和表面活性剂浓度范围内降低油水界面张力至超低范围.     

Quantifying Water at the Organic Film/Hydroxylated Substrate Interface

A method, based on Fourier transform infrared-multiple internal reflection (FTIR-MIR) spectroscopy, for determining the amount and thickness of water at an organic film/hydroxylated substrate interface has been developed. The analysis uses a two-layered model, which takes into account: 1) water at the organic film/hydroxylated substrate interface, 2) water taken up by the organic film within the penetration depth of the evanescent wave and 3) change of the penetration depth as water displaces the organic film from the substrate. Experimentally, the method requires the application of an organic film, transparent or opaque, of sufficient thickness on a hydroxylated internal reflection element, which is used as the substrate. A water chamber is attached to the organic-coated specimen. After adding water to the chamber, FTIR-MIR spectra are taken automatically at specified time intervals without disturbing the specimen or the instrument. Water uptake in the organic films and FTIR-MIR spectra of water on the substrates are also obtained and used for the analysis. Results of examples of three organic films: a clear epoxy, an unmodified asphalt, and a pigmented ester, on a hydroxylated SiO₂-Si substrate were presented to demonstrate the method. The water layer at the interface for the ester and asphalt specimens was found to be much thicker than that for the epoxy, and this was attributed to the presence of a water-sensitive layer accumulated at the interface for the formers. The method should be equally applicable to studies of organic and inorganic compounds at the organic film/hydroxylated substrate interface and their transport rates through films adhered to a substrate.     

Effects of Polyether Surfactants on Dynamic Interfacial Tension of Betaine Solutions against Crude Oil

The dynamic interfacial tension (IFT) of betaine and betaine/polyether‐nonionic surfactant‐mixed systems against hydrocarbons, kerosene, and crude oil–water was studied using a spinning‐drop tensiometer. The influence of average molecular weight of polyether‐nonionic surfactants on IFT of mixed solutions was investigated. On the basis of the experimental results, one can find that it is difficult to reach the ultralow IFT value for betaine solution against hydrocarbon and kerosene because of the mismatch between the hydrophobic and hydrophilic groups. After purification, kerosene still contains a small amount of carboxyl groups, which can exert a synergistic effect on surfactants resulting in a lower IFT. The IFT of betaine and mixtures against Daqing crude oil can reach an ultralow value because of the mixed adsorption of surfactant and petroleum soap molecules. For mixed solutions, with the increasing concentration of added polyether, the decrease of petroleum soaps at the oil–water interface results in the destruction of synergistic effects.     

粉·福（粉锈宁＋福美双）悬浮剂物理稳定性的研究

详细地研究了粉·福（粉锈宁＋福美双）悬浮剂的流变学行为,提出了用相对趋近值来判断悬浮体系的物理稳定性,并取得了良好的效果。     

Phospholipids at the Interface: Current Trends and Challenges

Phospholipids are one of the major structural elements of biological membranes. Due to their amphiphilic character, they can adopt various molecular assemblies when dispersed in water, such as bilayer vesicles or micelles, which give them unique interfacial properties and render them very attractive in terms of foam or emulsion stabilization. This article aims at reviewing the properties of phospholipids at the air/water and oil/water interfaces, as well as the recent advances in using these natural components as stabilizers, alone or in combination with other compounds such as proteins. A discussion regarding the challenges and opportunities offered by phospholipids-stabilized structure concludes the review.     

Design and Surface/Interfacial Properties of Asymmetric Triazine Carboxyl Betaine Surfactants

The design, synthesis and interfacial behaviors of six asymmetric carboxyl betaine surfactants (BC_m?n, m, n = 8, 10, 12, or 14, m ≠ n) derived from s‐triazine, which were prepared from cyanuric chloride, aliphatic amines, N,N‐dimethylpropane‐1,3‐diamine, followed by the reaction with sodium chloroacetate, are reported. The structures were confirmed by MS, ¹H NMR and FT‐IR. Compared with symmetric surfactants (BC_n?n, n = 8, 10, 12, or 14) we previously synthesized, the asymmetric series show superior surface activity. The γ_CMC of surfactants BC_10?8, BC_12?8, BC_14?8 and BC_12?10 is all below 30 mN/m. The minimum alkane carbon number of these ten surfactants is determined to be between 10 and 14. The interfacial behaviors between the alkanes and the solutions of triazine carboxyl betaine surfactants show that surfactants with a total carbon number in hydrophobic chains between 16 and 22 exhibit the ability to reduce the interfacial tension to an ultra‐low value (10^?3 mN/m). The surfactants with longer hydrocarbon chains display strong affinity to the alkanes with longer chains.     

Flow of two-phase oil/water mixtures through sudden expansions and contractions

Pressure loss data in a sudden expansion and a sudden contraction were obtained for two-phase oil/water mixtures, covering a wide range of oil concentration: 0 to 97.3 vol.% oil. The emulsions were of oil-in-water type up to an oil concentration of 64 vol.%. Above this concentration, the emulsions were water-in-oil type. An on-line conductance cell was used to monitor the inversion point and the type of emulsion. The pressure loss was determined from the measured pressure profiles upstream and downstream of the fitting. From the pressure-loss/velocity data, the loss coefficients were obtained. The loss coefficients for the emulsions are found to be independent of the concentration and type of emulsions. Furthermore, there is no observable difference between the loss coefficients for emulsions and single-phase water.     

Interfacial Tensions of Ethoxylated Fatty Acid Methyl Ester Solutions Against Crude Oil

The dynamic interfacial tension (IFT) of ethoxylated fatty acid methyl ester solutions against n‐alkanes, kerosene, and diluted heavy oil have been investigated by spinning drop interfacial tensiometry. The influences of ethylene oxide (EO) groups and alkyl chain length on IFT were investigated. The experiment results show that the water solubility decreases with an increase in alkyl chain length or a decrease in EO groups. The ability to lower the interfacial tension against hydrocarbons improves with both increasing alkyl chain length and EO group at the best hydrophilic‐lipophilic balance, which can be attributed to the enhancement of the interfacial hydrophobic interactions and the rearrangement of interfacial surfactant molecules. The mixed adsorption of surfactant molecules and surface‐active components may reduce IFT to a lower value. C₁₈=E₃ shows the best synergism with surface‐active components. However, the IFT values against pure crude oil are obviously higher than those against hydrocarbons, which may be caused by the nature of heavy oil.     

岔30断块S/P二元复合驱实验研究

针对华北岔30断块90℃高温、地层水矿化度18765.1 mg/L的特点,筛选得到了石油磺酸盐CDS-1与疏水缔合聚合物HNT201-3二元复合体系。0.05%CDS-1/HNT201-3二元复合体系与原油的界面张力可降到10^-2mN/m数量级;当HNT201-3浓度为1250mg/L时,复合体系的表观粘度为23.7 mPa.s。非均质岩心（模拟油层非均质变异系数和平均空气渗透率）驱油试验结果表明,注入驱油体系0.3PV、后续保护段塞0.1PV（聚合物HNT201-3浓度1250mg/L）时,可比水驱提高采收率19.73%OOIP。