X型与线型嵌段聚醚在空气/水和正庚烷/水界面上聚集行为的比较研究

通过阴离子聚合方法合成了环氧乙烷(EO)含量和分子量均相同的线型聚氧丙烯(PEO)-聚氧乙烯(PPO)(LPE)和X型聚氧丙烯-聚氧乙烯(TPE)嵌段聚醚,考察了它们在空气/水及正庚烷/水界面上聚集行为的差异.界面活性的研究结果表明,TPE降低水、正庚烷界面张力的效率和效能均低于LPE的.聚醚分子在正庚烷/水界面达到吸附平衡的时间比在空气/水表面短.由于正庚烷分子插入到聚醚吸附层中,聚醚分子可以在正庚烷/水界面上采取更为直立的状态,因此聚醚分子在正庚烷/水界面扩散较快.聚醚在正庚烷/水界面的扩张弹性高于空气/水表面的.     

支状嵌段聚醚的界面聚集行为及对原油乳状液的破乳作用

合成了三种不同聚氧丙烯/聚氧乙烯(PPO/PEO)比例的含苯环支状嵌段聚醚, 通过界面张力、界面流变、表面压以及对原油乳状液的破乳脱水效果的测定, 考察了其界面聚集行为和破乳作用对PEO含量和分子量的依赖性, 并且对比研究了三种支状聚醚分子交联前后的破乳性能. 结果表明, PEO含量高且分子量大者,其单分子界面占据面积大, 在油/水界面达到吸附平衡的时间短, 其油/水界面扩张模量及扩张弹性均高于PEO含量较少者. 但是对原油乳状液的破乳脱水效果则是PEO含量居中的聚醚最好. 温度影响和交联与否的研究表明, 交联并不能提高分子量较大的聚醚对原油乳状液的破乳效果, 温度对聚醚分子交联前后的破乳效果有不同的影响规律. 本研究可为原油集输过程中化学品的选择与应用提供一定的依据.     

聚醚类破乳剂的界面扩张流变性质

采用悬挂滴方法研究了不同结构聚醚类破乳剂与煤油间的界面张力及界面扩张流变性质. 结果表明, 4种聚醚类破乳剂均具有较强的降低界面张力能力, 且支链化程度越低分子在界面上排列越紧密, 直线型破乳剂在低浓度条件下界面张力最低. 破乳剂的分子尺寸较大, 慢弛豫过程控制界面膜性质, 吸附膜以弹性为主. 同时, 柔性聚氧乙烯链和聚氧丙烯链对界面膜性质的影响较大, 随着支链化程度增大, 界面分子间相互作用增强, 界面膜弹性增强, 黏性降低.     

吸附与润湿 Ⅱ.Triton X-100和Triton X-305在炭黑/水和炭黑/环己烷界面上的吸附层结构

(1)测定了15℃和30℃时炭黑自水和环己烷中吸附非离子型表面活性剂Triton X-100和Triton X-305的等温线;(2)计算了吸附过程的标准热力学函数△G~0、AH~0和△S~0;(3)测定了石墨/水/环己烷和石墨/水/空气的接触角与表面活性剂浓度的关系.分析所得结果,可得结论:在炭黑/水或石墨/水界面上,Triton型表面活性分子形成单分子吸附层,分子以憎水的iso-C_8H_(17)C_6H_4基团附着在表面,而以亲水的聚氧乙烯链伸入水相的方式取向;在炭黑/环己烷或石墨/环己烷界面上,分子是通过聚氧乙烯链吸附到表面上的,当浓度增加时分子在表面上可能通过聚氧乙烯链间的相互作用而发生聚集,即可能形成表面反式胶团.     

无机盐对支状嵌段聚醚破乳作用的影响

通过阴离子聚合反应合成了一种七支状聚氧丙烯/聚氧乙烯(PPO/PEO)三嵌段聚醚;考察了不同无机盐存在时对原油乳状液的破乳效果的影响;通过界面张力、浊点和界面膨胀流变性的测定探讨了其界面聚集行为和破乳作用对无机盐的依赖性.结果表明,盐溶型无机离子存在时,能提高聚醚的破乳效果,而盐析型无机离子存在时,不利于聚醚的破乳作用;温度升高破乳速度加快,但45℃时脱出的水质最清.     

吸附与润湿II.Triton X-100和Triton x-305在炭黑/水和炭黑/环己烷界面上的吸附层结构

测定了15℃和30℃时炭黑自水和环己烷中吸附非离子型表面活性剂TritonX-100和Triton X-305的等温线;计算了吸附过程的标准热力学函数;测定了石墨/水/环己烷和石墨/水/空气的接触角与表面活性剂浓度的关系, 分析所得结果,可得结论:在炭黑/水或石墨/水界面上,Triton型表面活性分子形成单分子吸附层,分子以憎水的iso-C8H17C6H4基团附着在表面,而以亲水的聚氧乙烯链伸入水相的方式取向;在炭黑/环已烷或石墨/环己烷界面上,分子是通过聚氧乙烯链吸附到表面上的,当浓度增加时分子在表面可能通过聚氧乙烯链间的相互作用而发生聚集,即可能形成表面反式胶团。     

薄层法研究十二烷基苯磺酸钠对硝基苯/水界面电子转移的影响

用薄层法研究了阴离子表面活性剂十二烷基苯磺酸钠(SDBS)对硝基苯/水界面电子转移的影响. 实验结果表明, 随着水相中十二烷基苯磺酸钠浓度的增加, 有机相中十甲基二茂铁(DMFc)和水相中Fe(CN)₆^3-发生的界面双分子反应的阴极平台电流呈现递减趋势, 但是界面双分子反应速率常数却呈递增趋势. 这是由于阴离子表面活性剂十二烷基苯磺酸钠在硝基苯/水界面形成了修饰层, 影响了界面双电层结构. SDBS在液/液界面的吸附为Langmuir吸附.     

吸附与润湿I非离子表面活性剂在SiO2/水和SiO2/环己烷界面的吸附层结构

根据Triton X-100在硅胶/水和硅胶/环己烷界面以及Triton x-305在硅胶/水界面的吸附结果,提出了两种简单的吸附模型,在硅胶/环己烷界面上形成的是单分子吸附层,吸附质分子以乙氧基链躺在硅胶表面上而以碳氢链伸入环己烷的方式取向.在硅胶/水界面上形成的是双分子吸附层,第一层中的分子以乙氧基链躺在硅胶表面上而以碳氢链朝外;第二层中的分子取向相反,即以碳氢链朝向第一层分子形成的碳氢链层,而以乙氧基链伸进水中,对石英玻璃-水-环己烷的接触角(θ水)的测定结果表明,θ水随水相中表面活性剂浓度的增加先升后降,进一步支持了上述吸附模型。     

油/水界面表面活性剂的复配协同机制

采用耗散颗粒动力学(DPD)方法模拟了椰油酸二乙醇酰胺(6501)分别与十二烷基-α-烯烃磺酸钠(DAOS)、椰油酰胺丙基二甲基甜菜碱(CAB)和十二烷基苯磺酸钠(SDBS)复配体系中表面活性剂在油/水界面的排布行为, 探讨了盐度及分子结构对单一和复配表面活性剂界面活性的影响, 从界面效率、界面密度和分子排布等角度讨论了油水界面表面活性剂混合体系的复配协同增效机制.     

十八烷基聚氧乙烯表面空间结构和蛋白质吸附行为研究

为探讨聚合物-水界面十八烷基聚氧乙烯链(SPEO)空间结构和白蛋白选择性吸附行为的内在联系,本文采用聚甲基丙烯酸甲酯接枝十八烷基聚氧乙烯(PMMA-g-SPEO),通过不同热处理方式获得了具有“环形链”(A)和“尾形链”(B)结构的两种模型表面.在A表面,水相接触角随水化时间的延长而迅速降低,最终亲水性的界面可同时有效阻抗白蛋白和纤维蛋白原的吸附,但不呈现对白蛋白的选择性吸附;而在B表面,水相接触角随水化时间的延长变化不大,最终疏水性的界面可在有效阻抗纤维蛋白原的吸附同时,有效诱导白蛋白的选择性吸附,具有聚氧乙烯(PEO)阻抗非特异性吸附和十八烷基选择性吸附协同作用的特点.     

Aggregation behavior of block polyethers with branched structure at air/water surface

The block polyethers with various branch structure, such as TEPA[(PO)₃₆(EO)₁₀₀]₇, TEPA[(PO)₃₆(EO)₁₀₀(PO)₃₆]₇, and TEPA[(PO)₃₆(EO)₁₀₀(PO)₅₆]₇ were synthesized. Moreover, the aggregation behavior was investigated via the measurements of equilibrium surface tension, dynamic surface tension, and surface dilational viscoelasticity, in order to probe the effect of the block structure on the property of the branched block polyethers. The surface tension results show that the efficiency and effectiveness of the block polyethers to lower surface tension increase with the increase of the PO group numbers. The maximum surface excess concentration (Γ_max) values and the minimum occupied area per molecule at the air/water interface (A_min) values of the branched block polyethers obtained from Gibbs adsorption equations increase and decrease with the increases of the PO group numbers, respectively. The dynamic parameters n and t^* representing the diffusion speed of the polyether molecules from bulky solution to the subsurface and from the subsurface to the air/water surface are obtained according to the equation proposed by Rosen. The results show that the n values firstly increase and then decrease and t^* values decrease with the increase of the polyether concentrations. The results of surface dilational viscoelasticity show that the dilational modulus of TEPA[(PO)₃₆(EO)₁₀₀(PO)₅₆]₇ is the largest among the three block copolymers at the low concentration (<1 mg L⁻¹) but that of TEPA[(PO)₃₆(EO)₁₀₀]₇ is the largest at the high concentration (>1 mg L⁻¹).     

Spreading of oil from protein stabilised emulsions at air/water interfaces

Spreading of a drop of an emulsion made with milk proteins on air/water interfaces was studied. From an unheated emulsion, all oil molecules could spread onto the air/water interface, indicating that the protein layers around the oil globules in the emulsion droplet were not coherent enough to withstand the forces involved in spreading. Heat treatment (90 °C) of emulsions made with whey protein concentrate (WPC) or skim milk powder reduced the spreadability, probably because polymerisation of whey protein at the oil/water interface increased the coherence of the protein layer. Heat treatment of emulsions made with WPC and monoglycerides did not reduce spreadability, presumably because the presence of the monoglycerides at the oil/water interface prevented a substantial increase of coherence of the protein layer. Heat treatment of caseinate-stabilised emulsions had no effect on the spreadability. If proteins were already present at the air/water interface, oil did not spread if the surface tension (γ) was <60 mN/m. We introduced a new method to measure the rate at which oil molecules spread from the oil globules in the emulsion droplet by monitoring changes in γ at various positions in a ‘trough’. The spreading rates observed for the various systems agree very well with the values predicted by the theory. Spreading from oil globules in a drop of emulsion was faster than spreading from a single oil drop, possibly due to the greater surface tension gradient between the oil globule and the air/water interface or to the increased oil surface area. Heat treatment of an emulsion made with WPC did not affect the spreading rate. The method was not suitable for measuring the spreading rate at interfaces where surface active material is already present, because changes in γ then were caused by compression of the interfacial layer rather than by the spreading oil.     

Influence of Surfactants Synergism on the Adsorption Behavior at Air/Water and Solid/Water Interfaces

The influence of synergistic interaction between sodium dodecylsulfate (SDS) and N,N-dimethyldodecan-1-amine oxide (DDAO) on their adsorption at air/water and solid/water interfaces at 20°C is investigated. The critical micelle concentration values obtained from surface tension measurements indicated strong synergism between SDS and DDAO, according to regular solution model. The excess surface concentration (Γ) and the minimum occupied area by single and mixed surfactant monomers (A_min) at liquid/air interface were also calculated. The adsorption onto the activated charcoal and silica was then measured to find out the correlation between surfactant synergism and their adsorption at solid/water interface. The amounts of surfactant adsorbed onto 1 wt% activated charcoal follow the trend: SDS/DDAO > DDAO > SDS. SDS molecules do not adsorb onto 5 wt% silica substrate, while SDS/DDAO mixed system was found to have the highest adsorption behavior. The obtained indicate that SDS can be removed from water by mixing it with amphoteric surfactant.     

Effect of inorganic salts on the aggregation behavior of branched block polyether at air/water and n-heptane/water interfaces

The effect of inorganic salts (CaCl₂, MgCl₂, NaCl, NaI and NaSCN) on the aggregation behavior of a synthesized polyether with seven poly (ethylene oxide)-b-poly (propylene oxide)-b-poly (ethylene oxide) (PEO-PPO-PEO) arms attached to a tetraethylenepentamine core (simplified AE73) at air/water and n-heptane/water interfaces has been investigated by interfacial tension and oscillating bubble methods. The additions of NaCl, CaCl₂, and MgCl₂ may facilitate the micellization of AE73 and increase its maximum interfacial excess concentration (Γ_max) due to the “salting out” effect, while NaSCN induces opposite effect and NaI exerts little influence. The adsorption kinetics of AE73 is controlled not only by the diffusion between the bulk solution and the interfacial layer but also by the energetic and steric barriers generated by the already adsorbed molecules. The adsorption relaxation time of AE73 is reduced with the addition of salts and this phenomenon is more prominent at the n-heptane/water interface. The “salting in” ions decrease the dilational modulus of AE73 while the “salting out” ions induce an opposite effect. The mechanisms of the interaction between inorganic ions and the polyether were discussed; the difference in aggregation behavior between linear and branched block polyethers were also compared.     

Synthesis and evaluation of demulsifiers with polyethyleneimine as accepter for treating crude oil emulsions

Demulsifiers provide an important means of breaking water‐in‐crude oil, which are formed during crude oil exploitation. In present work, twenty polyether copolymers based on polyethyleneimine (PEI) were synthesized. The interfacial properties of the PEI polyethers at the water‐crude oil interface were described by interfacial tension (IFT) and interfacial dilational modulus. The effects of position isomerism, size of intermediate and ratio of ethylene oxide (EO)/propylene oxide (PO) on the demulsification efficiency of these polyethers were studied. The results show that different positions of the EO and PO in copolymers lead to huge difference in both interfacial properties and demulsification performance. Polymers with hydrophilic core and hydrophobic tails (Ex‐mn series) are not efficient on demulsification of water‐in‐oil emulsion whereas polymers with hydrophobic core and hydrophilic tails (Px‐mn series) are. Meanwhile, Px‐mn series show higher IFT and lower interfacial dilational modulus than Ex‐mn series. In the same series, the IFT and interfacial dilational modulus decrease with decreasing EO/PO ratio. In the series with best demulsification performance (P199‐mn series), 60 min water removal rates of the polymers increase with decreasing EO/PO ratio at 65°C. In other words, the longer the hydrophobic blocks of polymers, the stronger the demulsification capacity. The effect of concentration of demulsifier on the demulsification efficiency was also investigated. Copyright © 2015 John Wiley & Sons, Ltd.     

Interfacial tension and wetting behavior of air/oil/ionic liquid systems

We measured the interfacial tension and the density of air/n-hexane, n-decane, 1-perfluorohexane/1-hexyl-3-methyl-imidazolium hexafluorophosphate systems as a function of temperature. From the air/ionic liquid surface tension values, it was suggested that Coulombic interaction between imidazolium cations and counter anions are not so much different between the surface and bulk. The density values indicated that the decrease of surface tension by saturating organics was closely correlated to the mutual solubility between ionic liquid and organics. Interfacial tension at the oil/ionic liquid interfaces suggested that ionic liquid molecules were more ordered at the oil/ionic liquid interfaces compared to the air/ionic liquid interfaces, but the decrease of the entropy due to the interfacial orientation of ionic liquid was compensated by the increase of the entropy due to the contact of different chemical species. The initial spreading coefficients and the Hamaker constants indicated that all the oil phases spread at the air/ionic liquid interfaces spontaneously, and form the complete wetting films.     

Dynamics of protein and mixed protein/surfactant adsorption layers at the water/fluid interface

The adsorption behaviour of proteins and systems mixed with surfactants of different nature is described. In the absence of surfactants the proteins mainly adsorb in a diffusion controlled manner. Due to lack of quantitative models the experimental results are discussed partly qualitatively. There are different types of interaction between proteins and surfactant molecules. These interactions lead to protein/surfactant complexes the surface activity and conformation of which are different from those of the pure protein. Complexes formed with ionic surfactants via electrostatic interaction have usually a higher surface activity, which becomes evident from the more than additive surface pressure increase. The presence of only small amounts of ionic surfactants can significantly modify the structure of adsorbed proteins. With increasing amounts of ionic surfactants, however, an opposite effect is reached as due to hydrophobic interaction and the complexes become less surface active and can be displaced from the interface due to competitive adsorption. In the presence of non-ionic surfactants the adsorption layer is mainly formed by competitive adsorption between the compounds and the only interaction is of hydrophobic nature. Such complexes are typically less surface active than the pure protein. From a certain surfactant concentration of the interface is covered almost exclusively by the non-ionic surfactant. Mixed layers of proteins and lipids formed by penetration at the water/air or by competitive adsorption at the water/chloroform interface are formed such that at a certain pressure the components start to separate. Using Brewster angle microscopy in penetration experiments of proteins into lipid monolayers this interfacial separation can be visualised. A brief comparison of the protein adsorption at the water/air and water/n-tetradecane shows that the adsorbed amount at the water/oil interface is much stronger and the change in interfacial tension much larger than at the water/air interface. Also some experimental data on the dilational elasticity of proteins at both interfaces measured by a transient relaxation technique are discussed on the basis of the derived thermodynamic model. As a fast developing field of application the use of surface tensiometry and rheometry of mixed protein/surfactant mixed layers is demonstrated as a new tool in the diagnostics of various diseases and for monitoring the progress of therapies.     

Native and Hydrophobically Modified Human Immunoglobulin G at the Air/Water Interface

The adsorption of human immunoglobulin G (IgG) at the air/water interface was monitored both by the in situ radiotracer technique using [(14)C] labeled IgG and by surface tension measurements. The results reveal that adsorption of IgG from single protein systems displays bimodality due to molecular rearrangements at the interface. Above the threshold value of 1.5x10(-2) mg/ml solution concentration, adsorbed IgG molecules reoriented from the side-on to the end-on configuration. The existence of a lag time which did not appear in Gamma=f(t) curves, was observed in Pi=f(t) relationships at low protein concentrations and was due to the limits of the surface pressure technique to detect protein adsorption. The adsorption of native IgG was also carried out in the presence of a hydrophobized IgG obtained by grafting capryloyl residues to its lysine groups by reaction with N-hydroxysuccinimide ester of caprylic acid, which yielded 19 covalently bound alkyl chains to the IgG molecule (19C(8)-IgG). This modified IgG exhibited enhanced adsorption at the air/water interface, as manifested by its increased adsorption efficiency relative to the native protein. Sequential and competitive adsorption experiments from binary mixtures of native IgG and 19C(8)-IgG clearly demonstrate that the displacement of the native protein from the air/water interface strongly depended on the manner of how 19C(8)-IgG and native IgG competed with each other. When the two proteins competed simultaneously, 19C(8)-IgG predominantly occupied the available area but when native IgG was adsorbed first, for 2 h, the sequentially adsorbed 19C(8)-IgG was incapable of substantially displacing it from the interface. Copyright 2001 Academic Press.     

Partition and water/oil adsorption of some surfactants

Adsorption isotherms have been determined at the water/oil interface for five biphasic systems involving surfactants (non-ionic and ionic) present in both phases at partition equilibrium. The systems studied were polyoxyethylene(23)lauryl ether (Brij35) in water/hexane and four ionic surfactants, hexadecyltrimethylammonium bromide (CTAB), and a series of three tetraalkylammonium dodecylsulfate (TEADS, TPADS, and TBADS) in water/CH 2Cl 2. Interfacial tension measurements performed at the water/air and water/oil interfaces provided all the necessary information for the determination of the adsorption parameters by taking partition into account. These measurements also allowed the comparison of the adsorption properties at both interfaces which showed an increase of the adsorption equilibrium constant and a decrease of the maximum surface concentration at the water/oil interface compared to water/air. The values of the critical aggregation concentration showed, in all cases, that only the surfactant dissolved in the aqueous phase contribute to the decrease of the water/oil interfacial tension. In the case of the four ionic surfactants, the critical aggregation concentration obtained in biphasic conditions were lowered because of the formation of mixed surfactant-CH 2Cl 2 aggregates.