苄基取代甜菜碱对聚四氟乙烯表面润湿性的影响

利用座滴法研究了两性离子表面活性剂苄基取代烷基羧基甜菜碱(BCB)和苄基取代烷基磺基甜菜碱(BSB)在聚四氟乙烯(PTFE)表面上的润湿性质,考察了表面活性剂浓度对接触角的影响趋势,并讨论了粘附张力、固-液界面张力和粘附功的变化规律.研究发现,在低浓度时,表面活性剂通过疏水作用吸附到PTFE表面,疏水链苄基取代支链化使其在固-液界面上的吸附明显低于气-液界面,接触角在很大的范围内保持不变.当体相浓度增加到大于临界胶束浓度(cmc)时, BCB和BSB分子在固-液界面上继续吸附,分子逐渐直立,造成PTFE-液体之间的界面张力(γ_SL)进一步降低,表面亲水性增加,接触角随浓度增加明显降低;另一方面, BSB由于具有较大的极性头,在高浓度时空间阻碍作用明显,导致其对PTFE表面润湿性改变程度小于BCB.     

支链化阳离子和甜菜碱表面活性剂对聚四氟乙烯表面润湿性的影响

利用座滴法研究了支链化阳离子表面活性剂十六烷基羟丙基氯化铵(C₁₆GPC)和两性离子表面活性剂十六烷基羧酸甜菜碱(C₁₆GPB)在聚四氟乙烯(PTFE)表面上的吸附机制和润湿性质, 考察了表面活性剂浓度对表面张力、接触角、粘附张力、固液界面张力和粘附功的影响趋势. 研究发现, 低浓度条件下, 表面活性剂疏水支链的多个亚甲基基团与PTFE表面发生相互作用, 分子以平躺的方式吸附到固体界面; 支链化表面活性剂形成胶束的阻碍较大, 浓度大于临界胶束浓度(cmc)时, C₁₆GPC和C₁₆GPB分子在固液界面上继续吸附, 与PTFE作用的亚甲基基团减少, 分子逐渐直立, 固液界面自由能(γ_sl)明显降低. 对于支链化的阳离子和甜菜碱分子, 接触角均在浓度高于cmc后大幅度降低.     

Gemini表面活性剂对疏水缔合聚丙烯酰胺界面吸附膜扩张流变性质的影响

采用小幅低频振荡和界面张力弛豫技术, 考察了疏水缔合水溶性聚丙烯酰胺(HMPAM)在正癸烷-水界面上的扩张黏弹性质, 研究了不对称Gemini表面活性剂C₁₂COONa-p-C₉SO₃Na对其界面扩张性质的影响. 研究发现, 疏水链段的存在, 使HMPAM在界面层中具有较快的弛豫过程, 扩张弹性显示出明显的频率依赖性. 表面活性剂分子可以通过疏水相互作用与聚合物的疏水嵌段在界面上形成类似于混合胶束的特殊聚集体. 表面活性剂分子与界面聚集体之间存在快速交换过程, 可以大大降低聚合物的扩张弹性. 同时, 聚合物分子链能够削弱表面活性剂分子长烷基链之间的强相互作用, 导致混合吸附膜的扩张弹性远低于单独表面活性剂吸附膜.     

不同结构烷基苯磺酸盐油水界面扩张粘弹性质

研究了2-甲基-5-(1-庚基辛基)苯磺酸钠、辛基苯磺酸钠和十六烷基苯磺酸钠在正辛烷-水界面上的扩张粘弹性质, 考察了链长变化和疏水基支链化对分子界面行为的影响. 研究结果表明, 链长增加导致分子间相互作用增强, 弹性增大; 疏水支链在界面上可能由于缠绕和变形产生界面慢弛豫过程, 导致较高的扩张模量.     

表面活性剂疏水链长对高温下泡沫稳定性的影响

选用不同疏水链长的α-烯烃磺酸盐(AOS)形成泡沫, 分别用泡沫衰减法和泡沫岩芯封堵法测定不同温度下的泡沫稳定性, 并采用动态表面张力、界面流变、分子模拟等方法研究了表面活性剂在气/液界面的吸附行为和界面吸附层的性质, 分析了高温下泡沫的稳定机制. 实验结果表明, 在高温下, 极性头的“锚定作用”减弱, 表面活性剂疏水链难以在气液界面保持以直立状态吸附, 疏水链碳数大于20的表面活性剂分子难以分立吸附, 其疏水链相互交叉缠绕, 增强了泡沫膜的强度, 减缓了气体通过液膜的扩散, 形成的泡沫在高温下具有较好的稳定性.     

均聚物/两嵌段共聚物/均聚物三元聚合物共混体系界面性质的Monte Carlo模拟

利用格子Monte Carlo(MC)模拟方法研究了两嵌段共聚物增容剂AB的链长及浓度对不相容性均聚物A/B共混体系界面性质的影响.研究结果表明,当两嵌段共聚物的体积分数φC=0.05时,随着两嵌段共聚物分子链长NC从10增至20,界面厚度剧烈减小,而当两嵌段共聚物的分子链长NC进一步增加到60时,界面厚度轻微增加;两嵌段共聚物的取向参数q随着分子链长的增长而增加,即共聚物分子在垂直界面方向的拉伸程度增大.当两嵌段共聚物AB的分子链长NC固定为10时,随着链浓度增大,界面厚度增加,共聚物分子链取向参数q减小,共聚物分子在垂直界面方向的拉伸程度减小.     

光敏季铵盐Gemini表面活性剂a4-6-m在气/液界面的吸附

合成了3种不对称结构的季铵盐Gemini表面活性剂a4-6-m, 分子的一根疏水链是偶氮苯为端基的4个亚甲基链, 另一根是不同长度的脂肪链(m=12, 14, 16). 研究结果表明, 反式偶氮苯封端的a4-6-m在气/液界面上以直立方式排列, 偶氮苯端基间的π-π相互作用导致吸附分子较为紧密地排列, 但吸附层外表面含有偶氮苯成分使临界胶束浓度(cmc)时的表面张力(γcmc)较大. 紫外光激发使反式结构偶氮苯变为顺式结构, 这些极性较强的顺式偶氮苯夹杂在直立的烷烃链间, 增强的偶极-偶极相互作用促进了分子紧密排列, 使分子占据面积(Amin)略微减小. 增长脂肪链长度有助于降低临界胶团浓度和C20(使水的表面张力降低20 mN·m-1时所需的表面活性剂浓度), 但对γcmc影响不大.     

1-(2-羟乙基)-2-烷基-咪唑啉缓蚀剂缓蚀机理的理论研究

采用量子化学计算、分子动力学模拟和分子力学相结合的方法, 对6种不同烷基链长的1-(2-羟乙基)-2-烷基-咪唑啉缓蚀剂抑制H2S腐蚀的缓蚀机理进行研究, 并对其缓蚀性能进行评价. 前线轨道分布和Fukui指数表明, 6种缓蚀剂分子的反应活性区域均集中在分子的咪唑环上, 3个反应活性中心分别位于咪唑环上的N(4), N(7)和C(8)原子, 可使咪唑环在金属表面形成多中心吸附. 分子的反应活性及活性区域分布对烷基链长并不敏感. 单分子吸附能、膜的内聚能、吸附角和链间距的计算数据显示, 缓蚀剂膜的稳定性以及膜与金属基体的结合强度随链长的增加而增大; 当正构烷基碳链长度大于13时, 缓蚀剂可在金属表面形成一层高覆盖度、致密的疏水膜, 能有效阻碍溶液中的腐蚀介质向金属表面扩散, 从而达到阻碍或延缓腐蚀的目的.     

PEO-PPO聚醚嵌段共聚物的表面活性及其在溶液界面的结构

利用和频振动光谱及表面张力测定技术对两亲性聚氧乙烯-聚氧丙烯(PEO-PPO)表面活性剂的表面活性及溶液界面结构进行了研究。结果表明:疏水PPO链段在溶液界面吸附并紧密排列是溶液表面张力降低的主要原因。增加溶液浓度、增大共聚物链内PPO与PEO聚合度比值可增加高分子链在界面的吸附,并使PPO在界面紧密排列,侧基(甲基)有序取向。另外,PPO在分子链中的位置也对这一行为产生影响,PPO位于分子链两端时的结构更有利于PPO在表面紧密堆积,降低界面高分子链间相互作用,减小溶液表面张力。     

三取代直链烷基苯磺酸钠的界面扩张性质

利用悬挂滴方法研究了五种表面活性剂3,4-二己基苯磺酸钠(66)、3,4-二庚基苯磺酸钠(77)、2-乙基-4,5-二己基苯磺酸钠(266)、2-丙基-4,5-二己基苯磺酸钠(366)和2-丁基-4,5-二己基苯磺酸钠(466)在空气-水和癸烷-水界面上的扩张流变性质,考察了烷基取代在苯环不同位置对分子界面行为的影响.研究发现,苯环不同位置的取代烷基链长变化对扩张弹性模量和扩张粘性模量影响不同.随着烷基链长增长,表面扩张弹性模量均增加,而扩张粘性模量表现则不同:邻位短链烷基碳数从2变化到4,对粘性模量贡献不大;而间位长链烷基增长对表面弛豫过程影响较大,粘性模量明显增大.油分子的插入能大大削弱间位长链烷基间的强相互作用,一方面导致界面弹性模量和粘性模量远低于表面,同时使得同分异构分子77和266的界面扩张粘性模量数值接近.     

Dilational Rheological Properties of Non-Ionic Surfactants at the Water–Decane Interface: Effect of Unsaturated Hydrophobic Group

The interfacial tensions and dilational properties of adsorbed films of two non-ionic surfactants with different hydrophobic groups, polyoxy-ethylene sorbitan stearate (Tween 60) and polyoxy-ethylene sorbitan monooleate (Tween 80), at the water–decane interface have been investigated by the drop-shape analysis method. The effects of dilational frequency and bulk concentration on the interfacial properties were expounded. The influence of low temperature on the interfacial tensions and dilational properties have also been researched. The experiment results show that the interfacial activity of Tween 80 is rather large compared with Tween 60. The minimum area per molecule at the water–decane interface (A_min) value of Tween 80 is little large than that of Tween 60, which is due to the steric effect of unsaturated double bond in Tween 80 molecule. The dilational data show that the ethylene oxide groups of non-ionic surfactant form a stable sub-layer, which results in the increase of modulus and the decrease of phase angle for both Tween 60 and Tween 80 than those of common ionic surfactants. Moreover, the unsaturated hydrophobic group of Tween 80 is much flexible, which is easily crosslinked and entangled. Therefore, dilational modulus of Tween 80 is higher and phase angle is lower than that of Tween 60. Low temperature decreases the flexibility of unsaturated hydrophobic group and lessens the influence on the interaction of saturated hydrophobic group. Saturated surfactant molecules of Tween 60 almost lose temperature response.     

界面张力弛豫法研究不同结构破乳剂油水界面扩张粘弹性

采用界面张力弛豫法研究了支链破乳剂AE121和直链破乳剂SP169在正癸烷-水界面上的扩张粘弹性质，并与小幅周期振荡法获得的结果进行了比较.阐述了两种破乳剂的扩张模量随扩张频率和破乳剂浓度的变化规律.研究发现，在低频率处，两种破乳剂的扩张模量均接近于零；在中间频率范围内，扩张模量随扩张频率的增加而增大；在高频率处，扩张模量的幅度接近于极限扩张弹性.在中间频率范围内，扩张模量随破乳剂浓度增大，在接近临界胶束浓度处出现一个极大值；同时还发现，界面上和界面附近的微观弛豫过程的数目随破乳剂浓度增加而增大，其贡献也呈规律性变化.     

Adsorption and Aggregation Properties of Some Polysorbates at Different Temperatures

Measurements of the surface tension of aqueous solutions of polysorbates (Tween 20, Tween 60 and Tween 80) at 293, 303 and 313 K were made. On the basis of the obtained results the Gibbs surface excess concentration of the Tweens at the water–air interface and critical micelle concentrations were determined. Knowing the Gibbs surface excess concentration and taking into account the difference between the limiting area occupied by water and Tween molecules at the water–air interface, the fraction occupied by Tween molecules was established. The limiting area occupied by the Tween molecule was calculated by applying the Joos equation. The area determined in such a way was confirmed by the calculations of cross section of Tween molecules based on the bond lengths and the angles between them as well as the average distance between the molecules, taking into account their different conformations. This area was used for calculation of the standard Gibbs energy of adsorption using the Langmuir equation. The standard Gibbs energy of Tweens adsorption at the water–air interface was also calculated from the hydrophobic part of Tween molecule–water interface tension and that of hydrophobic part. Using the determined values of standard Gibbs energy of adsorption at different temperatures, the standard enthalpy and entropy values were deduced. The standard thermodynamic functions of micellization were also determined and compared to the Gibbs energy of Tween molecules interactions through the water phase.     

Friction and adsorption of aqueous polyoxyethylene (Tween) surfactants at hydrophobic surfaces

The nanotribological responses of a series of nonionic polyoxyethylene surfactants (Tween 20, Tween 40, Tween 60, and Tween 80) were investigated after they were adsorbed from aqueous solution onto atomically smooth hydrophobic substrates. The hydrophobic surfaces were composed of a condensed monolayer of octadecyltriethoxysilane (OTE; contact angle theta>110 degrees ). The nanorheological measurements were performed using a modified surface forces apparatus after coating atomically smooth mica with these OTE monolayers, while adsorption measurements were performed using phase-modulated ellipsometry on silicon wafers coated with these same monolayers. The minimum surface-surface separation observed under high load in friction studies agreed quantitatively with the thickness obtained from ellipsometry. For Tweens 20, 40, and 60, the thickness of the adsorbed film increases with increasing alkyl chain length. Systematic investigations of the nanorheological response showed that there is a "solid-like" elastic response from confined surfactant layers, which is the case for the smallest separations to separations up to slightly larger than twice the adsorbed film thickness. In kinetic friction, these confined layers are characterized by a shear stress of approximately 3 MPa with minimal dependence on shear rate. The magnitude of the sliding shear stress is the same as the apparent yield stress at approximately 3 MPa; it is independent of alkyl chain length within the Tween family of surfactants and corresponds to a nominal friction coefficient of mu approximately 1. A similar friction coefficient is observed for boundary lubrication on the macroscopic scale in a tribometer utilizing hydrophobic surfaces and mu approximately 1.1 for Tweens 20, 40, and 60. These results suggest that while Tween molecules adsorb onto hydrophobic surfaces to form a robust separating layer, the lubricating properties of these layers are dominated by a highly dissipative slip plane, the same for all alkyl chain lengths.     

Interfacial Dilational Properties of Hydrophobically Modified Partly Hydrolyzed Polyacrylamide and Anionic Surfactants at the Water-Decane Interface

The dilational viscoelastic properties of hydrophobically modified partly hydrolyzed polyacrylamide and anionic surfactants (4,5-diheptyl-2-propylbenzene sulfonate and gemini surfactant C₁₂COONa-p-C₉SO₃Na) in the absence or presence of electrolyte have been investigated at the decane–water interface by means of longitudinal method and the interfacial tension relaxation method. Experimental results show that at low surfactant concentration, the increase of the dilational modulus by the addition of surfactant molecules at low frequency might be explained by the mix-adsorption of the polymer chains and surfactant molecules. At the same time, polymer chain could sharply decrease the dilational modulus of surfactant film mainly due to the weakening of the strong interactions among long alkyl chains in surfactant molecules. At high surfactant concentration, the addition of surfactant molecules can decrease the dilational modulus of polymer solution due to the fast process involving in the exchange of surfactant molecules between the interface and the mixed complex formed by surfactant molecules and hydrophobic micro-domains. The added electrolyte, which results in screening of electrostatic interactions between the ionized groups, generally increases the frequency dependence of the interfacial dilational modulus. The data obtained on the relaxation processes via interfacial tension relaxation measurements can explain the results from oscillating barriers measurements very well.     

疏水改性聚丙烯酰胺对原油组分界面扩张流变性质的影响

利用悬挂滴方法研究了疏水改性聚丙烯酰胺(HMPAM)对胜利采油厂高温高盐油藏采出原油中酸性活性组分和沥青质界面膜扩张流变性质的影响,考察了不同活性组分浓度条件下的界面扩张流变行为.实验结果表明:1750mg·L-1HMPAM能够在界面上形成网络结构,界面扩张模量数值高达100mN·m-1左右;油相中的酸性组分随着老化时间增加吸附到界面上,与HMPAM分子的疏水改性部分形成聚集结构,一方面通过快速的扩散交换过程大大降低扩张模量,另一方面通过与疏水改性部分的相互作用加强HMPAM分子间的缔合强度,增强网络结构的弹性.沥青质分子尺寸相对较大,分子间存在氢键等较强的相互作用,造成沥青质界面聚集体和HMPAM形成的网络结构共同决定界面膜性质,混合膜的扩张模量较单独HMPAM体系仅略有降低.     

The interfacial dilational properties of hydrophobically modified associating polyacrylamide studied by the interfacial tension relaxation method at an oil-water interface

The interfacial dilational viscoelastic properties of hydrophobically associating block copolymer composed of acrylamide (AM) and a low amount of 2-phenoxylethyl acrylate (POEA) (<1.0 mol%) at the octane-water interfaces were studied by means of the interfacial tension relaxation method. The dependencies of interfacial dilational elasticity and viscous component on the dilational frequency were investigated. The interaction of hydrophobically associating block copolymer [P(AM/POEA)] with sodium dodecyl sulfate (SDS) has been explored. The results show that at lower frequency, the dilational elasticity for different concentration copolymer is close to zero; at higher frequency, the dilational elasticity shows no change with increased frequency; At moderate frequency (10(-3)-1 Hz), the dilational elasticity decreased with a decrease in the dilational frequency. The results show that the hydrophobic groups of [P(AM/POEA)] chains can be associated by inter- or intrachain liaisons in water solution. The dilational viscous component for P(AM/POEA) comes forth a different maximum value at different frequencies when the polymer concentration is different. It is generally believed that the dilational viscous component reflects the summation of the various microscopic relaxation processes at and near the interface and different relaxation processes have different characteristic frequencies. The spectrum of dilational viscous component may appear more than once maximum values at different frequencies. The influence of SDS on the limiting dilational elasticity and viscous component for polymer solution was elucidated. For 5000 ppm polymer solution, the limiting dilational elasticity decreased with an increase in SDS concentration. The dilational viscous component passed through a maximum value with a rise in the dilational frequency, which appeared at different frequency when SDS concentration is different; and the higher is the concentration, the lower is the dilational frequency. It can be explained that macromolecules may be substituted by SDS molecules in the interface and the interaction of molecules decrease, which makes the limiting dilational elasticity decrease. For 200 ppm polymer solution, the limiting dilational elasticity increased firstly and then decreased with SDS concentration increasing. This may be explained that the interfacial polymer concentration is so low that SDS molecules absorbed in the interface dominate dilational properties of the interfacial film even at very low SDS concentration. However, SDS molecules can gradually substitute the polymer molecules in the interface with a rise in SDS concentration, which results in the decrease in the limiting dilational elasticity.     

A study of interfacial dilational properties of two different structure demulsifiers at oil-water interfaces

The interfacial dilational viscoelastic properties of two demulsifiers with straight chain (SP-169) and branched chain (AE-121) at the oil-water interfaces were investigated by means of the longitudinal waves method and the interfacial tension relaxation method, respectively. The results obtained by the longitudinal waves method showed that the dilational viscous component for AE-121 and SP-169 also passed through a maximum value with increasing concentration. It was found that the maximum value appeared at different demulsifier concentrations during our experiment frequency; and the higher is the dilational frequency, the lower is the concentration. The influences of AE-121 and SP-169 on the dilational viscoelastic properties of the oil-water interface containing surface-active fraction from Iranian crude oil have been measured. The results clearly stated that both demulsifiers could obviously decrease the dilational elasticity of oil-water interface containing surface-active fraction. At low concentration, because of stronger adsorption ability, SP-169 has stronger ability to decreasing the dilational modulus than AE-121. We also found that the dilational modulus of the interface contained surface-active fraction passed through a minimum value with increasing demulsifier concentration for both demulsifiers. This result indicated the dosage of demulsifier had an optimum value. The results obtained by means of interfacial tension relaxation method showed that the slow relaxation processes involve mainly rearrangement in the conformation of the molecules appeared with increasing demulsifier concentration.