正负离子表面活性剂与非离子表面活性剂混合水溶液的相互作用

非离子表面活性剂的加溶作用有助于正负离子表面活性剂的溶解,在恰当比例时,能基本保持其表面活性;正负离子表面活性剂与非离子表面活性剂之间的相互作用很弱,容易形成接近“理想”的混合胶团;恒定非离子表面活性剂浓度时,随正负离子表面活性剂浓度增加,溶液的浊点也增加;超过临界胶团浓度后浊点下降。     

Calorimetric and Scattering Studies on Micellization of Pluronics in Aqueous Solutions: Effect of the Size of Hydrophilic PEO End Blocks,Temperature, and Added Salt

Micellar behavior of five ethylene oxide–propylene oxide (EO–PO) triblock copolymers, called Pluronics, with similar molecular weights of middle block PPO (～2250 g/mol) and varied percentages of poly(ethylene oxide) (10%, 40%, 50%, 70%, and 80%, referred to as L81, P84, P85, F87, and F88, respectively) was examined by thermal (isothermal titration calorimetry and high-sensitivity differential scanning calorimetry), spectral (UV–vis), and dynamic light scattering (DLS) techniques. Micellization was decreased with increasing hydrophilicity of copolymer but induced in the presence of salt. Critical micelle temperatures (CMTs) of copolymers at different concentrations, with and without sodium chloride, are reported. Viscosity and DLS results reveal that highly hydrophilic copolymers (F87 and F88) did not show significant change in micelle size even at temperatures close to cloud point, whereas micelle growth and sphere-to-rod transition occurred for P84 and P85. Surface tension of solutions in water and salt also show enhanced surface activity and salt-induced micellization. The CMTs for different systems using different methods are compared.     

Effect of pH on the Behavior of Hyaluronic Acid in Dilute and Semidilute Aqueous Solutions

Summary : Viscosity, asymmetric flow field-flow fractionation (AFFFF) methods, and dynamic light scattering (DLS) experiments were used to characterize the effect of pH on the behavior of dilute and semidilute aqueous buffered solutions of hyaluronic acid (HA). It is shown that degradation of HA occurs at pH < 4 and pH > 11, and in the domain 4 < pH < 11 virtually no disruption of the HA chains occurs. The pH-induced scission of HA is attributed to the cleavage of glycosidic bonds. In dilute solutions, intramolecular rupture of HA chains occurs and in the semidilute concentration regime network-fragmentation is observed at low and high pH values. The degree of degradation of HA is most marked at high pH. From the molecular weight and radius of gyration obtained from AFFFF at different pH values, it is clear that the degradation of HA starts at early times after preparation of the solution, and continues for a couple of days. The kinetics of degradation of HA is fastest at high pH.     

Micellization and Effect of Salt Behavior on Meristyl Alcohol Based Bis-Sulfosuccinate Gemini Surfactants in Aqueous Solutions

A series of bis-sulfosuccinate anionic gemini surfactants were synthesized from meristyl alcohol (BSGSMA_1,4; BSGSMA_1,6, and BSGSMA_1,8) containing 4, 6, and 8 methylene chains as different flexible spacer lengths. The chemical structures of synthesized geminis were confirmed by using spectroscopic analytical techniques, viz., elemental analysis, Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance spectroscopy(NMR). Investigations were carried out to examine the effect of different spacer length and different salts (organic and inorganic) on surface and fluorescence properties of prepared gemini surfactants. The results of surface properties shown that surface tension at CMC (?_CMC) and critical micelle concentration (CMC) were reduced and pC₂₀ value was enhanced with increased spacer length. Fluorescence investigations were also revealed the significance of longer spacer with the concluded remarks of higher aggregation number and reduced micropolarity for BSGSMA_1,8 having elongated flexible spacer. The results of salts studies had shown the better results for organic salts as compared to inorganic salts.     

Aggregation Behavior of Titanium Dioxide Nanoparticles in Aqueous Environments

We report on the stability of titanium dioxide nanoparticles suspended in various aqueous solutions with and without the presence of a model organic contaminant—salicylic acid. The stability of the suspended nanoparticles was revealed by measuring the isoelectric point by means of zetapotential scans and measuring the growth kinetics of the hydrodynamic particle size by means of dynamic light scattering (DLS) under different pH conditions. Aggregated nanoparticle sizes were also examined using atomic force microscopy. It was found that salicylic acid had a dramatic impact on the aggregation behavior of TiO₂ nanoparticles, suggesting that salicylic acid adsorbs to TiO₂ nanoparticles surfaces.     

Rheological Behavior and Scattering Studies of Acrylamide-Based Copolymer Solutions

Summary: In this paper the chemical structure of an acrylamide-N,N-dihexylacrylamide copolymer was established by IR and NMR. Static and dynamic light scattering in formamide were used in order to evaluate the polymer structural parameters, such as weight-average molecular weight (M_w), second virial coefficient (A₂), radius of gyration (R_G), the form factor P(q) and the hydrodynamic radius (R_H). Additionally to the classical characterization, those results indicated the presence of aggregation, showing that formamide is not a very good solvent, as stated in earlier investigations. The rheological behavior in aqueous solutions was evaluated as a function of the salt concentration. The solutions presented an important viscosity increase in the presence of NaCl and did not show any sensitivity to the presence of CaCl₂. This result is in favor of the oil recovery especially in high salinity reservoirs.     

动态光散射法研究季铵盐Gemini表面活性剂的胶团化行为

用动态光散射技术在10～70℃温度范围内,通过测定胶团的平均流体力学半径随温度、盐浓度和联接基团长度的变化情况,研究联接基团为聚亚甲基链的阳离子季铵盐Gemini表面活性剂胶团在无机盐介质中的长大规律.实验结果表明,增加盐量、降低温度和减小联接基团的长度均使平均流体力学半径变大,Gemini表面活性剂胶团长大时是由球状转变为棒状.从实验测定的平流体力学半径求算了支配球-棒转变的平衡常数及热力学函数值,并用NNLS(non-negatively constrainedleast square)算法对胶团的粒径分布情况进行了分析.此外,对具有短联接基团的Gemini表面活性剂胶团长大所具有的独特性质进行了讨论.     

Solution Behavior of Poly(n-Isopropylacrylamide) in Water: Effect of Additives

The effect of different kinds of additives (electrolytes, nonelectrolytes, hydrotropes, and surfactants) on the cloud point (CP) of low molecular weight and narrow dispersed poly(n-isopropylacrylamide) (PNIPAM) synthesized via reversible addition-fragmentation chain transfer (RAFT) controlled radical polymerization was examined. The CP showed a concentration dependent variation and it is greatly modified in the presence of additives. The size of the random polymer coil at 30°C obtained from dynamic light scattering (DLS) measurements is often influenced by the presence of additives. We have explained the effects of different additives on PNIPAM in terms of their interaction with polymer and resultant changes in the coil structure.     

疏水缔合聚丙烯酰胺在盐水中的自组装行为

使用静态光散射、动态光散射以及原子力显微镜(AFM)研究了疏水缔合聚丙烯酰胺(HAPAM)在盐水溶液中的自组装行为.研究了聚合物分子在不同盐浓度中的表观重均分子量(Mw,a),均方根回转半径(),流体力学半径(),第二维里系数(A2)的变化,并根据/的比值得出聚合物分子的聚集形态.实验结果表明:随着盐浓度的增强,聚合物溶液的分子链由舒展变得卷曲.     

季铵盐Gemini表面活性剂胶团水溶液的流变性质

用毛细管振荡剪切流动法研究联接基团为聚亚甲基链的季铵盐型Gemini表面活性剂C_12-s-C₁₂·2Br(s=2,4,8)的流变性质,并用动态光散射技术测定胶团生长过程中的胶团形状和大小的变化规律,探索联接基团长度对胶团形状、大小以及溶液流变性质的影响.实验结果表明,胶团形状和大小与联接基团长度有关,而溶液的流变性质主要由胶团的大小和形状所决定,球形和棒状(长椭球体)胶团溶液的流变性质以纯粘度为主,而线性胶团溶液则显示粘弹性质.此外,增加电解质浓度和降低温度均使溶液的粘度增大.     

丙三醇对水溶液中血红蛋白构象的影响——荧光猝灭和动态光散射研究

利用荧光猝灭法和动态光散射法测定丙三醇-水混合溶剂中血红蛋白(Hb)与联苯胺的结合距离和Hb的流体动力学半径, 并通过分析Hb荧光光谱和吸收光谱的变化, 探讨丙三醇与蛋白质分子在水溶液中相互作用的机理及其对蛋白质构象的影响. 结果表明, 丙三醇-水混合溶剂中Hb通过优先水化作用形成更紧密的构象, 溶剂体系的氢键形成能力下降对稳定蛋白质的构象有重要的影响, 丙三醇浓度较高的混合溶剂中氢键网络发生崩塌, 导致蛋白质构象产生进一步的折叠. 实验显示, 尽管Hb在丙三醇-水混合溶剂中保持较完整的血红素疏水空穴结构, 但是血红素疏水空穴以外肽段的构象发生显著变化, 并对血红蛋白的聚集状态造成一定的影响.     

Rheology of Aqueous Solutions Containing SLES,CAPB, and Microemulsion: Influence of Cosurfactant and Salt

Aqueous solutions containing sodium lauryl ether sulphate (SLES) and cocamidopropyl Betaine (CAPB) with a constant total surfactant concentration (10 wt%) but different volume mixing ratios were prepared. A remarkable increase in the solutions’ viscosity at a volume mixing ratio of 34 v/v% SLES to 66 v/v% CAPB was observed. By increasing the volume ratio of SLES (r-value) in the binary mixture, the viscosity of 10 wt% SLES, which is close to that of water, increases to a maximum, but then drops down drastically at high r values (>45 v/v%). The maximum viscosity (V_max) is 2.8 Pas, whereas the minimum is 2 mPas. The rheological behavior at V_max has the remarkable feature of a simple Maxwell fluid over a large frequency range with one relaxation time. By adding a microemulsion (Plantasil Micro), the value of V_max decreases extremely, whereas adding cosurfactants like isodecyltrietheleneoxide (IT₃) or salts, like calcium chloride, leads to a pronounced increase in the value of V_max. At 0.76 wt% CaCl₂, V_max is 140 Pas and 150 Pas in the presence of 1 wt% IT₃. By increasing the SLES volume mixing ratio in the solution the maximum viscosity is shifted to higher CaCl₂ amounts. The increasing viscosity can be explained by a transformation of the micelle shape from spherical to rod-like. Whereas adding cosurfactants or salts leads to an increased entanglement between the rod-like micelles. Consequently, higher microemulsion amounts can be added before reaching the minimum viscosity.     

Dynamic Interfacial Behavior of Poly(oxyethylene) Lauryl Ether Based Surfactant Mixtures

The adsorption behavior of binary mixtures comprising nonionic surfactants at the air–water interface has been studied by bubble pressure tensiometry at concentrations above and below their critical micelle concentrations. Surfactants with the same hydrocarbon chains but different degree of ethoxylations were chosen as the components to understand their mixing behavior at equilibrium and dynamic conditions. At short times, the adsorption is found to be diffusion limited for individual components as well as for the mixtures, as predicted by the Ward and Tordai model. The effective diffusion coefficient of the monomers in the mixed state displays a dynamic synergism, consistent with the molecular thermodynamic model for dynamic surface tension. However, the equilibrium surface tension and micellar diffusion coefficient of the mixtures exhibit ideal behavior.     

Role of the Surfactant Structure in the Behavior of Hydrophobic Ionic Liquids within Aqueous Micellar Solutions

The behavior of an ionic liquid (IL) within aqueous micellar solutions is governed by its unique property to act as both an electrolyte and a cosolvent. The influence of the surfactant structure on the properties of aqueous micellar solutions of zwitterionic SB‐12, nonionic Brij‐35 and TX‐100, and anionic sodium dodecyl sulfate (SDS) in the presence of the “hydrophobic” IL 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim][PF₆]) is assessed along with the possibility of forming oil‐in‐water microemulsions in which the IL acts as the “oil” phase. The solubility of [bmim][PF₆] within aqueous micellar solutions increases with increasing surfactant concentration. In contrast to anionic SDS, the zwitterionic and nonionic surfactant solutions solubilize more [bmim][PF₆] at higher concentrations and the average aggregate size remains almost unchanged. The formation of IL‐in‐water microemulsions when the concentration of [bmim][PF₆] is above its aqueous solubility is suggested for nonionic Brij‐35 and TX‐100 aqueous surfactant solutions.     

十六烷基三甲基氯化铵在β-环糊精水溶液中的胶束化行为

通过测定十六烷基三甲基氯化铵（CTAC）+H_2O和CTAC+β-环糊精（β-CD） +H_2O体系在298.15K时的电导和密度，计算了一系列重要的热力学参数，如临界胶 束浓度、胶束离解主工、CTAC分子碳链从β-环糊精水溶液到胶束的转移自由能、 CTAC的标准偏摩尔体积以及CTAC和β-CD形成的包络物的计量比和包络常数等，结 果表明，β-CD对CTAC的胶束化有较显蓍的影响，由于CTAC的疏水碳链被β-CD空腔 包络，CTAC的热力学活度降低，削弱了其胶束的生成，但是，β-CD及其包络物基 本上不参与CTAC胶束的生成，而且一旦胶束形成，包络物对CTAC的胶束性质也没有 明显的影响，在简单模型的基础上不参与CTAC胶束的生成，而且一旦胶束形成，包 络对CTAC的胶束性质也没有明显的影响，在简单模型的基础上，计算了CTAC分子碳 链进入β-CD疏水空腔的CH_2基团的数目，从另一方面证明β-CD与CTAC分子形成了 包络物，当β-CD的浓度较高时，包络物的计量比为2∶1。     

Cloud point analysis: Influence of additives on polysorbate

The solution properties of nonionic surfactants are significantly diverse from those of ionic surfactants. Additives to nonionic surfactant solution do change the cloud point (CP). In this article, we report the CP data of polysorbate 20 (tween-20) and polysorbate 80 (tween-80), nonionic surfactants, in the presence of various additives and also focus on their characteristics. It is observed that the micellization tendency of the polysorbates changes in the presence of different additives. The addition of different variants of salts decreases the CP of polysorbates solutions. Furthermore, the higher the valency of the cation, the lesser is the depression in the CP of the polysorbates. Overall monovalent, di-valent and a mixture of di-valent salts have large affinity to alter the values of CP of polysorbates, because of their effect on the water structure and their hydrophilicity. An effort has been made to understand the influence of various combinations of salts on polysorbates.     

Interfacial Properties of Aqueous Nonionic Fluorocarbon Surfactant Solutions

The equilibrium, dynamic surface tensions, and surface dilatational elasticity of aqueous solutions of nonionic fluorocarbon surfactant are reported. The critical micellar concentration, CMC (0.023 mM) and equilibrium surface tension (24.6 m N . m^?1) at CMC were measured by Wilhelmy plate method for aqueous solution of C₈F₁₇SO₂N(C₃H₇)(C₂H₄O)_nH (n=20), abbreviated as EF122A. The surface tension decay is slower for C₈F₁₇SO₂N(C₃H₇)(C₂H₄O)_nH (n=10) system, abbreviated as EF122B compared to the EF122A system over short time region, which indicates the slow transport of the surfactant molecules to the surface. The relaxation time for surface tension decay is estimated by fitting a series of exponentials to the dynamic surface tension data and it decreases with temperature for EF122A. Slow exchange of monomers between bulk and interface is reflected in the high elasticity value of the air‐liquid interface for EF122B compared with EF122A within measured frequency window (0.125–1.25 Hz).     

Micellization and Interaction Properties of Aqueous Solutions of Mixed Cationic and Nonionic Surfactants

The micellization process of binary surfactant mixtures containing cationic surfactants viz. dodecyl pyridinium halide (C₁₂PyX; X=Cl, Br, I), tetradecyl pyridium bromide (C₁₄PyBr), and hexadecyl pyridium halide (C₁₆PyX; X=Cl, Br) and a nonionic surfactants viz. dodecyl nonapolyethylene glycol ether (C₁₂E₉), dodecyl decapolyethylene glycol ether (C₁₂E₁₀), dodecyl dodecapolyethylene glycol ether (C₁₂E₁₂), and dodecyl pentadecapolyethylene glycol ether (C₁₂E₁₅) in water at different mole fractions (0–1) were studied by surface tension method. The composition of mixed micelles and the interaction parameter, β evaluated from the CMC data obtained by surface tension for different systems using Rubingh's theory were discussed. Activity coefficient (f₁ and f₂) of cationic surfactant (C_nPyBr)/C₁₂E_m (n=12, 14, 16 and m=10, 12, 15) mixed surfactant systems were evaluated, which shows extent of ideality of individual surfactant in mixed system. The stability factors for mixed micelles were also discussed by Maeda's approach, which was justified on the basis of steric factor due to difference in head group of nonionic surfactant.     

Interaction Mechanisms Between Anionic Surfactant Micelles and Different Metal Ions in Aqueous Solutions

In its using or eliminating processes, surfactant solutions usually exhibit different behaviors because of the different species or concentrations of the encountered metal ions. Interactions between anionic surfactant (SDS) micellar solutions and several familiar metal salt solutions (Al₂(SO₄)₃, FeCl₃, CaCl₂ and MgCl₂) were investigated. Precipitates were formed in all systems except SDS‐MgCl₂ visually. Stoichiometric analysis reveals that, in SDS‐Al₂(SO₄)₃ system, the precipitation phenomenon is mainly owing to the effect of adsorption‐charge neutralization between Al³⁺ ions and SDS micelles; in SDS‐FeCl₃ system, bridge connection effect of Fe(OH)²⁺ ions among SDS micelles becomes the dominant mechanism; while in SDS‐CaCl₂ system, all SDS micelles are decomposed and solubility product of Ca(DS)₂ crystal results in the precipitation. SEM photographs of the precipitates can serve as additional vivid proofs of the above conclusion.