牛血清白蛋白对Pluronic聚合物胶团形成的影响研究

用吡啶作为荧光探针研究了嵌段共聚物PluronicF108胶团形成以及牛血清白蛋白(BSA)对嵌段共聚物胶团形成的影响。研究表明,BSA阻碍嵌段共聚物的胶团形成,BSA与嵌段共聚物疏水链段的疏水相互作用是其阻碍嵌段共聚物胶团形成的主要原因。     

C12-s-C12·2Br与低碳醇混合水溶液胶团化行为的温度效应和焓/熵补偿

季铵盐Gemini表面活性剂C12-s-C12·2Br(s=2,3,4,6)与丙醇、丁醇、戊醇、己醇混合水溶液的In(cmc)随温度升高而逐渐增大.计算所得热力学数据表明,C12-s-C12·2Br与醇混合胶团化过程服从熵驱动机理,也出现了焓/熵补偿现象.随着温度上升,熵驱动力增大,在指定温度时,醇分子烷烃链上碳原子数n增大使△Gm0值减小,胶团结构更加稳定;而增加s使值增大,胶团稳定性下降.     

Binding studies of sodium dodecyl benzene sulphonate with poly(N-vinyl-2-pyrrolidone)

The binding of sodium dodecyl benzene sulphonate (SDBS) with poly(N-vinyl-2-pyrrolidone) (PVP) has been investigated at 303.15 and 313.15 K using equilibrium dialysis, surface tension, viscosity, ultrasound velocity and ultrasound absorption techniques. From each of these studies four distinct regions of SDBS-PVP interactions were observed. Interaction of SDBS with PVP was found to involve the binding of surfactant dimers with the polymer molecule followed by usual micellization. The binding data has been analyzed in terms of various models of polymer-surfactant interaction.     

Ga^3＋的新萃取体系的界面特性和胶团化作用研究

研究了Ｇａ~（３＋）协萃体系（Ｇａ~（３＋）－Ｄ_２ＥＨＰＡ－Ｈ_２ＭＰＡ－正十二烷－Ｈ_２ＳＯ_４）的界面吸附和胶团形成热力学，发现该萃取体系中［Ｈ_２ＭＰＡ］影响Ｄ_２ＥＨＰＡ和Ｈ_２ＭＰＡ的界面吸附性质。在中、高［Ｈ_２ＭＰＡ］范围内Ｄ_２ＥＨＰＡ与Ｈ_２ＭＰＡ的界面吸附行为相反，Ｄ_２ＥＨＰＡ的存在也影响Ｈ_２ＭＰＡ的界面吸附行为。研究了界面张力与各因素关系的数学模型，并获得某些胶团形成和界面吸附特性的物化参数。     

Micellization and morphological characterization of Ag-micelles prepared by poly(vinyl acetate)–silver nitrate in solvent/nonsolvent system

The inducing method for preparing Ag-micelle solution with the use of mixed solvent/nonsolvent, and the morphological characterization of the generated metal–micelles were investigated and reported in this paper. In this method, an Ag containing metal chelate polymer (MCP) raw solution was preprepared by dissolving poly(vinyl acetate) (PVAc)–silver nitrate (AgNO₃) MCP in conc. formic acid, and a mixed solvent of HCOOH/H₂O with specific water composition was then added to induce the micellization of the MCP chain. The critical water concentration (CWC) that was needed for inducing the formation of the Ag-micelles, and the water concentration at which the flocculation of the Ag-micelles occurred in micellar solution, were studied by measuring the transmittance of the dilute MCP solution; the results showed that a long-lasting MCP solution with stable micelles might be prepared by using a H₂O/HCOOH solvent of specific weight ratio 1:1.2. The effect of the AgNO₃ concentration on the morphology of the Ag-micelles was also investigated by transmission electron microscopy (TEM). At AgNO₃ concentration below 0.5 wt%, the Ag-micelles displayed a variety of core-shell structure; but as the AgNO₃ concentration was increased to 1.0–2.0 wt%, micelles that had Ag-solid embedded in the micellar core were observed.     

Kinetics of the surface tension of micellar solutions: Comparison of different experimental techniques

The kinetics of the surface tension of micellar solutions of nonionic surfactant Triton X-100 is measured experimentally by means of three different techniques: oscillating jet, maximum bubble pressure and inclined plate. They allow to study the micellization kinetics at various time scales (from a few milliseconds to a few seconds) in fairly large concentration region up to 50 times CMC. The experimental data are satisfactorily explained by a theoretical model accounting for the kinetics of micellization, diffusion of surfactant species and expansion of the bubble interface. By this model are computed the characteristic times of diffusion and micellization, which are of comparable magnitude (about 5 to 200 ms), and the Gibbs' elasticity. The micellization time constant corresponds to the slow relaxation process known to coincide with the disintegration of micelles. Comparing our data with other data from literature one can conclude that more realistic information for the micellization kinetics is obtained by the maximum bubble pressure and the oscillating jet method. The inclined plate seems too slow to measure the relaxation processes in micellar solutions of this surfactant.     

Micellization and adsorption of a zwitterionic surfactant: N-dodecyl betaine-effect of salt

Time-resolved fluorescence quenching, self-diffusion measurements and calorimetric investigations have been used in order to investigate the effect of salt on aggregation in aqueous solutions and the adsorption onto silica gel of the zwitterionic surfactant N-dodecyl betaine (NDB).

The micelle aggregation number of NDB stays constant when the NDB or salt concentration increases but decreases with an increase of temperature. Evidence is presented for the binding of cations and anions to micellar aggregates. The degree of binding has been obtained for Na⁺, Ca²⁺ and Cl⁻ ions; it is always larger for the anion.

Enthalpies of micellization were obtained directly from calorimetric curves of NDB in dilution experiments. The observed decrease of the endothermic enthalpies of micellization with increasing temperature or salinity is attributed to a structural change in the water molecules around the alkyl chain of the free monomers.

The adsorption isotherms of NDB onto silica gel depend very little on temperature, and a plateau is reached near the CMC. At saturation, the adsorbed amount of NDB depends on the salt and follows the sequence NDB < (NDB + NaCl) < (NDB + CaCl₂).

The exothermic differential molar enthalpies of adsorption demonstrate the same behaviour as the enthalpies of micellization with varying temperature or salinity. Adsorption onto silica gel depends on the NDB concentration, the salt concentration and temperature.     

Conductometry and Thermodynamics Study of Metal Dodecyl Sulfates in Aqueous Solution

The aggregation behavior of metal dodecyl sulfates (MDS), [Na¹⁺, Mg²⁺, Mn²⁺, Co²⁺, and Ni²⁺] in water has been studied by electrical conductivity (at 293.15–333.15 K) and surface tension methods (at 303.15 K). Critical micelle concentrations (CMCs), degree of counterion dissociation (β) evaluated from conductivity data. Using law of mass action model, the thermodynamic parameters viz. Gibbs energy (ΔG_m ⁰), enthalpy (ΔH_m ⁰), and entropy (ΔS_m ⁰) were evaluated. The enthalpy of micellization decreases strongly with increasing temperature. ΔG is always negative (thermodynamically favored process) and slightly temperature and counterion dependent. Gibbs energy and entropy exploit micellization as thermodynamic favorable process. The electrostatic repulsions between ionic head groups, which prevent the aggregation, are progressively screened as the ionic character decreases with the size of the counterion. The plots of differential conductivity, (dk/dc) _T,P , versus the total surfactant concentration enables us to determine the CMC values more precisely than the conventional method. Surfactants with strong condense counterion are adapted to rodlike micelle better than to a spherical micelle. The data are explained in terms of molecular characteristics of surfactants viz. degree of dissociation, polar head group size and counterion.     

MICELLIZATION STUDIES OF DODECYL BENZENESULFONIC ACID AND ITS INTERACTION WITH POLYVINYLPYRROLIDONE

Dodecyl benzenesulfonic acid (DBSA) surfactant was used in the present study to find the effect of concentration on its electrical conductance in solution from 293-323K above and below the critical micelle concentration (CMC). The micellization parameters i.e. degree of counter ion binding (β), aggregation number (n) and number of counter ion micelle(m) were measured. The interaction of DBSA with polyvinylpyrrolidone (PVP) was also studied at 293K throughconductance and surface tension measure ments. A number of important parameters i.e. critical aggregation concentration (CAC), Gibb‘s free energy (△G) and binding ratio (R) were determined and the effect of NaCl on the CAC and polymer saturation point (PSP) was also investigated.     

核磁共振谱研究PAA-F108-PAA 嵌段共聚物的胶束化行为

采用原子转移自由基聚合伴随水解的方法合成了聚丙烯酸-聚醚嵌段共聚物(PAA-F108-PAA), 并通过氢核磁共振波谱和二维核Overhauser效应谱(2D NOE)研究了温度、 羧酸基团中和度(α)及盐浓度对PAA-F108-PAA嵌段共聚物在水溶液中胶束化行为的影响. 结果表明, PAA-F108-PAA分子的临界胶束化温度受α影响较小, 受盐的种类和浓度影响较大. 当α=0.14(0.01 mol/L KCl)时, 在6 ℃条件下, PAA-F108-PAA分子处于塌缩状态, 而在60 ℃条件下, 聚氧化丙烯(PPO)链段发生疏水聚集形成胶束的核, PAA链段与PEO链段相互作用形成胶束的壳; 当α=0.80(0.01 mol/L KCl)时, 在6 ℃条件下, PAA-F108-PAA分子处于相对伸展状态, 而在60 ℃条件下, PPO链段仍发生疏水聚集形成胶束的核, PEO与PAA彼此分离形成胶束的壳. 增加KCl的浓度至1 mol/L, PAA-F108-PAA分子的临界胶束化温度显著降低, KCl对PPO和PEO链段都表现出脱水作用. 但KI的浓度增加至1 mol/L时, PAA-F108-PAA分子的临界胶束化温度仅略微增加, KI对PPO链段表现出脱水作用, 而对PEO链段表现出增溶作用.