磷脂单分子膜普适状态方程研究

从现有的磷脂单分子膜状态方程入手, 以磷脂临界相变面积(A_c)和相变温度(T_c)为参比, 引入对比面积(A_r), 对比温度(T_r), 并通过分析磷脂分子间作用力和底液分子与磷脂分子间作用力的影响, 提出了第三参数——相对铺展因子的概念, 导出了磷脂单分子膜普适状态方程. 运用1,2-二豆蔻酰基-sn-丙三基-3-磷脂酸, 1,2-二豆蔻酰基-sn-丙三基-3-磷脂酰胆碱, 1,2-二棕榈酰基-sn-丙三基-3-磷脂酰胆碱等磷脂单分子膜的实验数据进行一致性校验的结果表明, 该模型在扩展膜(LE)直至凝聚膜(LC)的整个区域均能较好地描述磷脂单分子膜的π-A曲线. 所获得的各磷脂的相对铺展因子绝对值直接表明了该物质的成膜特性.     

季铵盐型双子表面活性剂与十八醇的混合单分子膜

研究了双子表面活性剂12-2-16和12-2-12分别与十八醇(C18H37OH)在空气-水界面上混合单分子膜的π-A等温线. 在相分离表面压以下, 比较了不同表面压下和不同混合比单分子膜的混合表面过剩自由能ΔGMexo, 分析了双子表面活性剂与脂肪醇在空气-水界面上混合膜中的相容性. 结果表明, 12-2-16与C18H37OH在所有混合摩尔比下随着表面压增高, 自由能增大. 12-2-12与C18H37OH混合膜体系的相容性取决于两者的混合比, ΔGMexo随所加入C18H37OH摩尔分数的增加逐渐增大, 从异种分子间净的吸引作用转变到相互排斥作用体系, 转变点为C18H37OH加入量的摩尔分数0.65. 当混合为热力学自发过程时, 增大表面压将有利于混合; 而对相互排斥体系, 增加表面压将使体系内异种分子之间的相互排斥作用更大.     

Gemini表面活性剂/C12En混合体系的界面吸附、扩张粘弹与泡沫稳定性

用表面张力法研究了阳离子gemini表面活性剂乙基-1, 2-双(十二烷基二甲基溴化铵)(简写为12-2-12)和非离子表面活性剂十二烷基聚氧乙烯醚(C₁₂E_n,其中n = 4, 10, 23)混合体系在气液界面上的吸附行为;用扩张流变技术研究了吸附膜的扩张粘弹行为,实验数据用Lucassen-van den Tempel (LVT)模型进行拟合并根据模型得到了极限弹性值.最后研究了混合体系的泡沫行为,用泡沫塌陷到初始高度一半所对应的时间(t_1/2)来表征泡沫的稳定性.结果表明,所有的非离子表面活性剂C₁₂E_n均与12-2-12产生了吸引作用.在12-2-12浓度相同的情况下,混合吸附层中吸附分子的最小分子占据面积的顺序为12-2-12/C₁₂E₂₃ > 12-2-12/C₁₂E₁₀ > 12-2-12/C₁₂E₄,而极限弹性的顺序为ε_{0, fit}(12-2-12/C₁₂E₄) > ε_{0, fit}(12-2-12/C₁₂E₁₀) > ε_{0, fit}(12-2-12/C₁₂E₂₃).与单组分12-2-12形成的吸附膜相比,只有12-2-12/C₁₂E₄形成更加紧密的结构.具有较小亲水头基的非离子表面活性剂C₁₂E₄的加入,可增强12-2-12吸附膜的弹性,进而增强了对应体系泡沫的稳定性.     

胆固醇/两性霉素B混合单层膜相互作用的研究

两性霉素B (AmB)为多烯类抗真菌抗生素, 它的吸收过程与生物膜有密切联系. 选用生物膜中的重要分子胆固醇为代表, 通过Langmuir-Blodgett (LB)膜技术测得胆固醇/两性霉素B单层膜表面压力与平均分子面积(π-A)曲线, 定量分析了固定模压下的平均分子面积(A)、弹性模量(C_S^－1)、过量吉布斯自由能(ΔG_ex)等参量. 实验结果表明, 胆固醇/两性霉素B两组分物质的量比与膜压对单层膜的弹性、稳定性以及热力学特性有影响|通过单层膜相互作用参数α进一步佐证了组分间物质的量比和表面压力对混合单层膜稳定性、混合性以及分子间相互作用具有重要影响.     

C12-m-C12型阳离子Gemini表面活性剂在煤沥青表面的润湿性

利用座滴法和电泳法研究了阳离子Gemini表面活性剂C₁₂-m-C₁₂·2Br^-(m=4、6、8、10)在煤沥青表面的润湿性质及吸附机理。结果表明, 表面张力均随表面活性剂浓度的增大而减小, 超过临界胶束浓度(CMC)后趋于平稳, 接触角θ和铺展系数S的变化趋势与表面张力类似; 在所研究浓度范围内,C₁₂-10-C₁₂型表面活性剂的γ_lg~cosθ曲线符合Zisman理论, 且侵湿功(W_i)与表面张力也呈线性关系; 煤沥青表面的Zeta电位随表面活性剂浓度的增加从负电变为正电,最后趋于平稳, 且零电位对应的浓度比CMC至少低一个数量级; C₁₂-8-C₁₂型Gemini表面活性剂能显著改变煤沥青表面的润湿性. 由Gemini表面活性剂在煤沥青表面润湿结果及Zeta电位可以看出, C₁₂-m-C₁₂型Gemini表面活性剂在煤沥青表面的润湿是静电作用和范德华吸附共同作用的结果; 润湿过程可分为三个阶段。     

气相二氧化硅/季铵Gemini表面活性剂稳定的泡沫体系

以zeta电位法研究了季铵Gemini表面活性剂亚甲基-α, ω-双(十二烷基二甲基溴化铵) (12-s-12, s=2, 6)在水溶液中修饰气相二氧化硅(F-SiO₂)粒子。这些粒子随表面活性剂浓度C增加经历了表面从原先的亲水到疏水再重新亲水的改变,其中疏水粒子可以自发吸附在气泡液膜中,从而很好地稳定泡沫。重新亲水的粒子脱附出液膜,仅留下表面活性剂稳定气泡。强的液膜弹性对应于稳定的泡沫。联接链长度影响了Gemini在F-SiO₂粒子表面的吸附,因而也影响了液膜的弹性和对泡沫的稳定。超短s=2联接链的12-2-12由于反离子解离不完全而带有较少的正电荷,在粒子表面的初始吸附弱于12-6-12,但因此减少了吸附分子头基间的静电排斥,可以形成更致密的吸附层。由于12-2-12本身比12-6-12具有更强的界面吸附能力,F-SiO₂粒子和12-2-12的协同作用可以更好地稳定泡沫体系。     

不同寡聚度磺酸盐表面活性剂与支化羧酸盐混合体系的聚集行为

采用表面张力、Zeta电位和小角中子散射技术,研究了pH 11条件下2-己基癸酸、异硬脂酸对具有单头单链十二烷基磺酸钠（SDoS）和星状四聚磺酸盐表面活性剂EDA-（C₁₂SO₃Na）₄的气液界面性质、胶束化行为和乳化性能的影响.结果表明,在气液界面和胶束中支化羧酸盐分子与磺酸盐表面活性剂间有不同程度的相互吸引作用,而且在降低表面张力效率方面具有协同作用,但胶束中分子间相互吸引作用更强的四聚磺酸盐表面活性剂混合体系在聚集体形成方面却未表现出协同作用.同时,随着羧酸盐的加入,SDoS和EDA-（C₁₂SO₃Na）₄呈现出不同的聚集体转变规律,羧酸盐与SDoS的混合聚集体随着浓度增大逐渐由球形胶束转变为棒状胶束,而羧酸盐与EDA-（C₁₂SO₃Na）₄的棒状胶束随着羧酸盐摩尔分数的增大而增长,随着总浓度的增大而减小.此外,在同等乳化烷烃的效果下,支化羧酸盐分子的加入可以大幅减少寡聚磺酸盐表面活性剂的使用量.     

分子模拟方法考察泡沫生成能力

采用分子模拟的方法研究表面活性剂的泡沫生成能力, 以界面形成能作为考察泡沫体系中液膜界面积的量化依据, 研究了泡沫液膜厚度、表面活性剂分子界面密度以及表面活性剂类型对泡沫液膜界面形成能计算的影响. 通过与实验结果相对应, 建立了界面形成能和泡沫生成能力之间的联系.     

含双疏水链阴离型两性分子单分子膜的聚集行为

单分子膜在水面上的聚集状态与膜分子的亲水基间的静电排斥作用和疏水基间Van der Waals引力的相对大小有关.在293K亚温度下,2C~nSN~a单分子膜聚集行为的电子显微研究表明,n=12时呈非晶性单分子;n=12时在较高的表面压下形成结晶性单分子膜;n=16时可在表面压为0mN.m^-1的情况下形成结晶性单分子膜.FT-IR和透射电镜对单分子膜聚集结构的解析结果相互一致.本文还讨论了压缩速度对单分子膜π-A等温线的影响.     

含双疏水链阴离型两性分子单分子膜的聚集行为

单分子膜在水面上的聚集状态与膜分子的亲水基间的静电排斥作用和疏水基间Van der Waals引力的相对大小有关.在293K亚温度下,2C~nSN~a单分子膜聚集行为的电子显微研究表明,n=12时呈非晶性单分子;n=12时在较高的表面压下形成结晶性单分子膜;n=16时可在表面压为0mN.m^-1的情况下形成结晶性单分子膜.FT-IR和透射电镜对单分子膜聚集结构的解析结果相互一致.本文还讨论了压缩速度对单分子膜π-A等温线的影响.     

Aggregation behavior and adsorption properties of salt-free catanionic surfactant mixtures containing tetradecyltrimethyl ammonium salts

The aggregation behavior of salt-free catanionic surfactants, tetradecyltrimethyl ammonium hydroxide (TTAOH)/fatty acid (FA) including octanoic acid (OA), decylic acid (DA) and lauric acid (LA) in aqueous solutions were studied. The critical micelle concentration(cmc), surface tension at cmc (γ_cmc), surface excess (Г_max), mean molecular surface area (A_min), adsorption efficiency (pc₂₀) and surface tension reduction effectiveness (π_cmc) were obtained from surface tension isotherms. The influence of temperature on the surface tension of salt-free TTAOH/FA (TTAOF) systems was investigated. Data of adsorption dynamics indicated that at fixed adsorption time, the order of adsorption capacity was TTAOH?相似文献   

Synthesis,surface activity,and corrosion inhibition of dentritic quaternary ammonium salt-type tetrameric surfactants

The dentritic quaternary ammonium salt-type tetrameric surfactant (4C₁₂tetraQ) was synthesized, and the molecular structure was confirmed by ¹H NMR and FTIR. The surface activity of 4C₁₂tetraQ was investigated by surface tension, and surface chemical parameters, such as critical micelle concentration (cmc), efficiency (pC₂₀), effectiveness (π_cmc), the surface tension value at cmc (γ_cmc), minimum surface area (A_min), maximum surface excess (Γ_max), and cmc/C₂₀ were obtained from the measurement results. The results show that the 4C₁₂tetraQ surfactant has higher surface activity than the traditional monomeric surfactants (dodecyl trimethyl ammonium bromide, DTAB). The Krafft points were taken as <0°C, indicating that the synthesized tetrameric surfactants had good water solubility. Free energies of micellization and adsorption show that 4C₁₂tetraQ display greater propensity to absorb at the interface than form micelle in the bulk of the aqueous solution, and that the two processes are spontaneous. The measurement results show that 4C₁₂tetraQ has good emulsification power and foam performance. The corrosion efficiency was evaluated with the loss weight method in 1?mol/L HCl solution, and the results show that the 4C₁₂tetraQ surfactant has good corrosion inhibition, and can be considered as a corrosion inhibitor.     

Mixed micellization and surface properties of non-ionic/cationic surfactants

We investigate the surface properties of aqueous binary mixtures of our cationic surfactant O-dodecyl-N,N′-diisopropylisourea hydrochloride (ISO-DIC C₁₂) with commercially available nonionic surfactant polyoxyethylene p-(1,1,3,3-tetramethylbutyl)phenyl ether (TritonX-100) at different temperatures (288 to 303?K). The micellization behavior of the binary systems is studied by determining the surface tension and other important physicochemical parameters, such as the critical micelle concentration (CMC), surface tension at the CMC(γ_cmc), Krafft Temperature (T_K), maximum excess concentration (Γ_max), minimum surface area per molecule (A_min), surface pressure at the CMC (П_cmc), and the adsorption efficiency (pC20) at the air/water interface. The study has additionally covered the calculation of thermodynamic parameters of micellization, including the standard Gibbs free energy, the standard enthalpy, the standard entropy, the free energy, and the Gibbs free energy of adsorption at air/water interface. The CMC values of the binary systems determined by experimental data are used to evaluate the micellar composition in the mixed micelle, the interaction parameter β and the activity coefficients f₁(ISO-DIC C₁₂) and f₂ (polyoxyethylene p-(1,1,3,3-tetramethylbutyl)phenyl ether) using the theoretical treatment proposed by Clint and Rubingh. Our results reveal that the proposed binary systems possess enhanced surface activity compared to those of the individual surfactants.     

Thermodynamic properties of ibuprofen sodium salt in aqueous/urea micellar solutions at 298.15 K

Thermodynamic, surface and micellar properties of anti-inflammatory drug sodium 2-(4-isobutylphenyl) propionate (sodium salt of ibuprofen (NaIBF)) in aqueous/urea solution were studied by surface tension measurements at 298.15 K in the presence of anionic surfactant sodium dodecylsulfate (SDS). Critical micelle concentration (cmc), surface tension at cmc (γcmc), maximum Gibbs surface excess (Γ_max), minimum surface area per surfactant molecule at the air/water interface (A _min) etc. were determined in pure water as well as in aqueous urea solution. The theories of Clint, Rosen and Rubingh have been applied to describe the interactions between these amphiphiles at the interface and in the micellar solution. Various thermodynamic parameters have been calculated and discussed in detail.     

Synthesis and properties of double-chain single-head acetamidinium bicarbonate switchable surfactants

A series of switchable surfactants with double hydrophobic chains and a single hydrophilic head N,N’-dialkylacetamidinium bicarbonate with an alkyl length between diC8 and diC12 were synthesized by using new approaches. The structures of acetamidinium bicarbonate were characterized by ^1?H NMR and ESI-MS spectroscopy. The surface activity in aqueous solution of N,N’-dialkylacetamidinium bicarbonate and N’-alkyl-N,N-dimethylacetamidinium were compared by surface tension methods. Some surface activity parameters were studied, such as cmc, γ_cmc, pC₂₀, cmc/C₂₀, Γ_max, and A_min. The results indicated that double-chain surfactant was superior to single-chain surfactant and showed more excellent surface activity. The switchability was confirmed by monitoring the conductivity of a solution of amidine in ethanol and their effect in emulsion stability was also investigated.     

Synthesis and monolayer film of a series of new twin-tailed gemini cationic surfactants at the air/water interface

A series of new dimeric surfactants, twin-tailed gemini surfactants, 2(12)-s-2(12), were successfully prepared and characterized, and their monolayer films investigated by the measurement of surface pressure-area (π-A) and surface pressure-time (π-t) isotherms at the air/water interface by a Langmuir film balance. Compared to their monomeric counterparts, their collapse pressure (γ_collapse) is smaller, whilst all the molecular area parameters are larger. The limited area (A_limited) and the initial area (A_initial) of these twin-tailed gemini surfactants change with increasing spacer length s, and the surface pressure decreases with increasing time. It was also found that the higher the initial surface pressure, the larger the attenuation.      

Synthesis and Evaluation of Surface Activity of Gemini Borate Surfactants Based on Glucose Moiety

A series of Gemini borate surfactants were synthesized based on glucose molecule. Their chemical structures were confirmed using ¹H-NMR,¹³C nuclear magnetic resonance (NMR), and mass spectroscopy. The surface activities of these Gemini amphiphiles were measured, including surface tension (γ), critical micelle concentration (CMC), effectiveness (II_cmc), efficiency (pC₂₀), maximum surface excess (Γ_max), and minimum surface area (A_min) at different temperatures 25, 35, and 45°C either in pure water or in water–ethanol mixture (10%). Also, thermodynamic data including free energy, entropy, and enthalpy changes (ΔS, TΔS, ΔH) for adsorption at the air–water interface and also for micellization in surfactant solutions were calculated.     

Studies on the Effects of Additional Components on Micellization of CTAB via Surface Tension Measurements

The effects of Tris-HCl buffer solution on the cmc of cetyltrimethylammonium bromide (CTAB) were studied by surface tension measurement. The result shows that the effect of the buffer solution depends on the interaction between CTAB and NaCl and the structure accelerants of water, Tris. A series of parameters, including the critical micelle concentration (cmc), the surface tension at cmc (γ_cmc), the adsorption efficiency (pC₂₀), and the effectiveness of surface tension reduction (∏_cmc) were obtained from the surface tension measurements in the presence of glycine with different concentration in the Tris-HCl buffer solution at 27°C. In addition, maximum surface excess concentration (Γ _max) and minimum surface area per molecule (A_min) at the air-water interface were estimated according to the Gibbs adsorption isotherm. The thermodynamic parameters (Δ C _p,m , Δ H _m,tr , Δ C _p,m,tr ) of micellization for CTAB in the absence and presence of glycine at different temperature were also been obtained.     

Surface activity—thermodynamic properties and light scattering studies for some novel aliphatic polyester surfactants

The preparation of 12 new polyester surfactants based on aliphatic amines and different ethylene oxide content is described. These surfactants were characterized by determining their molecular weights and polydispersity by gel permeation chromatography (GPC) and nitrogen content. Drop volume tensiometry (DVT) was used to measure the surface tension at 25, 35, 45 and 55°C. The surface tension isotherms were used to determine critical micelle concentration (CMC), maximum Gibb's adsorption (Γ_max), minimum area per molecule (A_min), the effectiveness of surface tension reduction (π_cmc) and the efficiency (pC₂₀). The thermodynamic parameters of micellization (ΔG_mic, ΔH_mic, ΔS_mic) and of adsorption (ΔG_ad, ΔH_ad, ΔS_ad) were calculated and the data showed that these surfactants favor micellization to adsorption. The static scattered light intensity measurements provide the calculation of the molecular weight of micelle and the aggregation number (N°), while the dynamic light scattering provide the hydrodynamic radius of micelle (R_H) and the diffusion coefficient at different surfactant concentrations. The hydrodynamic radius of micelle (R_H) at different surfactant concentrations could be used also to determine the CMC giving results that are comparable to those obtained by surface tension measurements. All the data are discussed regarding the chemical structure of the polymeric surfactants. Copyright © 2004 John Wiley & Sons, Ltd.