1H NMR探究空间效应对表面活性剂复配体系中协同作用的影响

通过核磁共振氢谱（¹H NMR）实验测量了温度为298.0 K时3种表面活性剂——十六烷基三甲基溴化铵（CTAB）、辛基苯基聚氧乙烯醚（TX-100）和十二烷基硫酸钠（SDS）组成的复配体系CTAB/TX-100、SDS/TX-100和CTAB/TX-100/SDS中各组分的化学位移,得到了各混合体系中CTAB、TX-100和SDS的临界胶束浓度（CMC）.对不同体系中各组分CMC随摩尔分数的变化曲线进行比较,发现了空间效应对表面活性剂复配体系中协同作用的影响在一定的情况下并不逊于静电相互作用：表面活性剂分子的截面积越大,对体系中其他组分的协同作用越强;当组分间存在弱的静电相互作用时,空间效应对协同作用起到更主要的影响.     

利用1H NMR探究混合离子型/非离子型表面活性剂临界胶束浓度降低的实质

利用¹H NMR技术研究了离子/非离子表面活性剂形成的二元混合体系,结果显示表面活性剂的混合导致各组分的临界胶束浓度（CMC）均比各自纯溶液有所降低,用吸附平衡理论清楚地解释了这个现象.通过定量分析,发现不同的表面活性剂混合使得其组分CMC降低的程度各异,可以理解为它们吸附于界面单分子吸附层上的分子之间相互作用的不同（相吸或相斥）引起的.由此揭示了"协同效应"的实质,可以为选择适当的表面活性剂类型和混合比例以达到预期的性能提供有力的参考.     

TX-100和CTAB交换动力学的核磁共振研究

运用核磁共振(NMR)方法分别测定了表面活性剂辛基苯聚氧乙烯醚(TX-100)和十六烷基三甲溴化铵(CTAB)在不同温度下的临界胶束浓度.阐述了应用1D NMR线型分析方法对表面活性剂快交换体系平均停留时间的定量测量.实验测量了TX-100和CTAB胶束溶液中表面活性剂分子在不同温度下的平均停留时间.结果显示,平均停留时间随温度的增加逐渐减小,说明TX-100和CTAB分子进出胶束的速率随温度的增加逐渐加快.利用阿伦尼乌斯公式拟合,获得了TX-100和CTAB的表观交换活化能,TX-100的表观交换活化能为17.6 k J/mol,CTAB的表观交换活化能为75.3 k J/mol.对TX-100和CTAB平均停留时间和表观交换活化能进行分析,得出平均停留时间和表观交换活化能与分子结构的关系:表观交换活化能反映的是疏水相互作用和静电斥力的大小;而平均停留时间不仅受活化能的影响,还与分子结构有关.     

单链和gemini表面活性剂的NMR研究

应用核磁共振技术,对几种典型的表面活性剂在水溶液中的聚集行为、结构特征、动力学特性和相互作用等进行了研究. 
利用1D ¹H NMR方法测得4-癸基萘磺酸钠（SDNS）在313 K温度时的临界胶束浓度（CMC）在0.82~0.92 mmol/L之间,与报道的298 K时的CMC范围相同. 弛豫时间和2D NOESY实验结果表明,与298 K时的SDNS胶束相比,313 K温度时,SDNS胶束中烷烃链排列得更紧密,其中与萘环相连的第一和第二个亚甲基参与了胶束紧密层的形成,更紧密地堆积在萘环之间. SDNS质子T₂值随温度的变化表明,在单体和胶束两种状态下,质子运动对温度的敏感性明显不同. 由自扩散系数分析得到,SDNS胶束的水合半径约为其单体水合半径的5.3倍. 而在十二烷基磺酸钠（SDSN）胶束中,由于静电排斥力的作用,在同样温度下SDSN的胶束紧密层排列比SDNS更疏松. 
NMR实验表明,在SDNS/Triton X-100 (TX-100)和SDNS/SDSN体系中形成了混合胶束. 在SDNS/TX-100混合胶束中,TX-100的苯环靠近SDNS的烷烃链,而它的聚烷氧链除与苯环相连的第一个乙氧基基团以外都被限制在SDNS的萘环附近. 在SDNS/SDSN混合胶束中,SDSN的磺酸基比SDNS分子更靠近胶束内部. 而SDNS的萘环将SDSN的磺酸基分隔开,在降低带负电荷的磺酸基极性头之间的静电排斥力中起到了积极的作用,有助于混合胶束的形成.
从自扩散系数、横向弛豫和质子距离等NMR测定参数推测,在浓度为0.26 mmol/L（318 K）的N,N′-双(十六烷基二甲基)-α,ω-丙烷溴化铵(16-3-16)溶液中形成了近似球形的胶束,胶束表面的带正电荷的铵基极性头呈锯齿状排列以减弱分子间静电排斥力的影响. 弛豫时间测定表明,与N,N′-双(十六烷基二甲基)-α,ω-丁烷溴化铵(16-4-16)相比,16-3-16在胶束表面的spacer链段更僵硬, 在胶束核区的烷烃侧链排列的更紧密. NMR共振峰的线形分析表明,16-3-16和16-4-16侧链末端的甲基在胶束中位于两个不同的位置.      

表面活性剂在水溶液中聚集状态的1H NMR研究

表面活性剂在水溶液中的自扩散系数,¹H化学位移和自旋晶格弛豫的NMR测量表明,上述参数随表面活性剂浓度而变化,并在某一浓度开始有转折点.这一转折点恰好对应着各自的临界胶团浓度.表面活性剂分子的不同基团的质子化学位移随其浓度变化幅度的不同提供胶团形成的分子水平描述.     

光解丙酮/乙二醇体系的CIDEP实验研究

紫外激光照射下,用时间分辨电子自旋共振(TRESR)波谱仪研究了光解ACETONE/EG体系的化学诱导动态电子极化(CIDEP),得到了丙酮羰自由基(CH3)2C.OH和乙二醇羰自由基CH2OH C.HOH的发射/吸收(E/A)型极化信号,这是一个RPM极化过程.在胶束环境中,不同表面活性剂以及不同的浓度对体系极化的影响是不同的.阳离子表面活性剂CTAB对体系中生成的自由基的极化机理没有产生显著影响,而加入体系中TX-100的浓度对体系的极化机理却产生了很大的影响.在ACETONE/EG体系中,随着TX-100浓度的增加,TM机理对极化强度的贡献明显增大.     

表面活性剂全氟庚酸和全氟辛酸的19F NMR研究

测定了全氟庚酸(PFHA)和全氟辛酸(PFOA)在三氟三氯乙烷或正戊醇溶液中的不同浓度的¹⁹F NMR 化学位移并归属了谱图. 研究了活性剂浓度对化学位移影响的机理和对不同核的不同影响. 由化学位移δ值对浓度倒数作图,可求得活性剂的临界胶束浓度（cmc）：全氟庚酸：0.0195 mol/L (戊醇溶剂)和0.0406 mol/L（三氟三氯乙烷溶剂）;全氟辛酸：0.0547 mol/L（戊醇溶剂）. 用计算模拟法使δ对浓度倒数作图同实验数据作图相比较,可推测得全氟辛酸戊醇溶液的单体分子与胶束大分子的平衡常数为K=21（mol/L）^-(n-1)和胶束聚集数n=3.9.     

表面活性剂及水溶性功能高分子的NMR研究

核磁共振（NMR）技术是研究表面活性剂在溶液中聚集状态的一种非常有用的工具,本文运用多种NMR技术研究了几种不同类型表面活性剂及水溶性功能高分子在水溶液中的聚集行为： 1. 季铵盐型双子表面活性剂16-4-16的聚集行为季铵盐型双子表面活性剂N,N′-双(十六烷基二甲基)-α,ω-丁烷溴化铵(16-4-16)分子中联接基团及靠近离子头的质子位于胶束的壳层, 运动受到一定限制. 而距离离子头较远的烷烃链位于胶束的内部,运动相对自由. 与对应的单链表面活性剂十六烷基三甲基溴化铵(CTAB)相比,16-4-16形成的胶束堆积更为紧密. 通过NOESY谱中交叉峰强度的定量计算,认为16-4-16在胶束中分子以上下交错排列的方式形成球形聚集体.  2. 脱氧胆酸钠与十六烷基三甲基溴化铵的相互作用在脱氧胆酸钠(NaDC)溶液中,NaDC质子H3与其他质子不同,其横向弛豫时间(T₂)表现为双指数衰减,表明此质子可能存在两种不同的状态. 实验证明,其它胆酸盐的H3的横向弛豫也呈现双指数衰减. 因此推测在胆酸盐的稀溶液中,3-OH质子和羰基氧之间有可能存在氢键作用,形成了头尾相连的分子对结构.  在NaDC和CTAB的混合溶液中,两者形成1∶1的混合胶束. 用NOESY和ROESY研究混合胶束的结构,显示CTAB的离子头位于NaDC的羧酸基团附近. 这可能是正负离子之间的静电性相互作用的结果.  3. 丙烯酰胺/丙烯酸模板共聚物的微结构研究了不同pH值条件下,丙烯酰胺和丙烯酸共聚物分子在水溶液中的聚集形态. 在酸性溶液中,分子内的氢键致使聚集体形成较为紧密的堆积,侧链的苯氧基团运动受阻;随着溶液pH值的增大,丙烯酸电离产生的阴离子使得分子间的静电斥力增大,分子链变得伸展,分子间的氢键作用导致了聚集体体积变大. 当溶液呈强碱性,丙烯酸完全电离,氢键作用力被破坏,分子呈现自由伸展的状态,侧链的苯氧基团运动相对自由.     

球状胶束中表面活性剂脱附的离子调控机制

建立耦合伞状采样的粗粒度分子动力学方法,研究球状胶束中表面活性剂分子的脱附过程,揭示表面活性剂聚集数、盐种类及浓度对表面活性剂脱附过程的影响机制。发现球状胶束半径及偏心率均随聚集数增加而增大,盐浓度的影响主要取决于抗衡离子的半径和吸附特性,半径更大、吸附更强的水杨酸根离子对胶束结构的影响更为显著;基于伞状采样方法获得了表面活性剂脱附自由能、脱附时间等关键参数,发现球状胶束中表面活性剂脱附自由能和脱附时间均随聚集数和盐浓度呈非单调变化,揭示其主要机制为离子吸附引起的静电屏蔽作用;发现自由能在表面活性剂脱附过程中起主导作用,结合胶束热力学理论发展了临界胶束浓度预测方法,获得了临界胶束浓度下胶束尺寸的分布范围。     

乙二醇均相及其TX-100胶束溶液中光敏分子菲醌的激光光解研究

用时间分辨电子自旋共振（TR-ESR）和瞬态吸收光谱技术,研究了菲醌在乙二醇均相及其TX-100含水胶束溶液中的光化学反应机理。化学诱导动态电子极化（CIDEP）谱和瞬态吸收光谱都表明,在乙二醇均相溶液中,菲醌光激发三重态3PAQ* 夺取氢原子形成中性自由基PAQH.,三重态机理是CIDEP形成的主要机理。在TX-100含水胶束溶液中,光解主要得到菲醌负离子基PAQ-．,PAQ-．由PAQH.解离形成,解离过程中伴随着极化转移。     

Synthesis and surface activity properties of alkylphenol polyoxyethylene nonionic trimeric surfactants

A series of trimeric n-alkylphenol polyoxyethylene surfactants (TAP) were successfully synthesized and the molecular structure were confirmed by NMR, FTIR spectrum and elemental analysis. Using the same synthesis route, the trimeric nonylphenol polyoxyethylene surfactant (TNP) was synthesized using industrial product nonylphenol and paraformaldehyde, and its molecular structure was characterized by ¹HNMR, FTIR spectrum and elemental analysis. The optimal reaction conditions were established. The surface activity properties of TAP and TNP (such as the critical micelle concentration (cmc), the values of surface tension at the cmc (γ_cmc), the maximum surface excess concentration (Γ_cmc), and the minimum surface area per surfactant molecule (A_cmc)), were determined by means of Wilhelmy plate method and steady-state fluorescence probe method, respectively. The experimental results show that the lengths of the hydrophilic group oxyethylene (EO) chains and hydrophobic group methylene chains have an influence on the cmc, γ_cmc, Γ_cmc, and A_cmc of series of surfactants. Furthermore, TAP are arranged to staggered three-dimensional array mode at the air-water interface, which has exhibited better surface properties, such as low cmc values, strong adsorption affinities and wet abilities.     

Solution properties of phenothiazine drug promazine hydrochloride with cationic hydrotropes in aqueous/electrolyte solution at different temperature

The current work deals with the mixed micellization phenomena of surface active promazine hydrochloride (PMZ) drug with cationic hydrotropes (para‐toluidine hydrochloride and ortho‐toluidine hydrochloride) in absence and occurrence of 50 mmol kg^?1 NaCl at five different temperature (293.15–313.15 K). PMZ is an amphiphilic phenothiazine drug and employed for the cure of mania and schizophrenia. Conductometry measurement was employed to gain a detailed picture of the interactions between drug and hydrotrope molecules. The experimental data were analyzed according to different mixing models within the outline of the pseudophase separation model. The evaluated values of critical micelle concentration (cmc) were found to be inferior than cmc^id values signifying attractive interactions involving the both components in the solutions. NaCl further reduces the cmc of pure amphiphiles and their mixed systems as a result of screening of the electrostatic repulsion between the polar head groups. The micellar mole fractions (X₁) of hydrotropes evaluated by various proposed models were constantly more than ideal values ( ) signifying high involvements of hydrotrope in mixed micelles. Activity coefficients ( and ) were always below one in all cases signifying synergism in mixed micelles. Thermodynamic parameters favor the process of micellization which is found to be entropy driven. The negative values of free energies of mixing demonstrated the stability of the mixed systems of drug and hydrotrope. Copyright © 2016 John Wiley & Sons, Ltd.     

Mixed micellization and interfacial properties of alkanediyl-α, ω-bis(dimethylcetylammonium bromide) in the presence of alcohols

Mixed micellization and interfacial properties of cationic gemini surfactants alkanediyl-α, ω-bis(dimethylcetylammonium bromide) (16-s-16, s = 4,5,6) have been studied in the presence and absence of various alcohols (1,2-butandiol, 2-methyl-1-butanol, 2-ethyl-1-butanol, 2-butene-1,4-diol). Parameters studied include cmc (critical micelle concentration), C₂₀ (concentration required to reduce the surface tension of the solvent by 20 mN/m), Γ_max (maximum surface excess concentration at air/solution interface), and A_min (minimum area per surfactant molecule). These parameters indicate mixed micellization between the surfactants and alcohols. The theories of Rosen and Rubingh have been used to investigate the interactions between the constituents at the interface and in the micellar solution. The micelle aggregation numbers (N_agg) of mixed systems have been obtained using the steady state fluorescence quenching technique. The micropolarity of the systems was also evaluated from the ratio of intensity of peaks (I₁/I₃) of the pyrene fluorescence emission spectrum.     

Surface,micellar, and thermodynamic properties of antidepressant drug nortriptyline hydrochloride with TX‐114 in aqueous/urea solutions

This paper deals with a comprehensive study of the mixed micellization and adsorption behavior of mixed systems enclosing an amphiphilic antidepressant drug nortriptyline hydrochloride (NOT) and Triton X‐114 (TX‐114) (nonionic surfactant) in aqueous/urea (500 mmol·kg^?1 and 1000 mmol·kg^?1) solutions by tensiometric method. The NOT is used for the cure of depression. For comparison purpose cmc value of pure drug NOT was also evaluated by conductimetric technique. Different theoretical models like Clint, Rubingh, and Rosen were used to get information about the nature of interaction between the components in bulk and at the interface. Because of the occurrence of urea increase in the surface charge of the micelles was obtained resulting a delay of the micelles formation. The cmc values of the mixed systems of NOT and TX‐114 were found to be in between the cmc values of pure components, which signify nonideal mixed system having attractive interactions in the absence and presence of urea. Various parameters such as micellar mole fractions of TX‐114 (X₁^m, X₁^σ) in solution and at interface, interaction parameter (β^m/β^σ) in solution and at interface, and activity coefficient in solution and at interface were evaluated and discussed using Rubingh's and Rosen's models. Surface excess (Γ_max) increases that means minimum area per head group (A_min) decreases as mole fraction (α₁) of TX‐114 increases in the absence/presence of urea. Different thermodynamic parameters have been calculated and discussed. The ?G⁰_m values achieved are all negative both in the absence and occurrence of urea.     

表面活性剂CTAB水溶液中的T2弛豫分散研究

用CPMG脉冲序列测定了表面活性剂十六烷基三甲基溴化铵（CTAB）分子中的氮甲基(N-CH₃)质子的横向弛豫时间（T₂表观）,并发现测得的T₂表观\}与序列中的重聚脉冲间隔时间的一半τ _cp有关,说明存在横向弛豫分散现象. 当在τ_cp≤1 ms时,T₂表观与τ²_cp}呈线性关系;而当τ_cp≥4.6 ms时,T₂表观变得与τ_cp无关. 利用Luz-Meiboom两体化学交换模型计算了不同浓度的CTAB溶液中的N-CH₃质子的本征横向弛豫时间（T₂本征）和化学交换速率k_ex,发现k_ex与T₂本征和自扩散系数D一样,在临界胶束浓度（CMC）附近发生突变. 这个突变反映了CTAB分子在从单体到胶束的转变过程中其动力学特性发生了改变.      

Study of surface and solution properties of gemini-conventional surfactant mixtures and their effects on solubilization of polycyclic aromatic hydrocarbons

The aqueous solubility enhancement of the polycyclic aromatic hydrocarbons (PAHs) naphthalene, anthracene and pyrene by micellar solutions of single gemini surfactant hexanediyl-1,6-bis(dimethylcetylammonium bromide) (G6) and its mixtures with cationic cetyltrimethylammonium bromide (CTAB), anionic sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and nonioinic polyoxyethylene (20) cetyl ether (Brij 58) have been investigated. Above the cmc, maximum solubilization occurs in the Brij 58 surfactant micelles whereas the solubilization is least in presence of AOT. The PAHs are solubilized synergistically in mixed gemini-conventional surfactant solutions, which is attributed to the formation of mixed micelles, their lower cmc values, and the increase of the solvents' molar solubilization ratios or micellar partition coefficients because of the lower polarity of the mixed micelles.     

Mixed micellization study of ibuprofen (sodium salt) and cationic surfactant (conventional as well as gemini)

Herein, we have studied the interaction between cationic surfactant (conventional [myristyltrimethylammonium bromide, MTAB] as well as gemini surfactant 1, 4‐butanediyl‐α, ω‐bis(dimethyltetradecylammonium bromide) (14‐4‐14)) and anti‐inflammatory sodium salt of ibuprofen (IBU) drug in aqueous solutions by using tensiometry method at 298.15 K. The means of the interaction of drugs by added foreign materials is of paramount importance in the drug delivery. Ibuprofen is used for the relief of pain, fever, and swelling. From this study we have evaluated different parameters, for example, critical micelle concentration (cmc), micellar mole fraction of mixed micelles/mixed interface (X₁^m/X₁^σ), micellar/surface interaction parameter (β^m/β^σ), activity coefficients (f₁^m/f₁^σ and f₂^m/f₂^σ) of the mixed micelles/mixed interface, excess Gibbs free energy of mixed monolayer/mixed micelle formation ( $\mathrm{\Delta }{G}_{\mathrm{ex}}^{\mathrm{\sigma }}$/ $\mathrm{\Delta }{G}_{\mathrm{ex}}^{\mathrm{m}}$), surface excess concentration (Γ_max) etc. and discussed in detail. The micellar interaction parameter (β^m) was determined from the critical micelle concentration values of the pure surfactant (MTAB/14‐4‐14) and IBU (cmc₁ and cmc₂) and the mixed system (cmc) using the Rubingh's model. In addition to this, various other parameters such as packing parameters of amphiphiles in the micelles (P), volume contribution of the hydrophobic chain (V₀), and its effective length (l_c), have also been calculated. The value of micellar mole fraction ( $X_1^{\mathrm{m}}$) is found to be more for IBU + 14‐4‐14 mixtures as compared to IBU + MTAB mixtures at lower mole fraction and vice versa at a higher mole fraction of surfactant. The ΔG^o_m and ΔG^o_ads values for all studied systems were found out to be negative, ie, micellization, as well as adsorption processes, are found to be energetically favorable.     

Effect of glycyl dipeptides on the micellar behavior of gemini surfactant: A conductometric and fluorescence spectroscopic study

The effect of glycyl dipeptides (glycylglycine, glycyl-L-valine, and glycyl-L-leucine) on the micellar properties of gemini surfactant pentamethylene-1,5-bis(dodecyldimethylammonium bromide) (12-5-12) has been investigated by means of conductivity and fluorescence spectroscopy. The results obtained from conductivity show that the effect of glycyl dipeptides depends upon their nature and concentration, as well as the temperature. The values of critical micelle concentration (cmc) of 12-5-12 have been estimated in water + glycyl dipeptide media at various concentrations of dipeptide in the 293.15-318.15 K temperature range at 5 K intervals. From cmc values, it is observed that the micellization tendency of the surfactant increases in the presence of glycyl dipeptides. Thermodynamic parameters (ΔG_m^o, ΔH_m^o, and ΔS_m^o) of micellization of 12-5-12 in aqueous glycyl dipeptide solutions have been obtained by applying the mass action model and an enthalpy-entropy compensation effect was observed. The pyrene fluorescence spectra were used to study the change of micropolarity produced by the interaction of 12-5-12 with glycyl dipeptides, and the aggregation behavior of 12-5-12.     

Determination of the partition coefficients of the nonionic detergent C12E7 between lipid-detergent mixed membranes and water by means of Laurdan fluorescence spectroscopy

The membrane-water partition coefficient of the detergent C₁₂E₇ between water and C₁₂E₇/POPC mixed membranes has been determined by means of steady-state fluorescence spectroscopy. The emission spectra of the fluorescent probe Laurdan were used as an indicator of membrane composition at different membrane concentrations in the sample. The partition coefficient expressed as the ratio of the mole fractions of the detergent in the membrane and water phases is about 6^*10⁵ at low molar ratios of C₁₂E₇/POPC (R _c ) and decreases rapidly with increasingR _c . The limiting detergent content of the lamellar phase (R _c ^* >0.8) is indicated by a minimum ofP(R _c ).     

维生素C对菲醌三重激发态的淬灭机理及动力学研究

用时间分辨电子自旋共振技术研究了乙二醇(EG)均相溶液和反胶束溶液中抗氧化剂维生素C(VC)对菲醌(PAQ)分子激发三重态³PAQ*的淬灭反应．利用反胶束模拟生物细胞和组织的生理环境．光解PAQ/EG-H₂O均相溶液,³PAQ*与溶剂分子EG之间发生氢转移反应．当体系中加入VC后,³PAQ*不仅从EG上夺氢,还从VC上夺氢,VC对³PAQ*的淬灭速率常数为1.409×10⁸ L/(mol·s), 反应受扩散控制． 在CTAB/EG-H₂O和AOT/EG-H₂O反胶束溶液中,³PAQ*和VC之间的夺氢反应发生在反胶束的水/油界面附近,³PAQ*扩散到油/水界面的过程降低了反应的速率．对于TX-100/EG-H₂O反胶束溶液, 由于PAQ增溶于亲水的聚氧乙烯链中,VC对³PAQ*的淬灭速率常数比CTAB/EG-H₂O和AOT/EG-H₂O反胶束中的都大,甚至比EG-H₂O均相溶液中的也略大．很强的VC负离子自由基As^-的CIDEP信号来源于³PAQ*与VC之间发生抽氢反应过程中的三重态机理自旋极化转移