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.     

C_(12)-s-C_(12)·2Br和C_(12)E_n混合水溶液的胶团化行为

季铵盐二聚表面活性剂C12-s-C12·2Br(s=2、3、4、6)和非离子表面活性剂C12E10或C12E23在水溶液中生成混合胶团.其临界胶团总浓度cmcT值介于二元复配体系中各组分的临界胶团浓度cmc01和cmc02之间.当添加少量非离子型表面活性剂(在水溶液中的摩尔分数α2=0.1)时,混合胶团中C12E10或C12E23的摩尔分数均已超过0.35;随着溶液中非离子型表面活性剂含量的增大,混合胶团中逐渐以C12E10或C12E23成分为主.     

C12-s-C12·2Br和C12En混合水溶液的胶团化行为

季铵盐二聚表面活性剂C12-s-C12@2Br(s=2、3、4、6)和非离子表面活性剂C12E10或C12E23在水溶液中生成混合胶团.其临界胶团总浓度cmcT值介于二元复配体系中各组分的临界胶团浓度和之间.当添加少量非离子型表面活性剂(在水溶液中的摩尔分数α2=0.1)时,混合胶团中C12E10或C12E23的摩尔分数均已超过0.35;随着溶液中非离子型表面活性剂含量的增大,混合胶团中逐渐以C12E10或C12E23成分为主.     

C12-s-C12•2Br和C12En混合水溶液的胶团化行为

季铵盐二聚表面活性剂C12 s C12•2Br（s=2、3、4、6）和非离子表面活性剂C12E10或C12E23在水溶液中生成混合胶团.其临界胶团总浓度cmcT值介于二元复配体系中各组分的临界胶团浓度和之间.当添加少量非离子型表面活性剂（在水溶液中的摩尔分数α2=0.1）时,混合胶团中C12E10或C12E23的摩尔分数均已超过0.35;随着溶液中非离子型表面活性剂含量的增大,混合胶团中逐渐以C12E10或C12E23成分为主.     

庚烷中C12-EOx-C12•2Br反胶团的形成

在助表面活性剂正己醇存在下, 季铵盐Gemini表面活性剂C12-EOx-C12•2Br(x=1, 2, 3)在正庚烷中形成了反胶团. 以碘光谱法测定了临界反胶团浓度(cmch), 该值小于它们在水中形成正胶团时的临界浓度(cmcaq), 但两者随x的变化规律一致, 均呈单调增长. 反胶团饱和增溶水量随x增加或温度升高而增大.     

Gemini阳离子表面活性剂在水溶液中胶团化行为的温度效 应与焓、熵补偿

测定了Cemini阳离子表面活性剂C~m-----s-----C~m·2Br(m=8,10,12,;s=2,6及m=12;s=3,4)水溶液的电导,从电导(k)～表面活性剂浓度(c)曲线的转折点可求得临界胶团浓度cmc.实验发现,Gemini阳离子表面活性剂的胶团化倾向明显强于其“单体分子”)即单离子头基单烷烃链表面活性剂)。根据质量作用模型计算了胶经过程的吉布氏能、焓和熵的改变。结果表明Gemini表面活性剂聚集机理和其对应的“单体分子”类似,主要来自熵驱动。所有的焓/熵补偿图均呈现良好的线性关系,补偿直线在γ轴的截距随s减小而变小,这意味着具有较小s的Gemini表面活性剂倾向于生成稳定的胶团。     

季铵盐二聚表面活性剂C12-S2-C12·2Br复配体系在氯仿中形成反胶团的增溶水状态

采用近红外光谱技术,研究了季铵盐Gemini表面活性剂C12-S2-C12.2Br/氯仿体系中反胶团的增溶水状态,使用Peakfit解峰技术,将水的近红外光谱分为3个亚带,分别对应分散于溶剂中的水、反胶团中的类似本体水和结合水。将以上3种状态的水换算成每个表面活性剂分子对应的各种状态水分子数,即分散在溶剂中的水ns、类似本体水nf和结合水nb。向C12-S2-C12.2Br/氯仿体系中加入不同头基的离子型表面活性剂十二烷基三甲(乙)基溴化铵(DTAB、DTEB),发现随着添加剂摩尔分数αA的增大,ns和nb增大,nf减小。加入非离子表面活性剂聚乙二醇辛基苯基醚(OP-10),随着αA的增大ns减小,nb增大,nf略有增大趋势。可见加入表面活性剂头基的大小、所带电荷以及亲水性等均会对反胶团的增溶水能力和状态产生影响。     

连接基团链长度对季铵盐二聚表面活性剂C12-s-C12·2Br在水溶液中胶团化行为的影响

用电导法、稳态荧光法和粘度法研究了二聚表面活性剂C12-s-C12*2Br分子中的连接基团链长度(s=2, 3, 4, 6)对其在水溶液中聚集行为的影响. 实验发现, C12-s-C12*2Br的胶团生成能力远比其单体C12TABr强得多, 前者cmc值较后者降低一个数量级. 胶团聚集数N随表面活性剂浓度c的增大而增大, 其中当s=2时的N值在c=7.7 mmol/L后开始急剧增大. 计算结果表明, 此时胶团形状发生了明显变化, 形成了椭球形的胶团. 粘度测定结果也证实了这一点.     

C12-s-C12•2Br在正庚烷中反胶团形成及增溶水特性

在助表面活性剂正己醇存在下, 季铵盐Gemini表面活性剂C12-s-C12•2Br(s=2、3、4、5、6、8、12)在正庚烷中形成了反胶团. 以水增溶法测定了临界反胶团浓度cmcw, 这些cmcw均分别小于它们在水中生成正胶团的临界浓度cmcaq. cmcw随s的变化规律与cmcaq随s的变化规律类似, 在s=4时出现极大值. 由水增溶法和电导法获得的反胶团饱和增溶水量(mw或mc)约在s=5时出现最大值. 这些现象被归结为联接链构型的变化.     

荧光探针法测定Gemini表面活性剂C12-2-En-C12·2Br的临界预胶团浓度

以芘丁酸(PBA)为荧光探针测定了30℃时季铵盐Gemini表面活性剂C12-2 -En-C12·2Br水溶液的临界预胶团浓度(cpc)分别为0.029 5(n =1)、0.037 3(n =2)和0.050 1(n=3)mmol/L.结果表明,与通常方法(例如电导等)相比,荧光探针方法能更灵敏地反映二聚表面活性剂的预...     

C12-s-C12•2Br和己醇混合水溶液的胶团化行为

己醇的加入使C12-s-C12•2Br（s=3,4,6）的临界胶团浓度cmc降低,s越大其影响也越显著.己醇参与组成了混合胶团,当添加的己醇量相同时,它在混合胶团中的摩尔分数几乎一样.混合胶团表面反离子解离度随己醇浓度增大而增大.     

The effect of added alcohols on the micellization process of sodium 8-phenyloctanoate

¹H NMR chemical shifts were examined for mixtures of sodium 8-phenyloctanoate (Na-ω-PhOct) in deuterated aqueous solutions of varying compositions of ethoxylated alcohols. In addition, diffusion-oriented spectroscopy experiments (DOSY) were performed on selected compositions to obtain the diffusion coefficients of the ethoxylated alcohols in the mixed micelles. As expected, the alcohol/surfactant systems exhibit behavior typical to that of an anionic surfactant/alcohol system, in that the critical micellar concentrations and aggregation numbers decrease with increasing alcohol concentration in the mixed solvent. The ¹H NMR aromatic solute induced shifts (ASIS effects) on the alcohol and surfactant protons give significant information on the locations of the alcohol groups in the mixed micelle. All these results are interpreted in terms of the structure of the alcohol/surfactant systems as a function of their composition.     

SDS对SB3-12胶束表面电荷密度的调控作用及对药物增溶的影响

两性离子甜菜碱表面活性剂(SB3-12)胶束具有较好的生物相容性,由于相反电荷的极性头之间具有静电中和作用,胶束表面具有小的负电荷密度。当加入阴离子的十二烷基硫酸钠(SDS)以后,负离子SD-与SB3-12胶束极性区内层季铵正电荷的静电中和作用,能连续地调节胶束表面磺酸基的负电荷密度,这有利于对药物分子的选择性增溶和调节在生理条件下的药物的输送。等温滴定量热(ITC)研究发现SB3-12和SDS有强的协同效应,混合临界胶束浓度(CMC)和胶束化焓明显降低,并得到两者协同效应的弱静电作用机理。当模型药物分子芦丁(Rutin)与SB3-12/SDS混合胶束作用时,芦丁7位羟基的氢解离后的阴离子与SDS共同作用于SB3-12形成混合胶束。UV-Vis吸收光谱和~1H NMR谱研究发现,在SB3-12胶束中,芦丁分子的A环位于季铵阳离子附近,B环位于两个相反电荷之间的弱极性区域。在SDS胶束中,B环位于栅栏层,而A环和二糖暴露于水相侧。在混合胶束中,随着SDS摩尔分数增加,对A环的静电吸引变弱。离子表面活性剂对两性离子表面活性剂胶束表面电荷密度的调节作用,本质上是对胶束极性区域的物理及化学性质的微调,进而实现对药物的可控增溶。     

Solution properties of mixed surfactant systems (IV)

Electric properties of mixed anionic-nonionic surfactant systems in aqueous solutions above the CMC have been studied in terms of pNa values, electrical conductivities, and dielectric constants; these systems are sodium 3, 6, 9-trioxaicosanoate (ECL) — alkyl polyoxyethylene ethers (C_mPOE; m=12, 14, 16, and 18). The degree of ionic dissociation of mixed micelle increases with increasing the number of carbon atoms of the alkyl group in the nonionic surfactant. The electrical conductivity increases with increasing the alkyl chain length in the nonionic surfactant, in spite of the increase of the activation energy for conduction. The size of mixed micelles also increases with increasing alkyl chain length. This may be attributed to the fact that the mixed micelle is formed more easily by a nonionic surfactant including long alkyl chains than for one having shorter alkyl chains.     

Fading phenomena of azo oil dye in anionic-nonionic surfactant solutions III. The effect of solubilizates on the fading behavior of azo oil dye in mixed surfactant systems

The effects of solubilizates on the fading behavior of 4-phenylazo-1-naphthol (4-OH) in aqueous solutions of anionic-nonionic mixed surfactant systems are described; the systems studied are sodium dodecyl sulfate (SDS) — octadecyl poly(oxyethylene) ethers (C₁₈POE₂₀). The fading rate of 4-OH in the mixed solution was independent of the addition of octane. By adding octanoic acid, the rate became faster. On the other hand, the 1-octanol slowed the rate. The fading speed of 4-OH decreased as the concentration of the alcohol and the number of carbon atoms in the alcohol molecule, used as a solubilizate, increased. The sizes of mixed micelles penetrated by the solubilizate were dependent on the kind of oily materials and on the alkyl chain lengths in the molecules of normal higher alcohols. Relative viscosities and effective specific volumes in the mixed micellar solutions increased with the increase in the concentration of 1-octanol and octanoic acid, and with increasing the number of alkyl groups in the alcohol molecule. The effect of solubilizates on the fading behavior of 4-OH was found to be dependent on the differences in their solubilization sites in mixed micelles. A solubilizate with a strong polar group supported a hydrophilic-hydrophilic interaction, whereas one including a weak polar group did not.     

Wormlike micelles of polyoxyethylene alkyl ether mixtures C10E5 + C14E5 and C14E5 + C14E7: hydrophobic and hydrophilic chain length dependence of the micellar characteristics

The wormlike micelles formed with the binary mixtures of surfactant polyoxyethylene alkyl ethers (CiEj), C10E5 + C14E5 (Mix1) and C14E5 + C14E7 (Mix2), were characterized by static (SLS) and dynamic light scattering (DLS) experiments. The SLS results have been analyzed with the aid of the light scattering theory for micelle solutions, thereby yielding the molar mass Mw(c) as a function of c along with the cross-sectional diameter d of the micelle. The observed Kc/DeltaR0 as a function of c, the mean-square radius of gyration (S2) and the hydrodynamic radius RH as functions of Mw have been well described by the theories for the wormlike spherocylinder model. It has been found that the micellar length increases with increasing concentration c or with raising temperature T irrespective of the composition of the surfactant mixtures. The length of the Mix1 and Mix2 micelles at fixed c and T steeply increases with increasing weight fraction wt of C14E5 in both of the surfactant mixtures, implying that the micelles greatly grow in length when the surfactant component with longer alkyl group or with shorter oxyethylene group increases in the mixture. The results are in line with the findings for the micelles of the single surfactant systems where the CiEj micelles grow in length to a greater extent for larger i and smaller j. Although the values of d and the spacing s between the adjacent surfactant molecules on the micellar surface do not significantly vary with composition of the surfactant mixture, the stiffness parameter lambda-1 remarkably decreases with wt in both Mix1 and Mix2 micelles, indicating that the stiffness of the micelle is controlled by the relative strength of the repulsive force due to the hydrophilic interactions between oxyethylene groups to the attractive one due to the hydrophobic interactions between alkyl groups among the surfactant molecules.     

Properties of mixed micelles of cationic gemini surfactants and nonionic surfactant triton X-100: effects of the surfactant composition and the spacer length

The mixed micelles of cationic gemini surfactants C12C(S)C12Br2 (S=3, 6, and 12) with the nonionic surfactant Triton X-100 (TX100) have been studied by steady-state fluorescence, time-resolved fluorescence quenching, electrophoretic light scattering, and electron spin resonance. Both the surfactant composition and the spacer length are found to influence the properties of mixed micelles markedly. The total aggregation number of alkyl chains per micelle (N(T)) goes through a minimum at X(TX100)=0.8. Meanwhile, the micropolarity of the mixed micelles decreases with increasing X(TX100), while the microviscosity increases. The presence of minimum in N(T) is explained in terms of the competition of the reduction of electrostatic repulsion between headgroups of cationic gemini surfactant with the enhancement of steric repulsion between hydrophilic headgroups of TX100 caused by the addition of TX100. The variations of micropolarity and microviscosity indicate that the incorporation of TX100 to the gemini surfactants leads to a more compact and hydrophobic micellar structure. Moreover, for the C12C3C12Br2/TX100 mixed micelle containing C12C3C12Br2 with a shorter spacer, the more pronounced decrease of N(T) at X(TX100) lower than 0.8 may be attributed to the larger steric repulsion between headgroups of TX100. Meanwhile, the increase of microviscosity and the decrease of micropolarity are more marked for the C12C12C12Br2/TX100 mixed micelle, owing to the looped conformation of the longer spacer of C12C12C12Br2.     

Solvation dynamics in aqueous anionic and cationic micelle solutions: sodium alkyl sulfate and alkyltrimethylammonium bromide

Solvation dynamics of the fluorescence probe, coumarin 102, in anionic surfactant, sodium alkyl sulfate (C(n)H(2n+1)SO(4)Na; n = 8, 10, 12, and 14), and cationic surfactant, alkyltrimethylammonium bromide (C(n)H(2n+1)N(CH(3))(3)Br; n = 10, 12, 14, and 16), micelle solutions have been investigated by a picosecond streak camera system. The solvation dynamics in the time range of 10(-10)-10(-8) s is characterized by a biexponential function. The faster solvation time constants are about 110-160 ps for both anionic and cationic micelle solutions, and the slower solvation time constants for sodium alkyl sulfate and alkyltrimethylammonium bromide micelle solutions are about 1.2-2.6 ns and 450-740 ps, respectively. Both the faster and the slower solvation times become slower with longer alkyl chain surfactant micelles. The alkyl-chain-length dependence of the solvation dynamics in both sodium alkyl sulfate and alkyltrimethylammonium bromide micelles can be attributed to the variation of the micellar surface density of the polar headgroup by the change of the alkyl chain length. The slower solvation time constants of sodium alkyl sulfate micelle solutions are about 3.5 times slower than those of alkyltrimethylammonium bromide micelle solutions for the same alkyl-chain-length surfactants. The interaction energies of the geometry optimized mimic clusters (H(2)O-C(2)H(5)SO(4)(-) and H(2)O-C(2)H(5)N(CH(3))(3)(+)) have been estimated by the density functional theory calculations to understand the interaction strengths between water and alkyl sulfate and alkyltrimethylammonium headgroups. The difference of the slower solvation time constants between sodium alkyl sulfate and alkyltrimethylammonium bromide micelle solutions arises likely from their different specific interactions.