分子内扭转电荷转移探针DMABN测定表面活性剂水溶液的临界胶团浓度

以对二甲氨基苯甲腈(DMABN)为探针, 测定它在表面活性剂(C12TABr、SDS、C12E23、C12-3-12·2Br)水溶液中的第二重荧光强度(Ia)和对应的特征波长(λa)对表面活性剂浓度(c)曲线, 由Ia-c 曲线的转折点或λa-c曲线对应的一阶导数极小点可以获得临界胶团浓度(cmc). 由于C12-3-C12·2Br在水溶液中强烈聚集, 利用λa-c曲线还可以获得其胶团结构松散度的信息.     

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.     

非理想二元表面活性剂复配增效理论的进一步研究

在Rubingh与Rosen 提出非理想二元表面活性剂复配增效条件基础上,利用相分离模型和正规溶液理论,导出了体系降低表面张力的能力增效条件βs-βm<0,及最佳摩尔分数α1*、最低表面张力γ*cmc12和γ*cmc处对应的临界胶束浓度cmc*12.通过作三条γ～logc曲线或两条γ～logc曲线加上一个cmc值的方法,对C12NMe3Br～C12SO4Na、 C12NMe3Br～C8SO4N两种复配体系进行验证,计算结果与实验结果相符.     

乙醇/水混合溶剂中Gemini表面活性剂的表面性质

通过对Gemini表面活性剂12-s-12 (Et)(s=4, 6, 8, 10, 12)体系在乙醇/水混合溶剂中的表面张力曲线的测定, 对该体系的表面性质进行了研究. 发现随乙醇/水比例变化, Gemini各种表面化学性质, 如临界胶束浓度(cmc)、表面张力(γcmc)、饱和吸附量(Γmax)和最小分子占有面积(Amin)等的变化规律. 拓展了Gemini表面活性剂在混合溶剂中表面吸附的研究.     

稳态荧光探针法测定三聚季铵盐表面活性剂的胶束聚集数

以芘为荧光探针, 十六烷基氯化吡啶(CPC)为猝灭剂, 以芘的饱和水溶液为溶剂配制表面活性剂溶液, 根据芘的荧光强度之比I1/I3随表面活性剂水溶液浓度的变化, 测定了三聚季铵盐表面活性剂CTTTA的cmc值, 测定值与表面张力法测定的cmc值一致；当猝灭剂CPC的浓度取0.1~0.3 mmol·L-1范围时, 用稳态荧光探针法测定了CTTTA的胶束聚集数. 实验数据表明, 表面活性剂溶液浓度为6~10倍cmc时, 胶束聚集数N随表面活性剂浓度增大而线性增大, 并用外推法得到CTTTA的临界胶束聚集数.     

稳态荧光探针法研究对-烷基-苄基聚氧乙烯醚羧酸甜菜碱的聚集行为

利用荧光探针法和表面张力法测定了一类疏水基中含有苯基的新型甜菜碱两性离子表面活性剂对-烷基-苄基聚氧乙烯醚羧酸甜菜碱(ABECB)的临界胶团浓度(cmc)、胶团微极性和表面张力(γ_cmc).研究结果表明,荧光探针(芘)法可用来测定这类表面活性剂的临界胶团浓度(cmc),且测定结果与表面张力法(吊片法)接近;ABECB具有较低的cmc和γ_cmc值,表明此类表面活性剂具有优良的表面活性; 胶团的微极性随着疏水链长的增大而略微减小,氧乙烯(EO)单元数的增大对ABECB胶团核内的微极性影响不明显.     

十六烷基二苯醚二磺酸钠分子有序聚集体的研究

采用芘为荧光探针、二苯甲酮为猝灭剂，以分子荧光探针法首次测定了由刚性基团联接的特殊双亲水基型阴离子表面活性剂——十六烷基二苯醚二磺酸钠(C16-MADS)的胶束聚集数(Nm)，并考察了表面活性剂浓度、无机盐浓度和温度对Nm的影响。结果表明，表面活性剂的浓度必须高于临界胶束浓度(cmc)一个数量级时，才能测定出较为合适的Nm；随着C16-MADS浓度的增大，Nm增大，胶束内核的微极性变小；而温度对Nm的影响极小。与传统的单亲水基阴离子表面活性剂相比，C16-MADS的有序聚集体表现出许多不同之处，如Nm仅为传统的单亲水基阴离子表面活性剂胶束聚集数的一半，无机盐浓度对Nm的影响极小，胶束内核的微极性明显增大。     

氨基酸型表面活性剂烷基二羧酸钠的结构对表面活性、自聚集行为及润湿性能的影响

本文合成了3个氨基酸型表面活性剂:十二烷基甘氨酸钠(C12GlyNa)、十二烷基氨基丙二酸钠(C12MalNa2)和十二烷基谷氨酸钠(C12GluNa2),用表面张力法、荧光探针法及接触角测量,研究了它们的分子结构对表面活性、自聚集行为以及对方解石润湿性能的影响。结果表明,当增加一个羧基后,氨基酸型表面活性剂的临界胶团浓度(cmc)和最低表面张力(γ_(cmc))增大,饱和吸附量(Г_(max))和胶团聚集数减小,降低表面张力的效率(pC_(20))降低,但在方解石表面的接触角变化较小。与C12MalNa2相比,在两个羧基之间增加一个亚甲基的C12GluNa2,其最低表面张力(γ_(cmc))变化很小,但cmc和Г_(max)更小,A_(min)更大,在方解石表面的最大接触角增大,对方解石的润湿性能降低。     

不等链长的碳氟、碳氢正负离子表面活性剂混合体系的表面活性

研究了全氟辛酸钠与溴化十四烷基三甲铵混合水溶液的表面活性. 测定了不同比例混合物水溶液的表面张力-浓度曲线, 得出临界胶团浓度(cmc)及监 界胶团浓度时的溶液表面张力(γcmc)值. 应用Gibbs吸附公式及吸附层中两表面活性剂分子相互作用参数法求出表面总吸附量、吸附层组成及两表面活性剂分别吸附量等. 指示此吸附层具有多分子层性质. 这可能是碳氢、碳氟正负离子混合体系的特点.     

1-萘胺探针研究Gemini表面活性剂的胶团性质

1-萘胺是一种具有分子内电荷转移特征的探针。利用它的荧光特征波长对环境极性的敏感性，其 logC曲线出现了2个浓度相距较大的转折点，第一个转折点对应临界胶团浓度cmc，第二个转折点Ccm则表征胶团结构达到较为密实的临界点。实验发现，Gemini表面活性剂在cmc时仅生成聚集数N较小的聚集体，在浓度从cmc增大至Ccm的区间内，N急剧增大。     

Determination of the Critical Micelle Concentration of Surfactant in Aqueous Solution by Twisted Intramolecular Charge Transfer Probe DMABN

With p-N,N-dimethylaminobenzonitrile (DMABN) as a probe, the variations of the intensity of its second fluorescence emission (I_a) and the corresponding characteristic wavelength (λ_a) with the surfactant concentration (c), here the examined surfactants (C₁₂TABr, SDS, C₁₂E₂₃, and C₁₂-3-C₁₂·2Br), were measured by Hitachi F4500 fluorescence spectrophotometer. The results showed that both the break points on the I_a–c curve and the minimum of the derivative variation corresponding to the λ_a–c curve agreed very well with the critical micelle concentration (cmc) of the surfactant in aqueous solution as measured by surface tension technique. Due to strong aggregation of C₁₂-3-C₁₂·2Br in aqueous solution, the information about loose micellar structure could be obtained by its λ_a–c curve.     

Solution properties of amino acid-type new surfactant

The solution properties of an amino acid-type new surfactant, N-[3-lauryloxy-2-hydroxypropyl]-L-arginine L-glutamate (C12HEA-Glu), were examined by means of pK(a), surface tension, light scattering and fluorescence measurements. The dissociation state of C12HEA-Glu was changed by varying pH of the aqueous solution. The critical micelle concentration (cmc) of aqueous solution of C12HEA-Glu was lowest at pH 5.6 and the cmc increased with decreasing pH. The aggregation number of C12HEA-Glu micelles was largest at pH 5.6 and decreased with decreasing pH. The surface tension-concentration curve for C12HEA-Glu in water (non-buffered solution) showed a minimum. This is considered to be due to the coexistence of a trace species and a main species of C12HEA-Glu with various dissociation states since the pH of aqueous solution of C12HEA-Glu changes with the concentration of C12HEA-Glu. The micropolarity in the micelles of C12HEA-Glu was almost independent of pH, while the microfluidity in the micelles increased with increasing pH.     

Characterization of mixed non-ionic surfactants n-octyl-β-D-thioglucoside and octaethylene-glycol monododecyl ether: micellization and microstructure

Mixed micelles of n-octyl-β-D-thioglucoside (OTG) and octaethylene-glycol monododecyl ether (C(12)E(8)), two non-ionic surfactants belonging to the alkyl glucosides and polyoxyethylene alkyl ether families, respectively, were investigated by using light scattering and fluorescence probe techniques. From the determination of the critical micelle concentration (cmc), by the well-established pyrene 1:3 ratio method, it was found that the mixed system behaves ideally, the micellization process being clearly controlled by the ethoxylated surfactant. The micellar hydrodynamic radius as a function of temperature, composition and concentration was obtained by dynamic light scattering measurements. It was observed that the micellar size increases with temperature, this growth being more pronounced as the relative proportion of the ethoxylated surfactant was increased. The behavior of the micellar size with the total surfactant concentration was also found to be dependent on temperature and composition. The clouding temperature, characteristic of the ethoxylated surfactants, was increased with the addition of the sugar surfactant. Lastly, possible structural changes in the micellar palisade layer were examined by steady-state fluorescence anisotropy in conjunction with time-resolved fluorescence studies with the hydrophobic probe coumarin 6 (C6). The obtained results indicate that the participation of the ethoxylated surfactant induces a slightly more polar palisade layer, whereas the probe carries out a faster rotational reorientation as a result of a less compact environment. All these observations were attributed to the different structure of the head groups of both surfactants and, as a consequence, to their different hydration.     

Surface and micellar properties of new nonionic gemini aldonamide-type surfactants

A new group of gemini aldonamide-type surfactants-N,N'-bisalkyl-N,N'-bis[(3-gluconylamide)propyl]ethylenediamines, N,N'-bisdodecyl-N,N'-bis[(3-glucoheptonylamide)propyl]ethylenediamine, and N,N'-bisalkyl-N,N'-bis[(3-lactobionylamide)propyl]ethylenediamines, (alkyl: n-C(8)H(17), n-C(12)H(25)), were synthesized and characterized. The surface properties, such as surface excess concentration, Gamma(cmc), surface area demand per molecule, A(min), efficiency in surface tension reduction, pC(20), the effectiveness of surface tension reduction, gamma(cmc), critical micelle concentration, cmc, and a measure of the tendency of the surfactant to adsorb at the aqueous/air interface relative to its tendency to form micelles in the bulk surfactant solution, cmc/C(20), and standard free energy of micellization, DeltaG(mic)(0), have been obtained by means of surface tension measurements. The standard fluorescence shift technique using PRODAN as a probe provide confirmation of the cmc values by an alternative method. Additionally, the micellar properties for the concentration near above the cmc have been characterized by the aggregation number, N(agg). The presence of the dimeric segments with the aldonamide hydrophilic units in the surfactant molecule is found to be the source of their unusual physicochemical behavior. They are very efficient at adsorbing at the free surface and at forming micelles in water. Their critical micelle concentration values are remarkably low. They reveal remarkably low A(min) values in relation to conventional nonionic surfactants, which is unexpected from the molecular dimensions for the molecule but which is possible if one assumes some type of multilayer structure or a coherent interfacial film.     

New fluorescence method for the determination of the critical micelle concentration by photosensitive monoazacryptand derivatives

A novel fluorescence method for the determination of the critical micelle concentration (cmc) is reported. The cmc values of nonionic and anionic surfactants were evaluated utilizing a photosensitive monoazacryptand-Ba2+ complex, whose fluorescence intensity is sensitively changed by environmental conditions based on the photoinduced electron transfer (PET) mechanism as a fluorescent probe (PET method). Based on a comparison of the cmc values obtained by the PET method versus those obtained by conventional fluorescence-based methods as well as the values reported in the literature, one can conclude that the PET method is useful for the cmc determination. In particular, the PET method was more effective for the cmc determination of nonionic surfactants with very low cmc values (< 10(-5) M) than any other fluorescence-based method. In the cases of anionic surfactants, the PET method revealed the formation of the premicellar aggregates comprised of surfactant molecules and fluorescent probes below the cmc. Moreover, the hydrophobicity around the monoazacryptand-Ba2+ complex incorporated into various nonionic surfactant micelles was evaluated by this PET method.     

Synthesis and properties of a novel class of gemini pyridinium surfactants

A novel class of gemini pyridinium surfactants with a four-methylene spacer group was synthesized, and their surface-active properties and interactions with polyacrylamide (PAM) were evaluated by surface tension, fluorescence, and viscosity measurements. A comparison between the gemini pyridinium surfactants and their corresponding monomers was also made. The cmc's of gemini pyridinium surfactants are much lower than those of the corresponding monomeric surfactants. The C20 value is about one order of magnitude lower than that of corresponding monomers, and the longer the hydrophobic chains of the surfactants, the lower the cmc value. Surface tension measurements of the surfactant-PAM mixed systems show that the critical aggregation concentration (cac) value is much lower than the cmc value of the surfactant system alone. Viscosity measurements of the surfactant-PAM mixed systems show that the relative viscosity of the surfactant-PAM system decreased with increasing concentration of surfactant. Additionally, fluorescence measurements of the surfactant-PAM mixed system suggest the formation of surfactant-polymer aggregates, and the gemini pyridinium surfactant with longer hydrophobic chains have a stronger interaction with PAM, owing to the stronger hydrophobic interaction.     

Zwitterionic heterogemini surfactants containing ammonium and carboxylate headgroups. 1. Adsorption and micellization

Zwitterionic heterogemini surfactants with two hydrocarbon chains and two different hydrophilic groups, N,N-dimethyl-N-[2-(N'-alkyl-N'-beta-carboxypropanoylamino)ethyl]-1-alkylammonium bromides (2C(n)AmCa, where n represents the hydrocarbon chain lengths of 8, 10, 12, and 14), were synthesized by N,N-dimethylethylenediamine with alkyl bromide, followed by reaction with succinic anhydride. One of the hydrophilic groups is a carboxylate anion, and the other is an ammonium cation. Their physicochemical properties were characterized by measuring equilibrium and dynamic surface tension, fluorescence intensity of pyrene, and light-scattering intensity. A relationship between a logarithm of critical micelle concentration (cmc) and hydrocarbon chain length showed a linear decrease upon increasing chain length and then a departure from linearity at n = 14. This is due to the existence of premicellar aggregations at concentrations below the cmc for n = 14. The surface tension of 2C(n)AmCa reached 27-30 mN m(-1) at each cmc, indicating efficiencies typical of hydrocarbon chain surfactants. The adsorbing rate at the air/water interface became slow with an increase of the chain length. From the fluorescence intensity ratios of 373 and 384 nm using pyrene as a probe, for n = 8, 10, and 14, the pyrene was solubilized in surfactant micelles at around the cmc, whereas for n = 12 the pyrene was solubilized from a concentration of 10-fold the cmc. The scattering intensities by dynamic light scattering also increased from around these concentrations for each chain length, showing the formation of aggregates in solution.