正、负离子碳氟-碳氢表面活性剂混合水溶液的表面活性

1　前言碳氟表面活性剂是目前所有表面活性剂中表面活性最高的一类 ,具有很多碳氢表面活性剂无法取代的特殊用途[1] 。但是碳氟表面活性剂由于合成困难 ,价格昂贵 ,实际应用受到限大限制。研究表明 ,通过碳氟表面活性剂与碳氢表面活性剂的复配 ,有可能减少碳氟表面活性剂的用量而保持其表面活性 [1] 。在所有表面活性剂混合体系中 ,正、负离子表面活性剂混合体系具有最强的协同效应 [2 ] 。但由于正、负离子表面活性剂混合溶液一般在很低浓度即形成沉淀 ,对碳氟表面活性剂更是如此。因此目前有关碳氟—碳氢混合表面活性剂的研究主要集中在同…     

碳氟表面活性剂与碳氢表面活性剂混合水溶液的表面吸附和胶团形成——Ⅱ.全氟辛酸钠-十烷基硫酸钠体系

测定了不同摩尔比的全氟辛酸钠(7CFNa)-十烷基硫酸钠(C_(10)SNa)混合水溶液(加NaCl,恒定离子强度μ=0.1m)的表面张力和界面张力(正庚烷-水溶液界面张力)。由表(界)面张力-浓度关系求出混合体系的表(界)面吸附和临界胶团浓度(cmc)。结果表明:(1)7CFNa和C_(10)SNa在μ=0.1m的溶液中,cmc相近,两者表面活性相近;但7CFNa降低水表面张力的能力较强,在cmc时的表面张力可低达～23mNm~(-1)。因此,在混合溶液的表面上,7CFNa的表面活性较高,优先吸附于表面。对于各种摩尔比的混合溶液,7CF~-在表面层中的比例皆大于在溶液内部的比例。(2)正庚烷-水溶液界面上的吸附与表面吸附截然不同。7CF~-在界面吸附层中的比例低于溶液内部,表明其吸附能力比C_(10)S~-为弱。这是由于界面一边的正庚烷与C_(10)SNa碳氢链之间的作用大于与7CFNa碳氟链之间的作用。亦即碳氟链与碳氢链“互憎”作用在界面上的表现。(3)在不同摩尔比的混合溶液中,各组分的cmc接近一恒值,进一步说明混合溶液中存在碳氟链与碳氢链间的互憎作用,以致两种表面活性剂在混合溶液中(有过量无机盐时)基本上各自形成胶团。     

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.     

碳氟表面活性剂与碳氢表面活性剂混合水溶液的表面吸附和胶团形成 Ⅰ.全氟辛酸钠-溴化辛基三甲铵体系

测定了一系列不同比例的全氟辛酸钠(7CFNa)-溴化辛基三甲铵(C_8NBr)混合水溶液(μ=O.1mol·kg~(-1)的表面张力.自表面张力-浓度关系求出混合体系的cmc和溶液表面吸附;研究了混合溶液在油面上的铺展性能.结果表明:(1)混合体系的表面活性远高于单一的C_8NBr或7CFNa,两个组分在表面活性上相互促进;(2)混合溶液的总饱和吸附量(Γ_T)随7CFNa/C_8NBr摩尔比的减小而增加:自100/1时的4.7×10~(-10)mol·cm~(-2)增至1/300时的7.3×10~(-10)mol·cm~(-2)(相应的分子面积为22.7A~2).这主要是由于碳氟链的疏水性远较碳氢链为大(虽然后者碳原子数较多);(3)7CFNa-C_8NBr溶液的表面层有独特的结构.不同于一般正、负碳氢表面活性剂混合溶液.基于表面层吸附分子面积的计算结果,并考虑到碳氟链与碳氢链间的互憎作用及正、负电荷的相互吸引作用,提出表面吸附层可能为双分子层结构的假设;(4)混合溶液的极限表面张力很低(～15mNm~(-1)),溶液-正庚烷界面张力亦然(～O.4mNm~(-1));即使溶液浓度及7CFNa与C_8NBr之比相当小时亦如此.因此,这种稀水溶液能在正庚烷、汽油等油面上铺展成(水)膜,故此种碳氟、碳氢表面活性剂混合物可用作“轻水”灭火剂配方中极有效的成分.     

全氟辛酸钠与十二烷基三甲基溴化铵混合胶束微环境性质的NMR,ESR研究

应用表面张力法、NMR法和ESR法研究了全氟辛酸钠(SPFO)-十二烷基三甲基溴化铵(DTAB)混合体系水溶液胶束形成及混合胶束的微环境性质(微观粘度、微观极性等)。结果表明, 碳氟表面活性剂碳氟链和碳氢表面活性剂碳氢链之间具有强烈的相互作用, DTAB与SPFO在水溶液中形成混合胶束。DTAB与SPFO混合体系的表面活性高于单一的DTAB或SPFO, 混合体系cmc较单一的DTAB和SPFO低。DTAB与SPFO混合胶束的微观粘度较DTAB胶束的大, 而微观极性较DTAB的小。     

全氟辛酸钠与十二烷基三甲基溴化铵混合胶束微环境性质的NMR, ESR研究

应用表面张力法、NMR法和ESR法研究了全氟辛酸钠(SPFO)-十二烷基三甲基溴化铵(DTAB)混合体系水溶液胶束形成及混合胶束的微环境性质(微观粘度、微观极性等).结果表明,碳氟表面活性剂碳氟链和碳氢表面活性剂碳氢链之间具有强烈的相互作用,DTAB与SPFO在水溶液中形成混合胶束.DTAB与SPFO混合体系的表面活性高于单一的DTAB或SPFO,混合体系cmc较单一的DTAB和SPFO低.DTAB与SPFO混合胶束的微观粘度较DTAB胶束的大,而微观极性较DTAB的小.     

表面活性剂和四烷基溴化铵的复配 Ⅲ.四烷基溴化铵碳氢链长对离子型表面活性剂在气/液表面吸附行为的影响

本文考察了四烷基澳化铵(TAAB)碳氢链长对离子型表面活性剂SDS和DTAB在气/液表面吸附行为的影响.实验结果表明,与表面活性剂离子对应的添加剂反离子是影响其水溶液表面活性的主要因素,因而TAAB对SDS表现出明显的效应,对DTAB影响效果则和同浓度的NaBr类似.除了对表面活性离子头基电荷的静电屏蔽外,TAA+的碳氢基团和SD-碳氢链间还可能发生疏水相互作用,但后者受TAA+离子体积制约.TAAB对SDS在气/液表面吸附行为的影响是上述几个因素的综合作用结果.     

碳氟表面活性剂与碳氢表面活性剂混合水溶液的表面吸附与胶团形成(Ⅳ)——非离子-非离子体系

测定了25℃不同比例的C₁₀F₁₉O(C₂H₄O)₉H与C₈H₁₇C₆H₄O(C₂H₄O)₁₀H混合水溶液的表面张力,研究混合水溶液的表面性质与胶团形成。用两种不同方法计算在表面上的表面成份、分子之间相互作用参数(β_σ)。结果表明,在非离子型碳氟和碳氢表面活性剂混合水溶液中,两种表面活性剂基本上各自形成胶团;表面分子相互作用参数皆为正值;表明此混合体系中碳氟链与碳氢链之间互疏作用的存在。     

氧杂氟表面活性剂及其与同电性碳氢表面活性剂混合溶液的表面吸附和胶团形成

研究了四种氧杂氟表面活性及其与同电性直链碳氢表面活性剂混合体系的表面活性;考察了混合体系中的表面吸附和胶团形成现象.在吸附层中分子间有明显的互疏作用,在溶液中倾向于各自形成胶团.还讨论了反离子结合度不同对理想混合胶团的组成CMC的计算的影响,提出了一般的计算式,实验测得这些氧杂氟表面活性剂有较低的胶团反离子结合度.     

碳氟-碳氢表面活性剂混合水溶液在油面上铺展

本文研究RfCONH(CH2)3N(C2H5)2CH3I/CnH2n 1,COONa及RfCOONa/CmH2m 1N(CH3)3Br(Rf=F[CF(CF3)CF2O]2CF(CF3);n=7,8.11,13;m=8,10,12)两类正，负离子碳氟－碳氢表面活性剂混合水溶液在油面上的铺展及对油面的密封性能。研究表明在碳氟表面活性剂中加入异电性碳氢表面活性剂可大大降低碳氟表面活性剂水溶液的铺展浓度，也可使一些因素表面张力较高而不能铺展的碳氟表面活性剂水溶液在油面上铺展。在碳氟表面活性剂中加入异电性碳氢表面活性剂可提高水膜对油面的密封性。若在混合表面活性剂中加入黄原胶，水膜的密封性能更好。     

Synthesis and applications of surfactants containing fluorine

Syntheses and solution properties of novel fluorinated surfactants with branched tail, especially on anionic surfactants having two polyfluoroalkyl chains and on anionic surfactants having different hydrophobic chains (hybrid surfactants), are reviewed. For example, when the fluorocarbon chain length in the surfactants possessing two polyfluoroalkyl chains increases, the Krafft points and the area of surfactant molecule at the air-water interface increases, the critical micelle concentration decreases, but the degrees of ionic dissociation of micelle are almost the same. Moreover, the flocculation and redispersion abilities of these surfactants for dispersed magnetic particles in water are enhanced by an increase in the chain length. The hybrid surfactants are found to have the ability to considerably lower surface tension, and they can emulsify a ternary-component system of hydrocarbon/water/perfluoropolyether oil. Furthermore, some of the hybrid surfactants show anomalous solution properties and thermoresponsive viscoelasticity due to the assembly structure changes with increasing its concentration.     

Synthesis and Properties of New Tricephalic Tetrasiloxane Surfactants Containing Carbohydrate and Hydrocarbon Chain

A new family of tricephalic tetrasiloxane surfactants containing carbohydrate and hydrocarbon chain (SiC(n + 1)N-GA, in which n + 1 represents a hydrocarbon chain length of 1, 8, 12, 16), was synthesized using two-step method. Their structures were confirmed by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy (¹H NMR). Their surface activities and aggregation properties in aqueous solution were investigated by surface tension measurements, transmission electron microscopy, and dynamic light scattering. The results indicated that the critical micelle concentration (CMC) of these surfactants increased and the surface tension (γ_CMC) at the CMC decreased with an increase in the number of hydrocarbon chain, and they can self-assemble into spherical micelles with average diameters in the range from 5 to 200 nm, which are smaller than for single-headed surfactants.     

Interactions between cationic starch and anionic surfactants

The surface tensions and the phase equilibria of dilute aqueous cationic starch (CS)/surfactant systems were investigated. The degree of substitution of the CS varied from 0.014 to 0.772. The surfactants investigated were sodium dodecyl sulphate (SDS), potassium octanoate (KOct), potassium dodecanoate (KDod) and sodium oleate (NaOl). The concentrations of CS were 0.001, 0.01 and 0.1 w%.Critical association concentrations (cac) occur at surfactant concentrations well below the critical micelle concentrations of the surfactants, except for KOct, KDod and NaOl at the lowest CS concentrations investigated (0.001 w%). The surface tensions of CS/surfactant solutions decrease strongly already below the cac. This is attributed to the formation of surface active associates by ion condensation. Associative phase separation of gels formed by CS and surfactant takes place at extremely low concentrations when the surfactant/polymer charge ratio is somewhat larger than 1. The gel is higly viscous and contains 40–60% water, depending on the concentration of electrolyte, the surfactant hydrocarbon chain length and the nature of the polar head of the surfactant.The concentration at which the phase separation occurs decreases with increasing surfactant chain length and the concentration of simple electrolyte, factors that promote micelle formation. This indicates that the gels are formed by association of CS to surfactant micelles. When surfactant well in excess of charge equivalence is added, the gels dissolve because the CS/surfactant complexes acquire a high charge.     

The influence of chain length and electrolyte on the adsorption kinetics of cationic surfactants at the silica-aqueous solution interface

The equilibrium and kinetic aspects of the adsorption of alkyltrimethylammonium surfactants at the silica-aqueous solution interface have been investigated using optical reflectometry. The effect of added electrolyte, the length of the hydrocarbon chain, and of the counter- and co-ions has been elucidated. Increasing the length of the surfactant hydrocarbon chain results in the adsorption isotherm being displaced to lower concentrations. The adsorption kinetics indicate that above the cmc micelles are adsorbing directly to the surface and that as the chain length increases the hydrophobicity of the surfactant has a greater influence on the adsoption kinetics. While the addition of 10 mM KBr increases the CTAB maximal surface excess, there is no corresponding increase for the addition of 10 mM KCl to the CTAC system. This is attributed to the decreased binding efficiency of the chloride ion relative to the bromide ion. Variations in the co-ion species (Li, Na, K) have little effect on the adsorption rate and surface excess of CTAC up to a bulk electrolyte concentration of 10 mM. However, the rate of adsorption is increased in the presence of electrolyte. Slow secondary adsorption is seen over a range of concentrations for CTAC in the absence of electrolyte and importantly in the presence of LiCl; the origin of this slow adsorption is attributed to a structural barrier to adsorption.     

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.     

Competitive adsorption of surfactants at air/water interfaces

The zeta potential of an air bubble suspended in an aqueous solution of mixed fluorocarbon and hydrocarbon anionic surfactants is studied over a wide range of concentrations and mixture compositions. The zeta potential is related to surfactant ion adsorption. The two surfactants, which exhibit an antipathy manifested by micellar demixing, compete for surface sites. The total surfactant adsorption is reduced when both surfactants are present. Adsorption phenomena are closely correlated to the micellar phase diagram.     

Restructuring of hydrophobic surfaces created by surfactant adsorption to mica surfaces

Hydrophobic surfaces created by the adsorption of a monolayer of surfactants, such as CTAB or DODAB, to mica display long-range mutual attraction when placed in water. Initially, this attraction was considered to be due to hydrophobic interaction, but more careful measurements using AFM showed that the surfactant monolayer undergoes rearrangements to produce charged patches on the surface; therefore, the nature of the long-range interaction is due to the electrostatic interaction between patches. The monolayer rearrangement depends on the nature of the surfactant and its counterion. To study possible monolayer rearrangements in molecular detail, we performed detailed molecular dynamics computer simulations on systems containing a monolayer of surfactants RN(CH(3))(3)(+)Cl(-) (R indicates a saturated hydrocarbon chain) adsorbed on a mica surface and immersed in water. We observe that when chain R is 18 carbons long the monolayer rearranges into a micelle but it remains a monolayer when the chain contains 24 carbons.     

Interactions of quaternary ammonium salt-type gemini surfactants with sodium poly(styrene sulfonate)

The interactions of cationic gemini surfactants, 1,2-bis(alkyldimethylammonio)ethane dibromide (m-2-m: m is hydrocarbon chain length, m = 10 and 12), and an anionic polymer, sodium poly(styrene sulfonate) (PSS), have been characterized by several techniques such as tensiometry, fluorescence spectroscopy, and dynamic light scattering. The surface tension of gemini surfactant/PSS mixed systems decreases with surfactant concentration, reaching break points, which are taken as critical aggregation concentrations (cac). The surface tension at the cac of mixtures is higher than that of single surfactants, and it is found that at concentrations above the cac, the surfactant molecules are associated with the polymer in the bulk. The 12-2-12/PSS mixed system shows higher surface activity than both 10-2-10/PSS and the monomeric surfactant of dodecyltrimethylammonium bromide/PSS systems. Fluorescence measurements of these mixed systems suggest the formation of a complex with a highly hydrophobic environment in the bulk of the solution. Additionally, dynamic light scattering measurements show that the hydrodynamic diameter of the 12-2-12/PSS mixed system is smaller than that of PSS only at low concentration, indicating interactions between surfactant and polymer. These result from the electrostatic attraction between ammonium and sulfate headgroups as well as the hydrophobic interaction between their hydrocarbon chains.     

Polymeric alkenoxy amino acid surfactants: IV. effects of hydrophobic chain length and degree of polymerization of molecular micelles on chiral separation of beta-blockers

Four alkenoxy leucine-based surfactants with C8-C11 chains containing a terminal double bond, and one C11 chain surfactant with a terminal triple bond are synthesized and characterized in monomeric and polymeric forms. These polymeric pseudophases are then utilized to study the influence of chain length and DP for the enantioseparations of seven beta-blockers in MEKC. Variations in chain length and concentration of polymeric surfactants showed significant effects on the chiral resolution (Rs) and efficiency (N). A relatively large elution range combined with the highest polarity and aggregation number (A) but the lowest retention time, partial specific volume, and optical rotation generated with C8-polymeric surfactant results in simultaneous enantioseparation of all seven beta-blockers with higher N and R(s). In particular, highly hydrophobic beta-blockers are better resolved with shorter hydrocarbon chain even at higher surfactant concentration, which is unachievable with longer chain surfactant. On the other hand, polymer derived from C11-triple bond provided smaller A value compared to C11-double bond surfactant. However, chiral Rs of hydrophobic beta-blockers are still achievable with the C11-triple bond surfactant with enhanced N and shorter analysis time. In addition, effect of polymerization concentration is evaluated by polymerizing all five surfactants at five times their respective CMCs and 100 mM equivalent monomer concentrations. Polymerization of shorter chain (C8 and C9) double-bonded surfactants at five times their respective CMCs results in higher A values with better chiral Rs and N compared to the same two surfactants polymerized at 100 mM.