四乙铵离子对阴离子表面活性剂及其混合体系的表面活性和胶团形成的影响

研究了溴化四乙铵介质中十二烷基硫酸四乙铵、全氟辛基磺酸四乙铵及其混合体系的表面化学性质。四乙铵离子在浓度较小时主要起电解质反离子作用,在浓度较大时则明显参与表面吸附和胶团的形成,其作用相当于在表面活性离子的疏水链上“引入”碳氢链,从而导致表面活性提高和碳氢/碳氟表面活性剂混合体系中碳氢/碳氟链间的互疏作用减弱等。     

Derivation and synthesis of renewable surfactants

This critical review focuses on the origins and preparation of bio-based surfactants, defined here as non-soap, amphiphilic molecules in which the carbon atoms are derived from annually renewable feedstocks. Environmental concerns and market pressures have led to greater relevance of these chemicals in commercial applications in recent years and extensive research has gone into exploring new classes of surfactants. Highlighted here are examples of bio-based surfactants that are produced on an industrial scale and/or are based on abundant starting materials. The trend of increasing use of renewable resources as starting materials for surfactants is introduced, followed by extensive discussion of the major classes of bio-derived hydrophobes and hydrophiles. Also discussed is the status of research and development with regard to biosynthetically produced surfactants. Finally, concluding remarks address the potential for new surfactant molecular structures as a result of ongoing development in the chemistry of biorefineries, i.e., that the transformation of lignocellulose into fuels is likely to support the manufacturing of new bio-based coproducts (238 references).     

Study of Cryostructuring of Polymer Systems: 25. The Influence of Surfactants on the Properties and Structure of Gas-Filled (Foamed) Poly(vinyl alcohol) Cryogels

Foamed poly(vinyl alcohol) (PVA) cryogels are studied. Such heterogeneous gel composites are formed as a result of the cryogenic treatment (freezing—storage in a frozen state—thawing) of water— PVA liquid foams in the absence and presence of surfactants. It is shown that the addition of ionic and nonionic surfactants to an aqueous PVA solution and its subsequent foaming result in the formation of liquid foam whose stability is lower than that of the foam prepared from an aqueous PVA solution in the absence of surfactant, i.e., surfactants cause a destabilizing effect on the foams containing PVA. Gas-filled PVA cryogels formed as a result of freezing—thawing of such foams contain large (up to ～180 μm) pores (air bubbles incorporated into the matrix of heterogeneous gel). Mechanical and thermal properties of cryogels depend on the nature and concentration of surfactants, as well as on the regime of cryogenic treatment. The rigidity of foamed PVA cryogels prepared in the presence of sodium dodecyl sulfate and cetyltrimethylammonium bromide ionic surfactants is lower and that in the presence of nonionic decaoxyethylene cetyl ether is higher than for equiconcentrated (by the polymer) foamed PVA cryogel containing no surfactant. Microscopic studies and the analysis of obtained images of cryogel structure demonstrate that the effect of surfactant on the morphology of freezing foam can be different, depending on the type of surfactant added to the initial system. This leads to foam-destabilizing effects such as the collapse, deformation, and coalescence of air bubbles; the failure of gel phase structure near the bubble surface; etc. However, the complete disintegration of the foamed structure is prevented by a very high viscosity of the unfrozen liquid microphase of a macroscopically solid sample and by the cryotropic PVA gelation that fixes the structure of partially destroyed foam.     

Enhanced fluorescence of triphenylmethane dyes in aqueous surfactant solutions at supramicellar concentrations--effect of added electrolyte

The colour change of triphenylmethane (TPM) dyes induced by surfactants at concentrations much greater than their critical micellar concentrations is found to be accompanied by enhanced fluorescence. Thus, the otherwise weak fluorescence of TPM dyes can be detected using supramicellar surfactant concentrations. In this respect, the nonionic polyoxyethylene (POE) chain-containing surfactants are found to be more efficient compared with ionic surfactants. The POE surfactants, Triton X-100, Tween-20 and Tween-60 present a polymer-like surface to the dyes, which can thus easily bind to them. At supramicellar concentrations, the hydrophobic environment formed in these micelles is effective in preventing nonradiative relaxation processes of the dyes. As a result, there is enhanced fluorescence for even micromolar concentrations of the dyes. Among the Tween series, Tween-60 being more hydrophobic leads to greater fluorescence enhancement than Tween-20. From the fluorescence properties, binding constants for dye binding to the surfactants can be determined. Thus the relative efficiency of these surfactants as binding substrates can be assessed. Another interesting observation is that the electrolyte LiCl in presence of the surfactants leads to even larger fluorescence enhancement than the surfactants alone.     

Geometrical shape of micelles formed by cationic dimeric surfactants determined with small-angle neutron scattering

The influence of spacer group on the geometrical shape of micelles formed by quaternary-bis dimeric (Gemini) surfactants C(12)H(25)N(CH(3))(2)(CH(2))(s)N(CH(3))(2)C(12)H(25) (12-s-12) has been investigated with small-angle neutron scattering (SANS). Dimeric surfactants with a short spacer unit (12-3-12 and 12-4-12) are observed to form elongated general ellipsoidal micelles with half axes a < b < c, whereas SANS data demonstrate that 12-s-12 surfactants with 6 ≤ s ≤ 12 form rather small spheroidal micelles rather than strictly spherical micelles. By means of comparing our present SANS results with previously determined growth rates using time-resolved fluorescence quenching, we are able to conclude that micelles formed by 12-6-12, 12-8-12, 12-10-12, and 12-12-12 are shaped as oblate rather than prolate spheroids. As a result, our present investigation suggests a never before reported structural behavior of Gemini surfactant micelles, according to which micelles transform from elongated ellipsoids to nonelongated oblate spheroids as the length of the spacer group is increased. The aggregation number of oblate micelles is observed to monotonously decrease with an increasing length of the surfactant spacer group, mainly as a result of a decreasing minor half axis (a), whereas the major half axis (b) is rather constant with respect to s. We argue that geometrically heterogeneous elongated micelles are formed by dimeric surfactants with a short spacer group mainly as a result of the surface charges becoming less uniformly distributed over the micelle interface. As the length of the spacer group increases, the distance between intramolecular charges become approximately equal to the average distance between charges on the micelle interface, and as a result, rather small oblate spheroidal micelles with a more uniform distribution of surface charges are formed by dimeric 12-s-12 surfactants with 6 ≤ s ≤ 12.     

Assembly of a model hydrophobic drug into cationic bilayer fragments

Catanionic surfactants result from the pairing of oppositely charged amphiphilic molecules, forming a new class of surfactant molecules with various interesting lyotropic and thermotropic properties. With the aim of probing the role of both headgroup chemical nature/structure and molecular shape, a series of catanionic surfactants were synthesized. The cationic portion of the molecule is kept constant, being the dioctadecyldimethylammonium double chain. Different single-chained surfactants with varying headgroups and chain lengths are used as the anionic pair. The thermotropic behavior has been studied by DSC and the mesophase structural investigated by polarized light microscopy. The results indicate that, for a given chain length, parameters such as headgroup polarity and charge density, as well as volume, influence the catanionic surfactant behavior. The thermodynamic parameters are qualitatively evaluated, considering the headgroup chemical nature and the overall molecular structure.     

Aggregation and reactivity in aqueous solutions of cationic surfactants and aromatic anions across concentration scales

The use of aqueous solutions as solvents in synthetic chemistry is one of the pathways towards more sustainable chemical processes. To increase solubility of reactants in aqueous solutions, surfactants can be used. In particular as a result of detailed kinetic studies involving probe reactions, our current understanding of the reaction environment offered by micelles is good to excellent. However, this understanding does not always translate well to reactions on a synthetic scale because concentrations are typically very different from concentrations used in probe reactions. These high concentrations may lead to changes in aggregate morphologies, in particular where aromatic anions are used in combination with cationic surfactants. An overview of aggregation processes and aggregate morphologies across concentration scales is presented together with a discussion of the resulting effects on reactivity in solutions containing cationic surfactants and (reactive) aromatic anions.     

Organization of amphiphiles: XII. Evidence in favor of formation of hydrophobic complexes in aqueous solution

The effects of nonionic surfactants OP-10 and OP-30 (polyoxyethylated octyl phenols with 10 and 30 oxyethylene groups, respectively) in surfactant mixtures with ionic surfactants hexadecyltrimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) have been investigated by a conductometric method in conjunction with fluorescence, surface tension, zeta potential, and DLS measurements. The interactions are found to be antagonistic in nature for each of the systems; i.e., micellization of CTAB as well as SDS is hindered on addition of the nonionic surfactants. The antagonism is found to be more prominent in the presence of OP-10 compared to that of OP-30. Two types of mechanistic paths, path A operating below the critical micellar concentration and path B operating beyond the critical micellar concentration of nonionic surfactants, have been suggested. In path A, the retardation in micellization has been attributed to a decrease in monomeric concentration of the ionic surfactants from solution as a result of the formation of a hydrophobic complex between nonionic and ionic surfactants. In path B, the decrease in monomer concentration is due to the solubilization of the ionic surfactant in micelles of the nonionic surfactants in a 1:1 stoichiometric ratio. A theoretical treatment to the interaction in each ionic-nonionic pair yields a positive value of the interaction parameter supporting the concept of antagonism. The formation of the hydrophobic complex is supported by fluorescence and surface tension measurements. A schematic representation of the stabilization of these hydrophobic complexes has been suggested. The association of ionic surfactants by nonionic micelles is suggested by zeta potential and DLS studies.     

Effects of added surfactants on thermoreversible gelation of associating polymer solutions

The influence of added surfactants on physical properties of associating polymer solutions was examined by a new statistical‐mechanical theory of associating polymer solutions with multiple junctions and by computer simulation. The sol–gel transition line, the spinodal line, and the number of elastically effective chains in the mixed networks were calculated as functions of the concentration of added surfactants. All of them exhibited nonmonotonic behavior as a result of the following two competing mechanisms. One was the formation of new mixed micelles by binding surfactants onto the polymer associative groups. These micelles serve as crosslink junctions and promote gelation. The other was the replacement of polymer associative groups in the already formed network junctions by added surfactants. Such replacement lowers connectivity of junctions and destroys networks. The critical micelle concentration was also calculated. The results are compared with the reported experimental data on poly(ethylene oxide)‐based associating polymers and hydrophobically modified cellulose derivatives. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 733–751, 2004     

BRCMINATED,CHLORINATED AND HYDROXYLATED SURFACTANTS DERIVED FROM OLEYL CHAIN - PART II EMULSIFYING PROPERTIES

Bromination, chlorination and hydroxylation were carried out on the hydrophobic chain of several comnercially available nonionic surfactants in order to modify their hydrophobic characteristics without changing their hydrophilic moities. Ethoxy-lated oleyl alcohols, as well as ethoxylated oleic acid, and polyglycerol esters were examined and it was found that paraffinic oil-in-water emulsions can be stabilized using these new surfactants. The derivatization of the nonionic surfactants increased their overall hydrophilicity, and as a result higher HLB value was obtained for any of the surfactants. It should be noted that in spite of the fact that hydrophilic groups were introduced into the hydrocarbon chain, stable emulsions were prepared and in sane cases even better stabilities were observed.     

羧甲基纤维素系列高分子表面活性剂的嵌段结构对其形态和性能的影响

采用超声波辐照聚合的羧甲基纤维素 (CMC)系列高分子表面活性剂是由CMC嵌段和含有等长双亲性支链的嵌段构成的共聚物 ,研究结果表明 ,CMC链段保证了共聚物的增粘性能 ,双亲性嵌段提供了共聚物优良的表面活性 ;CMC增粘嵌段与表面活性嵌段作为共聚物的两个嵌段 ,各发挥其作用 ,得到既有增粘性能又有高表面活性的双亲性共聚物 .     

Magneto-Adaptive Surfactants Showing Anti-Curie Behavior and Tunable Surface Tension as Porogens for Mesoporous Particles with 12-Fold Symmetry

Gaining external control over self-organization is of vital importance for future smart materials. Surfactants are extremely valuable for the synthesis of diverse nanomaterials. Their self-assembly is dictated by microphase separation, the hydrophobic effect, and head-group repulsion. It is desirable to supplement surfactants with an added mode of long-range and directional interaction. Magnetic forces are ideal, as they are not shielded in water. We report on surfactants with heads containing tightly bound transition-metal centers. The magnetic moment of the head was varied systematically while keeping shape and charge constant. Changes in the magnetic moment of the head led to notable differences in surface tension, aggregate size, and contact angle, which could also be altered by an external magnetic field. The most astonishing result was that the use of magnetic surfactants as structure-directing agents enabled the formation of porous solids with 12-fold rotational symmetry.     

BRCMINATED,CHLORINATED AND HYDROXYLATED SURFACTANTS DERIVED FROM OLEYL CHAIN - PART II EMULSIFYING PROPERTIES

ABSTRACT

Bromination, chlorination and hydroxylation were carried out on the hydrophobic chain of several commercially available nonionic surfactants in order to modify their hydrophobic characteristics without changing their hydrqphilic iroities- Ethoxy-lated oleyl alcohols, as well as ethoxylated oleic acid, and polyglycerol esters were examined and it was found that paraf-finic oil in water emulsions can be stabilized using these new surfactants. The derivatization of the nonionic surfactants increased their overall hydrophilicity and as a result higher HLB value was obtained for any of the surfactants.It should be noted that inspite the fact that hydrqphilic groups were introduced into the hydrocarbonic chain, stable emulsions were prepared and in some cases even better stabilities were measured.     

Bending elasticity of charged surfactant layers: the effect of mixing

Expressions have been derived from which the spontaneous curvature (H(0)), bending rigidity (k(c)), and saddle-splay constant (k(c)) of mixed monolayers and bilayers may be calculated from molecular and solution properties as well as experimentally available quantities such as the macroscopic hydrophobic-hydrophilic interfacial tension. Three different cases of binary surfactant mixtures have been treated in detail: (i) mixtures of an ionic and a nonionic surfactant, (ii) mixtures of two oppositely charged surfactants, and (iii) mixtures of two ionic surfactants with identical headgroups but different tail volumes. It is demonstrated that k(c)H(0), k(c), and k(c) for mixtures of surfactants with flexible tails may be subdivided into one contribution that is due to bending properties of an infinitely thin surface as calculated from the Poisson-Boltzmann mean field theory and one contribution appearing as a result of the surfactant film having a finite thickness with the surface of charge located somewhat outside the hydrophobic-hydrophilic interface. As a matter of fact, the picture becomes completely different as finite layer thickness effects are taken into account, and as a result, the spontaneous curvature is extensively lowered whereas the bending rigidity is raised. Furthermore, an additional contribution to k(c) is present for surfactant mixtures but is absent for k(c)H(0) and k(c). This contribution appears as a consequence of the minimization of the free energy with respect to the composition of a surfactant layer that is open in the thermodynamic sense and must always be negative (i.e., k(c) is generally found to be brought down by the process of mixing two or more surfactants). The magnitude of the reduction of k(c) increases with increasing asymmetry between two surfactants with respect to headgroup charge number and tail volume. As a consequence, the bending rigidity assumes the lowest values for layers formed in mixtures of two oppositely charged surfactants, and k(c) is further reduced in anionic/cationic surfactant mixtures where the surfactant in excess has the smaller tail volume. Likewise, the reduction of k(c) is enhanced in mixtures of an ionic and a nonionic surfactant where the ionic surfactant has the smaller tail. The effective bilayer bending constant (k(bi)) is also found to be reduced by mixing, and as a result, k(bi) is seen to go through a minimum at some intermediate composition. The reduction of k(bi) is expected to be most pronounced in mixtures of two oppositely charged surfactants where the surfactant in excess has the smaller tail in agreement with experimental observations.     

Formation of vesicles with an organometallic amphiphile bilayer by supramolecular arrangement of metal carbonyl metallosurfactants

Metallo-vesicles are formed in water medium as a result of the supramolecular arrangement of molybdenum carbonyl metallosurfactants. These new kind of surfactants contain a hydrophobic metal carbonyl fragment and are easily prepared from surfactant phosphine ligands.     

The role of surface viscoelasticity in slide coating processes

In the slide hopper coating process for simultaneously applying multiple layers of coating liquids to a moving web, surfactants must be added to the photographic emulsion to ensure a stable position of the liquid bridge formed between the lower edge of the slide hopper and the moving web. In slide coating of gelatin solutions without an added surfactant, the liquid bridge becomes instable and begins to oscillate if critical coating conditions are reached. The addition of anionic surfactants stabilizes the liquid bridge against oscillations. The action of the added surfactants is a result of their interaction with gelatin. The degree of binding can be used as a measure of the interaction. The binding of anionic and cationic surfactants to gelatin was investigated using a surfactant-selective electrode. The binding isotherms of the surfactants to an alkali-processed bone gelatin were determined and compared with the surface dilational properties of the gelatin/surfactant adsorption layers. The comparison of surface rheological data obtained by the oscillating bubble method with the results of coating experiments demonstrates that the viscoelastic properties of gelatin/anionic surfactant adsorption layers are of essential importance to the stabilization of the liquid bridge against oscillations. Pure elastic adsorption layers are not able to stabilize the liquid bridge. The mechanism of the stabilizing action is discussed. Received: 30 October 2000/Revised: 12 February 2001/Accepted: 14 February 2001     

Surfactants Used in Food Industry: A Review

The understanding of the formation, structures, and properties of emulsions is essential to the creation and stabilization of structures in food. The increasing use of surfactants, the identification of compounds with low toxicity and good surface activity properties is of great interest. The relevance of the major end points specified in the Organisation for Economic Co-operation and Development (OECD) guidelines for the hazard assessment of food chemicals is critically analyzed and main parameters are acute toxicity, subacute repeated studies, allergy, reproductive toxicity, long-term studies, and mutagenicity tests. We focus this article on surfactant association structures and food colloids. There is almost infinite number of combinations are organized and arranged in very complex internal microstructures with various types of assemblies such as dispersions, emulsions, foams, gels, etc. Low-mass surfactants are very mobile at the interface and they are particularly efficient reducing the interfacial tension. As a result, they rapidly coat the freshly created oil-water interface during emulsification. In this category, we mainly mentioned monoglycerides, lecithins, glycolipids, fatty alcohols and fatty acids. High-mass surfactants cover protein and polysacharide groups. The protein molecule may interpenetrate in the lipid phase to various degrees. The specific binding is predominantly electrostatic: The headgroups of the surfactants bind to groups of opposite charge on the protein. The saturation binding for anionic surfactants is pH-independent and seems to be controlled by the cooperative hydrophobic interactions. Polysaccharides and smallmolecule surfactants are two of the predominant groups of amphiphilic materials that have been explored for the stabilization of emulsions. One of the most important aspects of polymer-surfactant systems is their ability to control stability and rheology over a wide range of composition. Biocompatible, biodegradable, and/or nontoxic emulsion-based formulations have great potential for applications in the food. The combination of particular characteristics such as emulsifying, anti-adhesive and antimicrobial activities presented by biosurfactants suggests potential application as multipurpose ingredients or additives.     

Magneto‐Adaptive Surfactants Showing Anti‐Curie Behavior and Tunable Surface Tension as Porogens for Mesoporous Particles with 12‐Fold Symmetry

Gaining external control over self‐organization is of vital importance for future smart materials. Surfactants are extremely valuable for the synthesis of diverse nanomaterials. Their self‐assembly is dictated by microphase separation, the hydrophobic effect, and head‐group repulsion. It is desirable to supplement surfactants with an added mode of long‐range and directional interaction. Magnetic forces are ideal, as they are not shielded in water. We report on surfactants with heads containing tightly bound transition‐metal centers. The magnetic moment of the head was varied systematically while keeping shape and charge constant. Changes in the magnetic moment of the head led to notable differences in surface tension, aggregate size, and contact angle, which could also be altered by an external magnetic field. The most astonishing result was that the use of magnetic surfactants as structure‐directing agents enabled the formation of porous solids with 12‐fold rotational symmetry.     

Influence of surfactants on laser-induced copper deposition from solution

The influence of surfactants on the result of laser induced copper deposition from solution on the dielectric surface was studied. The dependences of the topology of the copper structures on the hydrophilic—lipophilic balance of non-ionogenic surfactants was found. The surface tension at the gas phase—solution interface was measured. The best results of laser deposition are obtained by the use of non-ionogenic surfactants with low values of hydrophilic—lipophilic balance.     

Stability and Adsorption Properties of Suspensions of Finely Dispersed Silica in the Presence of Cationic Surfactants

Interrelation between the coagulation rate, adsorption and electrokinetic properties of silica polydisperse suspensions in the presence of cationic surfactants is studied. The highest coagulation rate is observed in a certain concentration range of the cationic surfactants. When pH values increases, an increasing amount of cationic surfactant is required to achieve maximal coagulation rate. For bisquaternary cationic surfactants, ethonium and decamethoxine, maximal coagulation rate is observed at concentrations by an order of magnitude lower than for monoquaternary cetyltrimethylammonium bromide. It is concluded that the suspensions lost their stability as a result of both neutralization of particle surface charge and flocculating effect of the cationic surfactants. Moreover, the flocculation mechanism depends on the cationic surfactant nature and physicochemical parameters of the medium, ionic strength and pH.