Skin Constituents as Cosmetic Ingredients. Part I: A Study of Bio‐mimetic Monoglycerides Behavior at the Squalene‐Water Interface by the “Pendant Drop” Method in a Static Mode

This work presents the behavior of bio‐mimetic monoglycerides at the squalene/water interface. The study was done in the so‐called “static” mode using the “pendant drop method”, enabling us to characterize these molecules according to the value of their critical efficiency concentration (CEC), their maximum surface excess concentration (Γ_∞), the efficiency of the surface tension reduction parameter (pC20), and the minimum value of their interfacial tension (γ_min). It also permitted the study of the influence of the structure of the carbon chain of those monoglycerides on their interfacial behavior.

The analysis of the different parameters shows that monoglycerides with small hydrocarbon chains, monoglycerides with one or more double bonds, and monoglycerides possessing a hydroxyl function grafted in the middle of the chain constitute excellent surfactants. Two different groups can be found: one group composed of short saturated hydrocarbon chain monoglycerides (C12∶0 to C16∶0) and long hydrocarbon chain monoglycerides (C18∶0 to C22∶0); the second group, composed of unsaturated hydrocarbon chain monoglycerides, also includes hydroxystearate and isostearate monoglycerides. The first group could be used for the formulation of “hydrating” cosmetic products having secondary droplets, the second group for W/O emulsions.     

Competitive adsorption of surfactants and hydrophilic silica particles at the oil-water interface: interfacial tension and contact angle studies

The effect of surfactants' type and concentration on the interfacial tension and contact angle in the presence of hydrophilic silica particles was investigated. Silica particles have been shown to have an antagonistic effect on interfacial tension and contact angle in the presence of both W/O and O/W surfactants. Silica particles, combined with W/O surfactant, have no effect on interfacial tension, which is only dictated by the surfactant concentration, while they strongly affect interfacial tension when combined with O/W surfactants. At low O/W surfactant, both particles and surfactant are adsorbed at the interface, modifying the interface structure. At higher concentration, interfacial tension is only dictated by the surfactant. By increasing the surfactant concentration, the contact angle that a drop of aqueous phase assumes on a glass substrate placed in oil media decreases or increases depending on whether the surfactant is of W/O or O/W type, respectively. This is due to the modification of the wettability of the glass by the oil or water induced by the surfactants. Regardless of the surfactant's type, the contact angle profile was dictated by both particles and surfactant at low surfactant concentration, whereas it is dictated by the surfactant only at high concentration.     

Interfacial self-organization of bolaamphiphiles bearing mesogenic groups: relationships between the molecular structures and their self-organized morphologies

This article discusses the relationship between the molecular structure of bolaamphiphiles bearing mesogenic groups and their interfacial self-organized morphology. On the basis of the molecular structures of bolaamphiphiles, we designed and synthesized a series of molecules with different hydrophobic alkyl chain lengths, hydrophilic headgroups, mesogenic groups, and connectors between the alkyl chains and the mesogenic group. Through investigating their interfacial self-organization behavior, some experiential rules are summarized: (1) An appropriate alkyl chain length is necessary to form stable surface micelles; (2) different categories of headgroups have a great effect on the interfacial self-organized morphology; (3) different types of mesogenic groups have little effect on the structure of the interfacial assembly when it is changed from biphenyl to azobenzene or stilbene; (4) the orientation of the ester linker between the mesogenic group and alkyl chain can greatly influence the interfacial self-organization behavior. It is anticipated that this line of research may be helpful for the molecular engineering of bolaamphiphiles to form tailor-made morphologies.     

神木煤显微组份的表面特性

煤表面亲水性是影响水煤浆(CWS)流变性能的重要因素。关于表面活性剂和煤岩组成对煤亲水性影响的研究比较少,本文在这方面进行了一些工作,旨在弄清神木煤配CWS的制约因素。1.实验部分煤样采自神府煤田神木区四门沟矿3~(-1)层。用手选法选出镜煤和丝炭,经破碎、筛分制成80—180目研究样品。     

Promotion of organic reactions by interfacial hydrogen bonds on hydroxyl group rich nano-solids

Surface hydroxyl group rich nano-structured solids dramatically increase the rate of several organic reactions; such effect is attributed to the formation of interfacial hydrogen bonds between the surface hydroxyl groups and the reactants; this catalytic effect is versatile and applicable for a broad range of reaction conditions.     

Studies of Interfacial Activities of Four Kinds of Surfactants at Oil/Water Interface

This article aims to compare the interfacial activities of different kinds of surfactants in the same oil/water system. The anionic surfactants of alkylbenzene sulfonates, the polyoxyethylenated nonionic surfactants, the cationic surfactants of alkyl trimethyl ammonium chlorides, and the zwitterionic surfactants of alkyl hydroxyl sulfobetaines were used, and the interfacial tensions of the surfactant solutions against kerosene at different NaCl concentrations were measured. It is found that the interfacial activities of the alkylbenzene sulfonates are high and ultralow interfacial tensions (<0.01 mN/m) can be obtained at proper salinities. While, the nonionic surfactants have relatively low interfacial activities and the minimum tensions are around 0.01 mN/ms. The salinity scanning curves of the alkylbenzene sulfonates and nonionic surfactants decrease first, then increase, showing their interfacial activities can be changed by the salinity effectively. The cationic and zwitterionic surfactants have very low interfacial activities, of which all the tensions are higher than 0.1 mN/ms and are hard to be changed by the salinity. The experimental results may have important reference values for enhanced oil recovery.     

The structure of modifying layers and identification of residual hydrophilic groups on modified silica surface by the adsorption and chromatographic measurements

Amorphous silica Silochrom-80 is modified in a liquid phase in two stages with poly(ethylhydrosiloxane) and hexamethyldisilazane. Adsorption studies suggest that the modified silicas have a porous structure. Hexamethyldisilazane is found to have an active role in the modification of the secondary porous structure of the samples. The thickness of modifying layers on the surface of the samples is calculated. Residual hydrophilic sites are identified on the modified silica surface, and their concentration is determined using chromatography data and the parameters of the Langmuir equation. It is shown that the two-stage modification of silica with the selected reagents makes it possible to entirely deactivate the most active vicinal hydroxyl groups on the sorbent surface and, to a substantial extent, its isolated hydroxyl groups.     

Critical Phenomena in the Clouding Behavior of Nonionic Surfactants Induced by Additives

Effects of anionic surfactants, hydrotropes, and electrolytes on the cloud point of Triton X-100 have been studied over six decades of additives concentrations. A comprehensive look at all the data reveals significant new learnings. While anionic surfactants and hydrotropes affect the cloud point of non-ionics at ultra low (monomeric) concentrations, electrolytes exhibit a minimum critical concentration above which they cast their effect. This suggests that the former work by modifying the surface charge of non-ionic micelles (i.e., by affecting the solute), whereas the latter work by modifying the properties of the bulk medium. Above their respective critical concentrations, salting-out electrolytes decrease the cloud point while salting-in electrolytes increase it, the trends being linear with additive concentration in either case. The magnitude of the effect of anionic surfactants and hydrotropes increases gradually with increasing concentration till their respective cmc's are reached and then there is a sharp rise in the cloud point. Copyright 1999 Academic Press.     

Ultra-Low Interfacial Tension Between Heavy Oil and Betaine-Type Amphoteric Surfactants

Betaine surfactants with lipophilic groups of different lengths were synthesized in this research and the dynamic interfacial tension (IFT) between solutions of these surfactants and three kinds of crude oil from Shengli Oilfield are measured. The results indicated that, for Gudao and Gudong heavy oil, cetyl dimethyl hydroxyl sulfobetaine (SBET-16) was the most efficient in lowering the IFT in the case of no alkalis, while for Shengtuo heavy oil, cetyl dimethyl carboxymethyl betaine (CBET-16) was best. SBET-16 with the concentration of 0.003–0.1% and 0.005–0.1% can reduce the oil/water IFT to ultra-low for Gudao and Gudong oil respectively, CBET-16 with the concentration of 0.005–0.1% can lower the oil/water IFT to ultra-low for Shengtuo oil. These results showed that for different oils, an oil displacement agent with high capacity to lower the oil/water interfacial tension may be obtained only by changing the molecular structure of betaine surfactant. This study can be used to guide the design of surfactants for alkaline-free combination flooding.     

Synthesis and surface active properties of a gemini-type surfactant linked by a quaternary ammonium group

In this study, cationic surfactants having multi-hydroxyl groups were synthesized by the condensation reaction of octadec-9-enyl glycidyl ether and methyl amine followed by the quaternization with dimethyl sulfate. The structure of the product was elucidated by ¹H-NMR and FT-IR. The minimum critical micelle concentration (CMC) and surface tension achieved using C18:1-BHDM surfactant were 1.24?×?10^?4?mol/L and 43.36 mN/m, respectively. The interfacial tensions measured between 1 wt% surfactant solution and n-decane were found to be in the same order of magnitude as those exhibited between micellar solutions and nonpolar hydrocarbon oils. The contact angle measurement result suggests that C18:1-BADM is the best wetting agent among the surfactants tested during this study. It has been observed that the results for foam stability measurement are consistent with those of CMC and contact angle. That is, the percentage of foam volume decrease has been observed to increase with an increase in number of hydroxyl group.     

Geometric constraints at the surfactant headgroup: effect on lipase activity in cationic reverse micelles

The primary objective of the present article is to understand how the geometric constraints at the surfactant head affect the lipase activity in the reverse micellar interface. To resolve this issue, surfactants were designed and synthesized, and activity was measured in /water/isooctane/n-hexanol reverse micellar systems at z ([alcohol]/[surfactant])=5.6, pH 6.0 (20 mM phosphate), 25 degrees C across a varying range of W0 ([water]/[surfactant]) using p-nitrophenylalkanoates as the substrate. It was observed that lipase activity increases from surfactants to with the increment in surface area per molecule (Amin) because of the substitution by the bulky tert-butyl group at the polar head. However, the activity was found to be similar for despite an enhancement in the hydrophilic moieties at the interface. This unchanged lipase activity is presumably due to the comparable surface area of to originating from the rigidity at the surfactant head. Noticeably, the enzyme activity improved from with the simultaneous increment of both the hydroxyl group and the flexibility of the headgroup whereas that for increased exclusively with the flexibility of the headgroup. The common parameter in both groups of surfactants and is the flexibility of the headgroup, which possibly enhance Amin and consequently the lipase activity. Thus, the geometric constraints at the surfactant headgroup play a crucial role in modulating the lipase activity profile probably because of the variation in interfacial area.     

双子表面活性剂及其抗菌性能

Gemini surfactants contain two hydrophilic and two hydrophobic groups connected by a linkage close to the hydrophilic groups. Gemini surfactants have lower critical micelle concentration, higher surface activity, greater efficiency in decreasing the surface tension of water and the interfacial tension between water and oil, and better water solubility than conventional surfactants. Gemini surfactants are widely used as sterilizing, bacteriostatic, anti-foaming, and drug release agents in various enterprises including food production and industrial cleaning. They, therefore, play a very important social, economic, and industrial role. This paper briefly summarizes gemini surfactant development, structure, self-assembly, activity, classification, and characteristics, as well as focuses on the antibacterial mechanisms of these compounds. It is expected that the antibacterial properties of gemini surfactants may help slow the spread of the novel coronavirus (2019-nCoV).     

The role of the surfactant head group in the emulsification process: Single surfactant systems

To clarify the effect of the surfactant head group on the emulsification process, dilute dodecane in water emulsions were prepared in a small flow-through cell with three surfactants which had the same hydrocarbon tail length but different head groups. The different surfactants types were (a) a nonionic, hexa(ethyleneglycol) mono n-dodecyl ether (C12E6), (b) an anionic, sodium dodecyl sulfate (SDS), and (c) a cationic, n-dodecyl pyridinium chloride (DPC), and the emulsions were prepared under the same conditions. From dynamic light scattering measurements, it was shown that the mean steady state droplet size of the emulsions (obtained after 20 min dispersion) could be related to the interfacial tension at concentrations in the region of the cmc. This result was in agreement with laminar and turbulent viscous flow theory. However, the particle size versus surface tension data for the different surfactant systems did not fall on a single line. This behavior suggested that the surfactant played a secondary role in defining the droplet size (in addition to reducing the interfacial tension) possibly through diffusion and relaxation, during deformation of the interface. In addition, it was found that the values of the equilibrium "surfactant packing densities" of the different surfactants at the oil/water interface were almost equal near the cmc, but the mean droplet size and the interfacial tension at the cmc decreased following the order DPC>SDS>C12E6 .     

Microcalorimetric Study of Methanol Adsorption on Initial Silica and Silica Modified with Polyfluoroalkyl Groups

The adsorption of methanol on initial silica and modified silica samples containing large mesopores is studied by the adsorption–calorimetric method. The grafted tridecylfluoroalkyl groups have a tilted orientation on the silica and physically screen the part of the surface OH groups that have not been involved in the reaction with a modifier. Adsorbed methanol makes the modifying layer looser, thus facilitating the accessibility of methanol molecules to these hydrophilic adsorption sites. Concentrations of OH groups involved in the chemical interaction with molecules of the modifier, OH groups physically screened by its organofluoric radicals, and OH groups located on the surface areas free of the modifier are quantitatively estimated. An additional silanization of the modified silica leads to coverage of silica surface areas that are free of organofluoric modifier with trimethylsilyl radicals. The heat of interaction between the methanol molecules and silica surface hydroxyl groups is determined; it is equal to 60 kJ/mol. The structure of the modifying organofluoric layer and changes in this structure that resulted from additional silanization of the surface and from the methanol adsorption are discussed.     

Interfacial activity of a novel family of polymeric surfactants

A novel series of polymeric surfactants based on carboxy methyl cellulose and alkyl poly(etheroxy) acrylate were synthesized by ultrasonic irradiation. These polymeric surfactants have exhibit excellent surface activity due to their unique structure. The influences of salt, alcohol and alkali on the interfacial activity of these polymeric surfactants were studied by interfacial tensiometery, dynamic laser scattering (DLS), UV spectroscope and environmental scanning electrical microscope (ESEM). The surface tension and interfacial tension (IFT) properties change little with NaCl added. The formed micelles shrink, their size becomes smaller. Alcohols cause the IFT to decrease a little because a small amount of free chains present in solution. Under the influence of added alkali, the IFT of the polymeric surfactants, in aqueous solution, decreases so much that sometimes it is less than 10⁻² mN/m. Using data from the equivalent alkane scan, one cannot draw the conclusion that the action of alkali with the acidic components in crude oil leads to the ultra-low IFT. The analyses by UV, DLS and ESEM show that the micelles formed by polymeric surfactants could be disaggregated or destroyed sharply by the action of alkali. So the size of micelles decreases greatly and the number of free chains increases. That more polymeric surfactants molecules move to the interface of oil/water and rearrange at the interface of oil/water is believed to be the main reason of the ultra-low IFT (10⁻³ mN/m) that is obtained.     

Interfacial activity of polymer-coated gold nanoparticles

A systematic study of the interfacial activity of polymer-coated gold nanoparticles was performed with the use of a computer-controlled four-roll mill. The nanoparticle locality within the polymeric domains (bulk or interface) was controlled by means of a mixture of polymeric ligands grafted to the gold nanoparticle core. The bulk polymers were polybutadiene (PBd) and polydimethylsiloxane (PDMS). Monoterminated PDMS and PBd ligands were synthesized on the basis of the esterification of reactive groups (such as hydroxyl or amino groups) with lipoic acid anhydride. The formation of polymer-coated nanoparticles using these lipoic acid-functionalized polymers was confirmed via transmission electron microscopy (TEM), and their interfacial activity was manifested as a reduction of the interfacial tension and in the enhanced stability of thin films (as seen via the inhibition of coalescence). The nanoparticles showed an equal, if not superior, ability to reduce the interfacial tension when compared to previous studies on the effect of insoluble surfactants; however, these particles proved not to be as effective at inhibiting coalescence as their surfactant counterpart. We suggest that this effect may be caused by an increase in the attractive van der Waals forces created by the presence of metal-core nanoparticles. Experimental measurements using the four-roll mill allow us to explore the relationship between nanoparticle concentration at the interface and interfacial tension. In particular, we have found evidence that the interface concentration can be increased relative to the equilibrium value achieved by diffusion alone, and thus the interfacial tension can be systematically reduced if the interfacial area is increased temporarily via drop deformation or breakup followed by recoalescence.     

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 .     

Atomic force microscopy reveals hydroxyapatite-citrate interfacial structure at the atomic level

An approach to organic-inorganic interfacial structure at the atomic level is a great challenge in the studies of biomineralization. We demonstrate that atomic force microscopy (AFM) is powerful tool to discover the biomineral interface in detail. By using a model system of (100) hydroxyapatite (HAP) face and citrate, it reveals experimentally that only a side carboxylate and a surface calcium ion are involved in the binding effect during the citrate adsorption, which is against the previous understandings by using Langmuir adsorption and computer simulation. Furthermore, the adsorbed citrate molecules can use their free carboxylate and hydroxyl groups to be self-assembled on the HAP surface. AFM examination also finds that the presence of citrate molecules on the HAP crystal faces can enhance the adhesion force of the HAP surface. We suggest that the established AFM method can be used for a precise and direct understanding of biointerfaces at the atomic level.     

Biodegradable and Biocompatible Silatrane Polymers

In this study, new biodegradable and biocompatible amphiphilic polymers were obtained by modifying the peripheral hydroxyl groups of branched polyethers and polyesters with organosilicon substituents. The structures of the synthesized polymers were confirmed by NMR and GPC. Organosilicon moieties of the polymers were formed by silatranes and trimethylsilyl blocks and displayed hydrophilic and hydrophobic properties, respectively. The effect of the ratio of hydrophilic to hydrophobic organosilicon structures on the surface activity and biological activity of macromolecules was studied, together with the effect on these activities of the macromolecules’ molecular weight and chemical structure. In particular, the critical micelle concentrations were determined, the effect of the structure of the polymers on their wetting with aqueous solutions on glass and parafilm was described, and the aggregation stability of emulsions was studied. Finally, the effect of the polymer structures on their antifungal activity and seed germination stimulation was examined.     

Synthesis and surface activities of multi-ammonium cationics derived from n-octadecyl glycidyl

In this study, cationic surfactants having two, three or four hydroxyl groups were synthesized by the condensation reaction of n-octadecyl glycidyl ether and amine (methyl amine and dimethyl amine) followed by the quaternization with dimethyl sulfate. The structure of a resulting product was determined by ¹H NMR and FT-IR spectroscopies. Interfacial tensions measured as a function of time for n-decane drops brought into contact with 1 wt. % surfactant solutions at 25°C indicated that the interfacial tension decreased over a period of about 10–15 min to an equilibrium value. The results of contact angle measurements indicate that C18-BADM surfactant having four hydroxyl groups is the best wetting agent among others studied. Moreover, the excellent adsorption capacity of C18-BADM system suggests that it can be used as a softening agent during a laundry process. The results of foam stability measurement were consistent with those of CMC and contact angle. The percentage of foam volume decrease was found to increase with the hydrophilicity of a surfactant.