Physicochemical Properties Of Surfactants Research Articles

Interaction of surfactants with Prunus laurocerasus leaf surfaces: time-dependent recovery of wetting contact angles depends on physico-chemical properties of surfactants

BackgroundSurfactants are added to spray solutions because they significantly improve foliar uptake of active ingredients (AIs) into the leaves. It was intended to investigate whether surfactant solutions forming a dried deposit on Prunus leaf surfaces after they were sprayed, lead to structural and functional changes of the cuticle/atmosphere interface. This could potentially result in irreversibly enhanced leaf surface wetting, which should be of major disadvantage. Enhanced wetting could promote leaching of ions and promote leaf surface colonization with microorganisms.ResultsPrunus laurocerasus leaf surfaces were sprayed with aqueous solutions of non-ionic alcohol ethoxylates, a cationic, an anionic and one large polar surfactant. Directly after spraying and drying of the different surfactant solutions, wetting contact angles of deionized water (without surfactant) were significantly lower (between 6 and 54°) compared to wetting contact angles on untreated leaves (77°). Leaf surface wettability with deionized water was more pronounced with non-ionic alcohol ethoxylates (wetting contact angles ranging between 6 and 22°) compared to the other 3 surfactants (wetting contact angles ranging between 42 and 54°). Wetting contact angles of deionized water on leaf surfaces treated with non-ionic alcohol ethoxylates continuously increased again over time resulting in final wetting contact angles not different from untreated leaf surfaces. The time-dependent recovery of wetting contact angles was dependent on the degree of ethoxylation of the non-ionic alcohol ethoxylates. The wetting contact angle recovery rate was lower the higher the degree of ethoxylation of the alcohol ethoxylates was. With the cationic, anionic and large polar surfactant a recovery of wetting contact angles was not observed. In addition, on fully dehydrated and dead leaves wetting contact angle recovery was not observed for any of the tested surfactants after spraying and drying. Analytical determinations of the amounts of alcohol ethoxylates on the leaf surfaces after spraying and drying showed that amounts of alcohol ethoxylates decreased over time on the surface (24–72 h).ConclusionOur results indicate that non-ionic alcohol ethoxylates diffused within hours from the leaf surface into the leaf over time and thus fully disappeared from the leaf surface. This was not the case with the cationic, anionic and the large polar surfactants remaining on the leaf surface.Graphical

Surfactants-mediated the enhanced mobility of tetracycline in saturated porous media and its variation with aqueous chemistry

Knowledge of the mobility of tetracycline (TC) antibiotics in porous media is critical to understand their potential environmental influences. The transport characteristics of TC in sand columns with three different surfactants, including Tween 80, sodium dodecylbenzene sulfonate (SDBS), and didodecyldimethylammonium bromide (DDAB) under various conditions were investigated in this study. Results demonstrated that all surfactants enhanced TC transport under neutral conditions (10mM NaCl at pH 7.0). The observation was attributed mostly to deposition site competition, higher electrostatic repulsion between TC molecules and sand grains, steric hindrance, and the increase of TC hydrophilicity. Furthermore, the order of the transport-enhancement effects was generally observed as follows: DDAB>SDBS>Tween 80. The trend was controlled by the variation in the physicochemical properties of surfactants. It was noticed that the presence of Cu2+ (a model divalent cation) in the background solution, the cation-bridging contributed to the promotion effects of DDAB or Tween 80 on TC mobility. Interestingly, SDBS considerably suppressed TC transport due to the precipitation of SDBS-Cu2+ complexes onto sand surfaces. Moreover, the enhancement order of surfactants at pH 5.0 was similar to that pH 7.0. However, DDAB could inhibit TC transport in sand columns at pH 9.0, which were mainly caused by the decrease of electrostatic repulsion and the hydrophobicity induced by the binding cationic surfactant. Findings from this work provide novel insight into involvement of surfactants in antibiotic transport behaviors in the subsurface environment.

Effect of organic and a Hofmeister series of inorganic counterions on the solvation dynamics and rotational relaxation in aqueous micelles of hexadecyltrimethylammonium surfactants

Abstract The effect of an organic counterion, p-toluenesulfonate (p-TS−) and a Hofmeister series of inorganic counterions, NO3−, Br− and SO42– on the solvation dynamics and rotational relaxation of Coumarin 480 (C-480) in the Stern layer of aqueous micelles of hexadecyltrimethylammonium surfactants (C16TAX) has been studied. Studies have been carried out by means of UV–vis absorption, steady-state fluorescence and fluorescence anisotropy, time-resolved fluorescence and fluorescence anisotropy, and dynamic light scattering measurements. The rate of solvation increases in the order C16TABr > C16TABr > C16TANO3 > (C16TA)2SO4, which is the same as the decreasing order of microviscosity of micelles. The rotational relaxation time is shorter in the micelles of (C16TA)2SO4 as compared to C16TAp-TS as the former micelles have less tightly packed structure than the latter. The slow rotational relaxation is mainly contributed by the lateral diffusion of C-480 along the surface of the micelle. The rotational motion is the slowest for the micelle of (C16TA)2SO4, and the same is the fastest for the micelle of C16TABr. There is an indication of different orientation of C-480 molecules in viscous micelles of C16TAp-TS as compared to other less viscous micelles. The fact of counterion dependent solvation processes might help us for various studies on physicochemical properties of surfactants in solutions.

Molecular dynamics study of micelles properties according to their size

Surfactants are molecules able to spontaneously self-assemble to form aggregates with well-defined properties, such as spherical micelles, planar bilayers, cylindrical micelles or vesicles. Micelles have notably several applications in many domains, such as drug delivery or membrane protein solubilization. In this context, the study of micelle formation in relation with the structural and physico-chemical properties of surfactants is of great interest to better control their use in the different application fields.In this work, we use the MD approach developed by Yoshii et al. and extend it to surfactants with different structures. We aim to systematically investigate different micellar properties as a function of the aggregates size by a molecular dynamics approach, to get an insight into the micellar organization and to collect some relevant descriptors about micelle formation. For this, we perform short MD simulations of preformed micelles of various sizes and analyze three parameters for each micelle size, namely the eccentricity of the micelles, the hydrophobic/hydrophilic surface ratio and the hydrophobic tails hydration. If these parameters are known descriptors of micelles, they were not yet studied in this way by MD.We show that eccentricity, used as “validator” parameter, exhibits minimal values when the aggregate size is close to the experimental aggregation number for surfactants that are known to form spherical micelles. This hence indicates that our methodology gives consistent results. The evolution of the two descriptors follows another scheme, with a sharp increase and decrease, respectively, followed by a leveling-off. The aggregate sizes at which this stabilization starts to occur are close to the respective aggregation number of each surfactant. In our approach, we validate the use of these descriptors to follow micelle formation by MD, from “simple” surfactants to more complex structures, like lipopeptides. Our calculations also suggest that some peculiar behavior, like that of TPC, can be highlighted by our approach.In the context of peptidic surfactants, our methodology could further help to improve computer simulations combined to molecular thermodynamic models to predict micellar properties of those more complex amphiphilic molecules.

In-vivo disposition characteristics of PEG niosome and its interaction with serum proteins

Three different nonionic surfactants (Brij 72, Span 20 and Tween 60) were used to prepare various naked and PEG niosomes. In-vivo study demonstrated that PEGylation dramatically increased the AUC and decreased the affinity to the liver of Brij 72 and Span 20 niosomes in rats. Liver perfusion experiments suggested that the hepatic uptake of naked Brij 72 and Span 20 niosomes could mainly be ascribed to the receptor-mediated uptake, while PEGylation of these niosomes could diminish the receptor-mediated hepatic disposition. Evaluation of serum proteins associated with niosomes revealed that PEGylation of these niosomes significantly reduced the association of serum proteins with them, including typical opsonins such as IgG and C3. On the other hand, in the case of Tween 60 niosomes, naked Tween 60 niosome showed large AUC and its PEGylation did not show any additional effect on the in-vivo pharmacokinetics. Furthermore, PEGylation of Tween 60 niosome did not significantly affect the hepatic disposition or the association of serum proteins with Tween 60 niosome. These results demonstrated that niosomes would exhibit distinct in-vivo disposition characteristics depending on the physicochemical properties of surfactants used and that PEGylation of niosomes with adequate compositions would be a powerful tool to improve their in-vivo behavior.

Using in situ Raman spectroscopy to study the drug precipitation inhibition and supersaturation mechanism of Vitamin E TPGS from self-emulsifying drug delivery systems (SEDDS)

We are reporting a new methodology of using Raman spectroscopy for studying the drug surfactant interactions in self-emulsifying drug delivery systems (SEDDS). The physicochemical properties of surfactants could affect the performance of drugs from lipid delivery systems. Thus the purpose of our research was to study the drug surfactant interactions on a molecular level to understand the mechanism of supersaturation and precipitation inhibition. Two surfactants, Labrasol® and Vitamin E TPGS, were used to formulate several SEDDS. The optimized SEDDS were further evaluated by a kinetic solubility study and in situ Raman spectroscopy for two model drugs. It was found that both drugs precipitated from Labrasol® SEDDS whereas TPGS was able to inhibit precipitation and achieve high drug supersaturation levels. In situ Raman spectroscopy indicated that hydrogen bonding with TPGS was the main factor responsible for inhibiting precipitation. This study was able to correlate the structure and physicochemical properties of the drugs and surfactants to their ability to prevent drug precipitation. Our study brings up a possible new systematic approach by using Raman spectroscopy in the development and optimization of lipid based delivery systems.

Synthesis and physicochemical properties of star-like cationic trimeric surfactants

Efficient synthesis of four star-like triethanolamine based cationic trimeric surfactants Tn (where n is the tail chain length, n=10, 12, 14, and 16) with ester groups in spacers has been successfully achieved, where mild reaction conditions were employed by substituting triethylamine (TEA) with potassium carbonate as the acid binding agent. The physicochemical properties of these surfactants were investigated by means of surface tension, electrical conductivity, and steady-state fluorescence measurements. The trimeric surfactants have been found to be capable of adsorbing to the air/water interface and orienting themselves through the interactions among the hydrocarbon chains. The conductivity measurement revealed the formation of premicellar aggregations in the T16 solution. It is noteworthy that the micropolarity of the surfactant aggregations decreased with the elongation of the hydrophobic chain length. Typically, dynamic light scattering and transmission electron microscopy studies showed that the aggregations of the four surfactants changed from larger ellipsoidal vesicles to smaller globule micelles with the increase of the surfactant concentration. It is assumed that this unusual aggregation behavior is related to the transformation of molecular conformation from stretched configuration to a pyramid-like shape.

Surfactant dithiophosphates lubricating oil additives

This paper presents a research on the tribological properties and the action mechanisms of surfactant lubricating oil additives, polyalkoxy glycol ammonium salts and O,O,S-triesters of polyalkoxy glycol dithiophosphoric acid. To understand the physicochemical properties of surfactants, polyalkoxy glycol dithiophosphoric acid behaviour both in solution and at metal surfaces are identified and discussed. The STM adsorption on steel surface, four-ball and ball disc tests of friction of water, synthetic and mineral oil solutions studies of these additives are presented. Friction and wear properties are dependent on tribological parameters, chemical structure of the additives and their surface active behaviour in tribological systems. The relationships are presented on the example of additives with different molecular structures and masses.

Fundamental Behavior of Model Corrosion Inhibitors

Corrosion inhibition is a complex process of great economic importance that has been addressed in both empirical tests in industry and more detailed experiments in academia. Organic corrosion inhibitors are based on surface‐active compounds, which have been investigated thoroughly in colloid and surface science. In this review, the intention is to connect the physicochemical properties of surfactants to their corrosion‐inhibiting performance. The importance of adequate packing of corrosion inhibitors at the metal surface, as well as how the packing can be improved by co surfactants, is adressed. An investigation of the adsorption of corrosion inhibitor to the oil/water interface showed that the interface is capable of consuming considerable amounts of inhibitor when emulsified. The combination of cationic polymers and anionic surfactant proved to adsorb as a well‐covering film, highly efficient in reducing the corrosion rate. The results are most interesting since it shows that a higher inhibiting efficiency can be achieved even at moderate added amounts of these polymers. This is beneficial from both an economic and environmental point of view.

Effect of Sodium Barbital on the Physico-chemical Properties of Surfactants with Different Charges

The effects of sodium barbital (SB) on the solubility of different kinds of surfactants viz., CTAB (cationic head group), SDS (anionic head group) and Triton X-100 (non ionic head group) in solution phase as well as their first and second critical micelle concentrations (CMC1 and CMC2), the change in Kraft temperatures (TK) and cloud points (CP) have been studied. Furthermore, the article reports SB-surfactant interaction study, which is application oriented and highlights the underlying physico-chemical aspects of the system through florescence and conductivity measurements. The results show that the solubility of CTAB and Triton X-100 increases with the addition of SB, and that of SDS increases in the presence of small amounts of SB and decreases in the presence of large amounts of SB. With the increasing SB concentration, the CMC of CTAB and CMC1 of Triton X-100 both increase, while the CMC of SDS decreases, and the CMC2 of Triton X-100 has no obvious change. The addition of SB decreases the TK of CTAB sharply, but it increases the TK of SDS and the CP of Triton X-100. The different effects of SB on the physico-chemical properties of differently charged surfactants may be related to its different interactions with the surfactants.

Hydrolyzable nonionic surfactants: Stability and physicochemical properties of surfactants containing carbonate, ester, and amide bonds

A linear and a branched nonionic cleavable surfactants containing a carbonate bond have been prepared from tetra(ethylene glycol) and an alkylchloroformate. The stability of these carbonate surfactants was determined by investigating their hydrolysis and biodegradability characteristics. The hydrolysis was catalyzed by alkali or enzymes (esterase from porcine liver and lipases from Mucor miehei and Candida antarctica B) and was monitored using 1H NMR. It was found that the stability toward alkali was higher for a carbonate surfactant than for a corresponding surfactant with an ester as weak bond. Biodegradation tests resulted in more than 60% degradation after 28 days for both carbonate surfactants. Physicochemical properties, such as critical micelle concentration (CMC), cloud point, area per molecule, and surface tension at the CMC, were determined and compared to those obtained from similar surfactants containing ester, amide, or ether bonds. It was found that the carbonate linkage is hydrophobic and that the oxycarbonyl part of the carbonate group is equivalent, in a formal sense, to an extra methylene group in the alkyl chain of the surfactant.

Surfactants and experimental irritant contact dermatitis.

Surface-active agents (surfactants) are characterized by the possession of 2 different moieties, both polar and non-polar regions on the same molecule. Surfactants are broadly classified as anionic, cationic, amphoteric, or non-ionic, according to the nature of the hydrophile yielded in aqueous solution. In currently marketed household, personal, and industrial cleaners, anionic surfactants are the most common class because of their relative ability to solubilize fats and oils, lower the surface tension of aqueous solutions, or form microemulsions. Many surfactants elicit irritant reactions when applied to the skin, partially due to their relative ability to solubilize lipid membranes. Hence, surfactants have become important implements in skin irritation investigations. In general, the physicochemical properties of surfactants are a crucial factor in eliciting skin irritation. Anionic surfactants are broadly accepted as potent irritants to human and animal skin. Cationic surfactants are reputedly at least equally irritating, but more cytotoxic than anionic, while the irritation potential of non-ionic surfactants is considered the lowest. Such classification of innumerable surfactants is convenient and held in high practical esteem. however, the categorization does not permit the exact determination of irritation and cytotoxicity potential of each surfactant. Ranking of surfactant skin irritancy and cytotoxicity obtained by both in vitro and in vivo assays provides a helpful orientation for future work.

Performance and physicochemical properties of α‐sulfo fatty acid methyl esters

The detergency properties of α‐sulfonated fatty acid methyl esters (α‐SFMe) were evaluated and compared to those of conventional anionic surfactants by using a model heavy‐duty detergent formulation. Several physicochemical properties of surfactants were measured to investigate the effective factors on detergency. α‐SFMe showed good detergency performance under various washing conditions. These results were considered to correlate well with the good adsorption behavior on oils and dispersing capabilities for particles, as well as with the good solubilization capacity. Solubilization behavior of α‐SFMe is discussed in relation to micelle properties. It is suggested that α‐SFMe can form suitable micelles for solubilizing polar oils advantageously, due to its bulky hydrophilic group.

A study of the interaction of natural polymers — surfactants I. International of catalase (EC 1.11.1.6) with ionic surfactants

Catalase interaction with anionic type (sodium laurate and sodium dodecylsulfate) and cationic type (dodecylpyrimidinium chloride) surfactants was investigated. Viscosity, electric conductivity, enzyme activity and kinetics depend on surfactant concentration. Corroborating data demonstrate the existence of interaction between catalase and anionic surfactants. Results were interpreted in the terms of non-polar interactions, taking into account both the physicochemical properties of surfactants in aqueous solutions and the better known structure of haemic proteins (haemoglobin) similar to catalase.

Effect of Micellar Size on Physicochemical Properties of Surfactants

Effect of Micellar Size on Physicochemical Properties of Surfactants