Synthesis and Properties of Alkoxyethyl β‐d‐Xylopyranoside

In order to improve the water solubility of sugar‐based surfactants, alkyl β‐d‐ xylopyranosides, novel sugar‐based surfactants, 1,2‐trans alkoxyethyl β‐d‐ xylopyranosides, with alkyl chain length n = 6–12 were stereoselectively prepared by the trichloroacetimidate method. Their properties including hydrophilic–lipophilic balance (HLB) number, water solubility, surface tension, emulsification, foamability, thermotropic liquid crystal, and hygroscopicity were investigated. The results indicated that their HLB number decreased with increase of alkyl chain, the water solubility improved since the hydrophilic oxyethene (─OCH₂CH₂─) fragment was introduced. The dissolution process was entropy driven at 25–45 °C for alkyl chain length n = 6–10. Octyloxyethyl β‐d‐ xylopyranoside had the best foaming ability. Nonyloxyethyl β‐d‐ xylopyranoside had the best foam stability and the emulsifying ability was better in toluene/water system than in rapeseed oil/water system. The surface tension of in aqueous solution dropped to 27.8 mN m^?1 at the critical micelle concentration, and it also showed the most distinct thermotropic liquid phases with cross pattern texture upon heating and the fan schlieren texture on cooling. Hexyloxyethyl β‐d‐ xylopyranoside possessed the strongest hygroscopicity. Based on the effective improvement of water solubility, the prepared alkoxyethyl β‐d‐ xylopyranosides showed excellent surface activity and are expected to develop their practical application as a class of novel sugar‐based surfactants.     

Synthesis and Properties of Alkyl <Emphasis Type="Italic">β</Emphasis>-<Emphasis Type="SmallCaps">d</Emphasis>-Galactopyranoside

A series of alkyl β-d-galactopyranosides were prepared by the trichloroacetimidate method with d-galactose and alcohols with different chain lengths as raw materials. Their solubility, surface tension, emulsification, foaming, wettability, thermotropic liquid crystalline properties, and thermal stability were investigated. Alkyl β-d-galactopyranosides are soluble in water and ethanol, and the solubility decreases with increasing alkyl chain length. Decyl β-d-galactopyranoside was insoluble in water, but soluble in ethanol. Dissolution of alkyl β-d-galactopyranoside in water is an endothermic process with dissolution enthalpies greater than zero. Nonyl β-d-galactopyranoside had an excellent emulsifying property, better foaming ability and the best foam stability. The CMC values of alkyl β-d-galactopyranosides decrease with increasing of alkyl chain length. Alkyl β-d-galactopyranosides are thermally stable up to 270 °C. Alkyl β-d-galactopyranosides show the distinctive optical texture of a thermotropic liquid crystal smectic A type phase. Decyl β-d-galactopyranoside showed the strongest wettability.     

The Irritant Effects of Pharmaceutically Applied Surfactants

Dermal or transdermal medication may lead to irritant contact dermatitis. However, little information is available on the irritant effect of surfactants which are applied in topical formulations. Our aim was to examine the irritant effect of the most frequent compounds in topical products. A murine model was applied. The following compounds were examined: sodium lauryl sulphate (SLS), polyethoxylated (40EO) hydrogenated castor oil and sucrose laurate. SLS led to severe erythema, increase in transepidermal water loss (TEWL) and induced necrosis and accumulation of neutrophylic granulocytes and lymphocytes. Exposure to sucrose laurate resulted in an elevation of TEWL, but histology did not reveal impairment of the skin structure. Application of polyethoxylated (40EO) hydrogenated castor oil was not accompanied by tissue damage. Special attention should be paid to the irritant effect of SLS. Polyethoxylated (40EO) hydrogenated castor oil seems to be a non-irritant agent and sucrose laurate is also a promising candidate for application in topical preparations.     

Alkyl Xylosides: Physico‐Chemical Properties and Influence on Environmental Bacteria Cells

A group of four selected non‐ionic surfactants based on carbohydrates, namely octyl d ‐xyloside (C₈X), nonyl d ‐xyloside (C₉X), decyl d ‐xyloside (C₁₀X) and dodecyl d ‐xyloside (C₁₂X), have been investigated to accomplish a better understanding of their physico‐chemical properties as well as biological activities. The surface‐active properties, such as critical micelle concentration (CMC), emulsion and foam stability, the impact of the compounds on cell surface hydrophobicity and cell membrane permeability together with their toxicity on the selected bacterial strains have been determined as well. The studied group of surfactants showed high surface‐active properties allowing a decrease in the surface tension to values below 25 mN m^?1 for dodecyl d ‐xyloside at the CMC. The investigated compounds did not have any toxic influence on two Pseudomonas bacterial strains at concentrations below 25 mg L^?1. The studied long‐chain alkyl xylosides influenced both the cell inner membrane permeability and the cell surface hydrophobicity. Furthermore, the alkyl chain length, as well as the surfactant concentration, had a significant impact on the modifications of the cell surface properties. The tested non‐ionic surfactants exhibited strong surface‐active properties accompanied by the significant influence on growth and properties of Pseudomonas bacteria cells.     

Aggregation and Adsorption Behavior of Cationic Surfactants (Cetyltrimethylammonium Bromide and Dodecyltrimethylammonium Bromide) in Aqueous Solutions of Antibiotic Drug (Amikacin Sulphate) at Different Temperatures

Conductivity and spectroscopy techniques have been accomplished to comprehend the mechanism of supramolecular assembly of cetyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium bromide (DTAB) in aqueous solution of amikacin sulphate (0.001, 0.005, and 0.010 mol kg⁻¹). For CTAB, the normal boost of the CMC value with rise in temperature manifests the significant role of aquaphilic dehydration. However, the aquaphobic dehydrations become prominent with temperature and depict typical U-shaped behavior of CMC for DTAB. The thermodynamic parameters of micellization have been derived from CMC values. The outcomes have been conferred in terms of solvation of hydrophobic part of surfactants by hydrophobic part of amikacin sulphate and micellization becomes more favorable for surfactant with more hydrophobic character in the presence of drug. The alteration in micro-environment of the ternary (drug/surfactant/water) system has been explained in terms of fluorescence emission intensity of surfactant solutions which has been found to decrease by the addition of drug. The obtained absorbance spectrum by varying concentrations of surfactant/drug affords noteworthy information regarding the diverse interactions in studied systems. Moreover, the exhaustive understanding of surfactant micellar behavior have been discussed in consideration of use of surfactants as drug delivery agents and hence to amplify drug bioavailability consequently remodeling its treatment efficacy.     

Counterion Effect on Krafft Temperature and Related Properties of Octadecyltrimethylammonium Bromide

In the present work, we have investigated the effect of some counterions on the Krafft temperature (T _K) and the micelle formation of octadecyltrimethylammonium bromide (OTAB) in aqueous solution. The results showed that the ions with more chaotropic nature increase the T _K while those with a kosmotropic, hydrotropic and less chaotropic nature lower the T _K of the surfactant. More chaotropic SCN^? and I^?, being weakly hydrated, form contact ion pairs with the octadecyltrimethylammonium ion and reduce the electrostatic repulsion between the surfactant molecules. As a result, these ions exhibit salting out behavior and raise the T _K of the surfactant. On the other hand, less chaotropic Cl^? and NO₃ ^?, kosmotropic SO₄ ^2? and F^? and hydrotropic benzoate and salicylate ions increase the solubility of the surfactant, with a consequent decrease in the T _K. SO₄ ^2?, F^?, benzoate and salicylate cannot form contact ion pairs with the weakly hydrated cationic part of OTAB. Rather, being extensively hydrated and kosmotropic in nature, these ions do not show any tendency to shed their hydrated water molecules to form contact ion pairs with the weakly hydrated octadecyltrimethylammonium ion and therefore, stay apart. As a result, the T _K of the surfactant decreases significantly in the presence of these ions. The critical micelle concentration (CMC) of the surfactant decreases significantly in the presence of these ions due to screening of the micelle surface charge by the added counterions. Consequently, the surfactant molecules attain better packing because of substantial reduction in the electrostatic repulsion between the charged head-groups, showing a significant decrease in the CMC.     

Ionic Behavior Assessment of Surface-Active Compounds from Corn Steep Liquor by Exchange Resins

Depending on their ionic nature, biosurfactants can be classified as nonionic, anionic, cationic, or amphoteric. The ionic behavior of biosurfactants is an important characteristic that dictates their use in industrial applications. In this work, a biosurfactant extract obtained from corn steep liquor was subjected to anionic or cationic resins, in order to study the ionic behavior under different operational conditions using response surface methodology. The independent variables included in the study are the dilution of biosurfactant solution, the amount of cationic or anionic resin, and the extraction time, whereas the dependent variables studied consisted of the surface tension of biosurfactant aqueous solution, after contacting with anionic or cationic resin. The results showed that biosurfactant extracted from corn steep liquor is amphoteric, since both resins were able to entrap this biosurfactant, making it particularly suited for use in personal care preparations for sensitive skin.     

Solution Properties of Alkyl β-D-Maltosides

Alkyl β-D-maltosides are an important class of sugar-based nonionic surfactants and have been widely studied. Nevertheless, it is still necessary to investigate further their amphiphilic structure-surface property relationships. In this article, we reported a series of properties of synthetic alkyl β-D-maltosides ( 6a – 6i , n = 6–18) including their hydrophilic–lipophilic balance (HLB) number, water solubility, hygroscopicity, moisture-retention capacity, foaming ability, surface tension, thermotropic phase behavior, and skin irritation. Their HLB number and water solubility decreased with increasing alkyl chain length. Hexyl β-D-maltoside exhibited the strongest hygroscopicity and moisture-retention capacity. Decyl β-D-maltoside and dodecyl β-D-maltoside possessed excellent foaming power and foaming stability. Furthermore, the critical micelle concentration (CMC) of alkyl β-D-maltoside ( 6a – 6g , n = 6–14) and their surface tension at CMC decreased with increasing alkyl chain length. At last, alkyl β-D-maltosides ( 6a – 6g ) should be considered as safe surfactants by the skin irritation assessment.     

Ecotoxicological Assessment of Mixtures of Ether Carboxylic Derivative and Amine-Oxide-Based Non-ionic Surfactants on the Aquatic Environment

The purpose of this study was to discuss the effect of the chemical structure of anionic and non-ionic surfactants and surface activity on toxicity. Single and binary mixtures of three ether carboxylic derivative surfactants and three amine-oxide-based non-ionic surfactants were used. Toxicity was determined using three test organisms: freshwater crustaceans (Daphnia magna), luminescent bacteria (Vibrio fischeri), and microalgae (Selenastrum capricornutum). The toxicity of surfactants is related to the hydrophobic alkyl chain, the degree of ethoxylation, and the critical micelle concentration of surfactants. Relationships found agreed with the fact that the lower toxicity is shown by the shorter alkyl chain. There is a strong relation between surface activity and toxicity: the toxicity increased as the CMC of the surfactant or mixtures of surfactants decreased. Commercial products are formulated using surfactants mixtures, so it is important to know their behavior using an easily measured property: the least toxic mixtures were formed by the surfactants having lower individual toxicity. Around the CMC, our data show a synergism for the binary mixtures. The results have given rise to a classification of the different surfactants and their mixtures according to the organism test, as safe, harmful or toxic. V. fischeri was in general the most sensitive microorganism to the toxic effect of the surfactants, followed by Daphnia magna, while Selenastrum capricornutum was more tolerant. These results can be useful for selecting technically efficient surfactants and their mixtures with a lower ecotoxicity on the aquatic environment.     

Application of Acoustic Spectroscopy to the Characterization of Surfactant Solutions,Emulsions, and Microemulsions: d–Limonene–Water–C12EO7–Isopropanol System

The application of acoustic spectroscopy to the characterization of binary C₁₂EO₇—water system was studied. It was discovered that the size of micelles in aqueous surfactant solutions could not be determined, but it was possible to determine the size of water nanodomains existing in the surfactant-rich systems. It was suggested that in colloidal systems, the energy of ultrasonic waves is dissipated only by interfaces existing between condensed phases. The characterization of Winsor transitions by acoustic spectroscopy in water/d-limonene system stabilized by a mixture of nonionic surfactant and isopropyl alcohol (cosolvent) was also explored. In one study, systems with a constant d-limonene to water weight ratio obtained in the course of titration of d-limonene-in-water emulsion with increasing amounts of surfactant+alcohol were investigated. In another study, a balanced d-limonene/water microemulsion was sequentially diluted with water and d-limonene. The transition between Winsor I and Winsor IV systems was monitored in both cases. Droplet size distributions were calculated using different models for dispersed and continuous phase composition. It was demonstrated that the magnitude of acoustic scattering played a significant role in the ability to reliably determine droplet size distributions, and in particular to simultaneously observe nanometer-size and micron-size droplets in Winsor I systems. An attempt was made to account for intrinsic attenuation of surfactant and alcohol by associating them with the aqueous phase, but this approach was shown not to be applicable in the case of Winsor IV microemulsions.     

Ozonation of Anionic and Non-ionic Surfactants in Aqueous Solutions: Impact on Aquatic Toxicity

The objective of this study was to investigate the influence of ozonation of anionic and non-ionic surfactants on their aquatic toxicity. Toxicity values of various commercially important anionic and non-ionic surfactants have been determined using the luminescent bacterium Vibrio fischeri. Surface tension measurements were made to study the interfacial activity. The behavior depends on the chemical structure. Some intermediate ozonation products were found to be more toxic than the base surfactant and others were found to be less. Surfactants with aromatic rings such as linear alkyl benzene sulfonates, or surfactants with glycosidic groups such as alkylpolyglucosides, exhibit a lower toxicity after ozonation. On the other hand, ether groups present in the fatty-alcohol ethoxylates and ether carboxylic derivative surfactants, and carboxylic acid derivates present in the ether carboxylic derivative surfactants lead to increasing toxicity after ozonation. Surfactants with ether groups probably formed short-chain polyethoxylated compounds and carboxylic acids, which are possibly responsible for the surface-tension decrease that promotes the toxicity increase.     

Interaction Between an Anionic and an Amphoteric Surfactant. Part II: Precipitation

Use of amphoteric and anionic surfactants is very common in practical formulations such as shampoos and hand dishwashing products. Precipitation of mixtures of dimethyldodecylamine oxide (DDAO) as an amphoteric surfactant and sodium dodecyl sulfate (SDS) as an anionic surfactant were studied at different pH levels. The DDAO is a pH-sensitive surfactant and its protonation can be expressed in terms of a pK _a similar to an acid dissociation constant. The protonated form of DDAO carries a positive charge and precipitates with the oppositely charged SDS. Therefore, precipitation phase boundaries are pH dependent due to the varying degree of DDAO protonation. By combining the use of regular solution theory and the pseudophase separation model to describe micellar mixing nonidealities with the precipitate solubility product constant and the protonation dissociation constant, a model to predict the precipitation phase boundary is presented here. The model agrees well with experimental phase boundaries at different pH levels.

Studies on Solution Behavior of Aqueous Mixtures of Nonionic Polymer in Presence of Cationic Surfactants

The interactions of two gemini surfactants (16–s–16, s = 5, 6) and their conventional counterpart cetyltrimethylammonium bromide (CTAB) with polyethylene glycols (PEG 3000 and PEG 35000) have been investigated using conductivity, steady state fluorescence, viscosity and TEM techniques. The results indicate that there is no interaction between the PEG 3000/CTAB complex at lower polymer concentrations. However, a very weak interaction is observed at higher concentrations (0.5 and 1.0 wt% PEG 3000), while PEG 3000 and PEG 35000 interact with the gemini surfactants. Both critical aggregation concentration (CAC) and critical micelle concentration (CMC) increases with polymer concentration but are independent of the polymer molecular weight. From steady state fluorescence it is found that the addition of PEG results in no drastic decrease in the aggregation number (N) for all surfactants. This suggests that the atmosphere surrounding the polyion-bound micelles, with respect to the influence on the forces acting at the micelle surface, is equivalent to the counterion/water atmosphere surrounding free micelles. The relative viscosity (η _r) results show an enhancement in η _r for all the surfactants. The increase in η _r is quite significant with gemini surfactants. Polymer-surfactant interaction also depends on the polymer molecular weight. Also, the interaction seems to affect both inter polymer–polymer association as well as chain expansion. Additionally the surfactant induced changes in the polymer conformation depicted by TEM study at the micro structural level confirmed previously observed interactions determined by different analytical techniques.     

A 1D- and 2D-NMR Study of an Anionic Surfactant/Neutral Polymer Complex

NMR chemical shifts and linewidth measurements were examined for mixtures of sodium 10-phenyldecanoate (Na ω-PhDec) in deuterated aqueous solutions in the presence of varying compositions of poly(ethylene oxide) (PEO) polymers of 2000 and 4000 molecular weight. In addition, variable temperature NMR spectra and NMR spin lattice relaxation times (T ₁) were obtained for the PEO-4000/Na ω-PhDec system as a function of varying polymer concentrations. As expected, the polymer/surfactant systems exhibit the behaviour typical of that of an anionic surfactant/neutral polymer system with well defined critical aggregation concentrations (CMC) corresponding to the formation of polymer/surfactant complexes below the CMC of the free surfactant. The ¹H-NMR linewidths acquired for the Na ω-PhDec/PEO-4000 system before and after the CMC region of the surfactant indicate that the maximum in the linewidth of the PEO proton peak is reached at approximately twice the CMC of the free surfactant. 2D-NMR NOESY measurements on this system exhibit cross peaks between the PEO protons and the protons on the surfactant backbone, consistent with the location of the phenyl group in the micellar interior. All these NMR experiments are interpreted in terms of the structure of the polymer/surfactant complexes as a function of the system composition.

Dissolution of Soap Scum by Surfactant Part I: Effects of Chelant and Type of Soap Scum

The equilibrium solubilities of two model soap scums [calcium stearate and magnesium stearate: Ca(C₁₈)₂ and Mg(C₁₈)₂] were measured in aqueous solutions containing three different types of surfactants: methyl ester sulfonate (MES) as an anionic; alcohol ethoxylate (EO9) as a nonionic; and dimethyldodecylamine oxide (DDAO) as an amphoteric with and without a chelating agent [disodium ethylenediaminetetraacetate (Na₂EDTA)]. The solubility of calcium soap scum was generally higher than that of magnesium soap scum, the exception being some DDAO systems. The use of the DDAO surfactant with the Na₂EDTA chelating agent at high pH gives the highest solubilities of both studied soap scums. The soap scum solubility is on the order of 2,000 times that in water at high pH. The DDAO is the most effective surfactant under all conditions. The MES is more effective than the EO9 at low pH with the opposite trend observed at high pH. The synergism from added chelant is generally greater at higher pH and is greatest for DDAO followed by EO9.     

Catalysts for the Ethoxylation of Esters

The intermediates for the production of nonionic surfactants can be derived from petrochemicals and/or from renewable raw materials. In both, the role of catalysis is fundamental. In this paper the main results reported in the literature related with the catalysis for ethoxylation of fatty esters will be reviewed. The main open challenges for these technologies will be outlined.     

Synthesis,Characterization, and Evaluation of Surface and Thermal Properties and Cytotoxicity of 2-Hydroxy-3-Phenoxypropyl Imidazolium Bola-Type Gemini Amphiphiles

A library of imidazolium-based gemini cationic bola amphiphiles was synthesized using a regioselective ring-opening reaction of glycidyl phenyl ether with imidazole under solvent-free conditions. The corresponding hexafluorophosphate (PF₆⁻) and tetrafluoroborate (BF₄⁻) counterion-containing amphiphiles were also synthesized and characterized using nuclear magnetic resonance (NMR) and mass spectroscopy. The micellar and interfacial parameters like the critical micelle concentration (CMC), surface pressure at the CMC (П_cmc), surface tension at CMC ( γ_cmc ), counterion binding (β), maximum surface excess concentration ( Γ_max ), minimum area per molecule ( A_min ), standard free energy of micellization () and adsorption (), and Kraft temperature were evaluated using surface tension and conductometry methods in aqueous solution as well as in buffer solution. Dynamic light scattering (DLS) was used to determine the size of the micelles formed in the aqueous solution. Cytotoxicity tests were carried out on the C6 glioma cancerous brain cell line using the MTT assay (3-(4, 5-dimethylthiazole-2-yl)-2, 5-diphenyltetrazolium bromide) to evaluate the IC₅₀ value of all the synthesized amphiphiles. Thermal stability of these amphiphiles was also evaluated using a thermal gravimetric analyzer (TGA). Economic way of synthesis, moderate thermal stability, a low value of CMC, and cytotoxicity of these amphiphiles will inspire new research in the field of nanobiotechnology and pharmaceutical industries.     

Synthesis,Characterization and Evaluation of Surface and Thermal Properties of 3‐Cyclohexyloxy‐2‐Hydroxypropyl Pyridinium and Imidazolium Surface‐Active Ionic Liquids

In this work, 1‐halo‐3‐(cyclohexyloxy)propan‐2‐ol ( 3a/3b ) were reacted with N‐methylimidazole ( 4 ) or pyridine ( 5 ) to yield the respective 3‐(3‐(cyclohexyloxy)‐2‐hydroxypropyl)‐1‐methyl‐1H‐imidazol‐3‐ium ( 6a/6b ) or pyridinium ( 7a/7b ) surface‐active ionic liquids (SAIL). The self‐aggregation behavior of these ionic liquids (IL) was evaluated by conductometric and tensiometric methods. The thermal stability and size of the micelles were determined by thermogravimetric analysis and dynamic light scattering studies, respectively. The investigated IL were found to exhibit very low cytotoxicity as evaluated by MTT (3‐(4, 5‐dimethylthiazol‐2‐yl)‐2, 5‐diphenyltetrazolium bromide) assay on the C6 glioma cell line, indicating that the investigated SAIL can be considered for biological applications like drug and gene delivery. The conventional IL 3‐methyl‐1‐octyl imidazolium bromide ( C ₈ mimBr ) was used for comparison in property evaluations.     

Combined Use of Ozonation and Biodegradation of Anionic and Non-ionic Surfactants

This study investigated the extent of primary and final biodegradation of anionic and non-ionic surfactants to evaluate the combined use of ozonation and biodegradation in surfactant removal. The surfactants used were alkylpolyglucosides and linear alkyl benzene sulfonates. The anionic surfactant containing a benzene ring on its structure was oxidized faster than was the non-ionic surfactant. Both surfactants showed poor mineralization due to ozonation indicating an ozone attack primarily on carbon bonds. The results indicate that the removal of surfactants and of the total organic carbon is increased by the consecutive use of ozonation and biodegradation.     

Analytical Characterization and Comparison of Tristyrylphenol Ethoxylates Used in Agrochemical Formulations

Tristyrylphenol ethoxylates are a group of technical nonionic surfactants that contain no single defined molecule but have a polymeric distribution with an average of 3 styrene and 16 ethylene oxide units. To analyze differences in the ethylene oxide distribution of the surfactant from various suppliers, and thus to specify more precisely the required quality for its use in agrochemical formulations, an analytical method was developed using liquid chromatography coupled to time‐of‐flight mass spectrometry with exact mass measurement in combination with multivariate data analysis. The method investigated here enables a fast and comprehensive characterization and comparison of the tristyrylphenol ethoxylates from different sources. The batches showed significant differences among suppliers with regard to composition and content of by‐products. Differences include the content of the different styrenated phenol ethoxylates (e.g., mono‐, di‐, tri‐, and tetrastyrylphenol ethoxylates) and of mono‐ and distyrylphenol copolymerized propoxylates–ethoxylates. The supplier of a given sample could be traced based on these differences by using a combination of principal component analysis and hierarchical clustering analysis. This was possible using either the raw material or a model agrochemical formulation containing the surfactant.