Surfactant properties of purified polyglycerol monolaurates

A series of purified polyglycerol monolaurates (PGML), such as di-, tri-, tetra-, and pentaglycerol monolaurates, were synthesized, and their surfactant properties in aqueous solutions were examined. The surfactant properties of PGML were compared with those of n-dodecyl polyoxyethylene monoethers (C₁₂EO_n) to examine the function of the hydrophilic part of these compounds. The critical micelle concentration (CMC) values and the surface tension at CMC of PGML and C₁₂EO_n increased linearly with an increase in the number of glycerol and oxyethylene units, respectively; the slope of the increase was greater for PGML than C₁₂EO_n. The minimum surface area per molecule of PGML was smaller than that of C₁₂EO_n at the air/aqueous solution interface. The initial foam heights of the surfactants at the CMC increased with an increase in the number of glycerol or oxyethylene units, and the foam heights of PGML were consistently higher and more stable than those of C₁₂EO_n. Detergency depended on a reduction in interfacial tension. Triglycerol monolaurate showed the lowest interfacial tension and the highest detergency among all the surfactants tested. Overall, the PGML showed better performance in all the surfactant properties tested than C₁₂EO_n. It is noteworthy that the surfactant properties of PGML having few glycerol units (di- to tetraglycerol monolaurates) are on par with those of C₁₂EO_n having many oxyethylene units (hexa- and octaoxyethylene). These results suggest that PGML having a secondary hydroxyl group on every glycerol unit of the hydrophilic part could be more hydrophilic than C₁₂EO_n; this characteristic feature guaranteed the superior surfactant properties of PGML.     

Synthesis and Surface Properties Characterization of Perfluoroalkylated Oligo(oxyethylene)glycols

A series of perfluoroalkylated oligo(oxyethylene) glycols as non-ionic fluorinated surfactants was prepared. The synthesis was performed by adding a molecule of a oligo(oxyethylene)glycol of the general formula HO(CH₂CH₂O)_nOH (n = 1, 2, 4, 6.4, 22.3) to 2-(perfluorooctylmethyl) oxirane in the presence of catalytic amounts of a Lewis acid. This procedure led to the formation of an amphiphilic molecule characterized by an hydrophobic lipophobic perfluorinated tail and hydrophilic non-ionic oligo(oxyethylene)chain. Infra red spectroscopy, mass spectroscopy and multinuclear NMR spectroscopy allowed the chemical characterization of the synthesized compounds to be made. Critical micellar concentration, surface tension, interfacial tension and cloud point measurements carries out on aqueous solutions allowed us to evaluate the surface and interfacial properties of the perfluoroalkylated oligo(oxyethylene)glycols. In addition, surface pressure-area (π, A) diagrams allowed us to determine the principal parameters characterizing the state of their monolayers. The aim of the work was to investigate the effect of the hydrophilic chain length on physical and surface properties.     

Effect of Polyoxyethylene Chain Length on the Physicochemical Properties of N,N‐Dimethyl‐N‐dodecyl Polyoxyethylene Amine Oxide Hybrid Surfactants (C12EOnAO,with n = 1–4)

In order to determine the structure‐performance relationship of nonionic‐zwitterionic hybrid surfactants, N,N‐dimethyl‐N‐dodecyl polyoxyethylene (n) amine oxides (C₁₂EO_nAO) with different polyoxyethylene lengths (EO_n, n = 1–4) were synthesized. For homologous C₁₂EO_nAO, it was observed that the critical micelle concentration (CMC), the maximum surface excess (Γ_m), CMC/C₂₀, and the critical micelle aggregation number (N_m,c) decreased on going from 1 to 4 in EO_n. However, there were concomitant increases in surface tension at the CMC (γ_CMC), minimum molecular cross‐sectional area (A_min), adsorption efficiency (pC₂₀), and the polarity ([I₁/I₃]_m) based on the locus of solubilization for pyrene. The values of log CMC and N_m,c decreased linearly with EO_n lengthening from 1 to 4, although the impact of each EO unit on the CMC of C₁₂EO_nAO (n = 1–4) was much smaller than that typically seen for methylene units in the hydrophobic main chains of traditional surfactants. Compared to the structurally related conventional surfactant N,N‐dimethyl‐N‐dodecyl amine oxide (C₁₂AO), C₁₂EO_nAO (n = 1–4) have smaller CMC, A_min, and CMC/C₂₀, but larger pC₂₀, Γ_m, and N_m,c with a higher [I₁/I₃]_m. This may be attributed to the moderately amphiphilic EO_n (n = 1–4) between the hydrophobic C₁₂ tail and the hydrophilic AO head group.     

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.     

Polymeric surfactants for enhanced oil recovery. Part V: Prediction models for the effect of temperature and length of polyoxyethylene chain or hlb on surface and thermodynamic properties of some ethoxylated polymeric nonionics

Several equation models were investigated to find the relationship between temperature (T). number of ethylene oxide (EO) units (n) or the hydrophile-lipophile balance (HLB) and the surface and thermodynamic properties of some ethoxylated alkylphenol-formaldehyde polymeric nonionic surfactants. These properties include critical micelle concentration (CMC), free energy of micellization (ΔG_mic), surface tension at CMC (7_CMC), effectiveness (γ_CMC) and efficiency (pC₂₀) of surfactant to reduce the surface tension of water. The values of the ratio CMC/C_{2(π = 20)} were also considered. The linear multiple regression technique was employed to determine the parameters of the equations and to choose the best forms with the highest values of R² and F-ratio which reflect the goodness and the reliability of the fit.     

Forecasting the cloud point of alkoxylated nonionic surfactants

The highest effectiveness of detergency for nonionic surfactants is observed in the proximity of the cloud point. This phenomenon is primarily influenced by surfactant molecular structure, such as carbon chain length and type of the hydrophilic components. Target of this investigation is to identify a relationship between the cloud point and the structure of nonionic surfactants based on ethoxylated (C_nE_m), ethoxylated-propoxylated (C_nE_mP_p) and propoxylated-ethoxylated (C_nP_pE_m) fatty alcohols. Three hundred and fifty nonionic surfactants have been prepared for this purpose. These surfactants differ in the C-chain lengths, C₄/C₆ to C₂₀/C₂₂, and the amount of ethylene oxide (EO range [n] 2–22 ethoxylation) and propylene oxide (PO range [p] 0–12 propoxylation) moieties. Mapping the differences in the performance allows us to propose a high-accuracy topological model describing the structure influence on the cloud point.     

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.     

Properties of a Binary System Containing Anionic and Cationic Gemini Surfactants

Surface tension, fluorescence, and dynamic light scattering were used to investigate the properties of a binary surfactant system comprising an anionic gemini surfactant (DLMC) and cationic gemini surfactant (II‐12‐EO₂). Surface tension measurements afforded the critical micelle concentration (cmc) of the mixture and the values are all lower than those of pure constituent surfactants. For the mixtures of II‐12‐EO₂/DLMC, the micelle aggregation number decreases with the increase of II‐12‐EO₂, and the micropolarity of the micelle is lowest when the molar fraction of II‐12‐EO₂ is 0.5; the hydrodynamic radius (R_h) of the mixed micelle first increases and then decreases with the addition of II‐12‐EO₂, and larger micelles are obtained when the molar fraction of II‐12‐EO₂ is 0.5 or 0.7.     

Oil splitting in industrial cleaning systems as studied by conductivity and interfacial tension

Characteristics of emulsion formation and splitting into aqueous and oily phases in simple and formulated surfactant systems were studied via conductivity. In systems composed of mixed nonionic ethoxylated alcohol surfactants, K₂CO₃, and emulsified n-hexadecane, conductivity decreased linearly with increasing oil volume fraction at HLB (hydrophile-lipophile balance) values of 12.9 and 13.9. The slope of the plot was ca. −3/2, in agreement with the Maxwell expression. At values less than or equal to an HLB of 11.3, conductivity first increased with a small addition of oil and then decreased nearly linearly with subsequent amounts. This was probably due to low HLB surfactants partitioning into the oily phase. When the type of oil was varied, the reduced conductivity also decreased linearly with volume fraction of emulsified oil. The slope was ca. −3/2 for oil weights ranging from very light (n-hexadecane) to very heavy (80W–90 gear oil), also in agreement with the Maxwell expression. Oil separation rates were measured by monitoring the change in conductivity in the lower region of the emulsion (where the aqueous layer formed) during splitting of the oily phase. Heavier oils were found to separate faster than light oils. Oils containing lubricity agents split at the slowest rate. Systems with lower HLB surfactants also displayed slower splitting rates. Splitting rates for a variety of systems, from simple oil and saline systems to more complex formulated systems, over temperatures from 23 to 75°C, were related to oil-aqueous interfacial tension values through a power law expression composed of the maximum splitting rate and the interfacial tension between saline and oil at 23°C.     

Synthesis and Study of the Surface Properties of Alkylnaphthalene and Alkylphenanthrene Sulfonates

Some alkylnaphthalene and alkylphenanthrene sulfonates were synthesized by means of a Wurtz–Fittig reaction. The HLB values for the prepared compounds were calculated, and the basic properties were studied in water at different temperatures, namely, 25, 35 and 45 °C. Through surface tension measurements, the following values were determined: the critical micelle concentration (CMC) and the surface tension at the CMC (γ_CMC). The following values were calculated: area per molecule at the CMC (A_CMC), standard free energy change of micellization (ΔG _mic), standard free energy of adsorption (ΔG _ad), and the efficiency of a surfactant in reducing surface tension (pC20). Furthermore, the partition coefficients of the synthesized compounds were also measured. The results show that n-alkylnaphthalene and n-alkylphenanthrene surfactants studied exhibit desirable properties that may be of value in some fields such as detergency. To confirm the detergency power of the prepared surfactants, some foam studies were performed.     

Preparation and surface-active properties of telomer-type anionic surfactants from maleic anhydride

Maleic acid alkyl ester and N-alkyl maleamic acid monomers (R_nMa and R_nMaAm; n is alkyl chain length; n=6, 8, 10, 12, 14) were synthesized by the reaction of maleic anhydride with alkyl alcohol or alkylamine. The telomerization of R_nMa or R_nMaAm in the presence of alkanethiol as a chain transfer agent gave telomer-type anionic surfactants (xR_nMa, xR_nMaAm; x is total average number of alkyl chains; x=2.8–3.3) having multialkyl chains and multicarboxylate groups. Their surface-active properties were investigated by several techniques such as surface tension, foaming property, and emulsification power measurements. Critical micelle concentrations (CMC) of xR_nMa were 1/110–1/14 of those of R_nMa with the same alkyl chain length. xR_nMa and xR_nMaAm gave higher efficiencies in lowering the surface tension than R_nMa and R_nMaAm in aqueous solutions. In particular, the surface tension of 3.2R₁₂MaAm was 24.4 mN m⁻¹ at the CMC. Foaming abilities and foam stabilities of xR_nMa and xR_nMaAm were higher than those of R_nMa and R_nMaAm. The addition of 300 ppm of Ca²⁺ to the aqueous solutions rendered the telomers less surface active. Shaking the aqueous solutions of telomers with toluene emulsified them. The highly stable oil-in-water type emulsion was formed by using 3.0R₁₀MaAm and 3.2R₁₂MaAm, and the degree of emulsification was kept at a level of about 80% after 60 min of standing. Thus, telomer-type surfactants showed excellent surface activities that were superior to the corresponding monomers as well as to conventional surfactants. The relationship between alkyl chain length of the telomers and the properties of surface tension, foaming, and emulsification was unclear.     

Solution properties of mixed surfactant system sodium dodecyl sulfate and alkyl polyoxyethylene ether system

The effect of oxyethylene groups in a nonionic surfactant on the solution properties of anionicnonionic systems is described; these systems are sodium dodecyl sulfate (SDS)—hexadecyl polyoxyethylene ethers (C₁₆POE_n, where n=10, 20, 30 and 40). The degree of ionic dissociation of the mixed micelles decreases with increasing numbers of oxyethylene groups in the nonionic surfactant. As polyoxyethylene chain lengths increase, the electrical conductivities of the mixed surfactant solutions decrease, in spite of the decrease in activation energy for conduction. The radius of the mixed micelle with the electric double layer is larger for a nonionic surfactant having a shorter polyoxyethylene chain length than for one having a long polyoxyethylene chain. This may be attributed to the fact that the mixed micelle is formed more easily by a nonionic surfactant with a shorter polyoxyethylene chain length than by one with a longer chain.     

Preparation and surface active properties of terminal amide type of alcohol ethoxylates

Three kinds of title amide compounds with different terminal structures (N-unsubstituted amide, N,N-dimethylamide and acylmorpholine) were prepared from alkyl tetra(oxyethylene) monoethers (alkyl: decyl or dodecyl). The cloud points of the N,N-dimethylamides and acylmorpholines were higher than the other corresponding alcohol ethoxylate derivatives previously developed by us, and all these amides inclusive of N-unsubstituted amides had sufficient hydrophilicity. Surface active properties (CMC, γ_CMC and foaming properties) of these amides in pure water and in hard water (1000 ppm of total hardness as CaCO₃) were almost the same and considered excellent as nonionic surfactants. Furthermore, they showed good lime-soap dispersing ability.     

Solubilization behavior ofn-octane andn-octanol in polyoxyethylated nonionic micelles

The solubilization ofn-octane andn-octanol in nonionic micelles was investigated by means of various techniques including solubilization, fluorescence and dynamic light-scattering measurements. With respect to the effect of oxyethylene chainlength of the surfactants, different solubilization behavior was observed betweenn-octane andn-octanoli.e., the solubilization ofn-octane decreases with an increase in oxyethylene chainlength, while that ofn-octanol increases. This solubilization behavior is explained from the standpoint of the volume of hydrophobic and hydrophilic regions in a micelle.     

Surface active hydroxamic acids. II. Comparison of surface properties of hydroxamic acids with ketones and methyl esters with similar hydrophilic and lipophilic structure

Some surface properties of hydroxamic acids, ketones and methyl esters, which all contained long-chain alkyl[tetra-(oxyethylene)] group, were measured and compared to clarify the influence of the terminal functional group on surface properties. From the results of cloud point (T _cp ), CMC, γ _CMC , adsorption area per molecule at the surface (A) and foaming properties, it was proved that hydroxamic acids had better hydrophilicity and showed better surface properties than the corresponding ketones, methyl esters or typical monodisperse nonionic surfactants.     

无患子皂苷及其复配体系的泡沫性能研究

测定了无患子皂苷的表面活性特征参数，包括HI。B值、浊点、酸值、皂化值、临界胶柬浓度（CMC）、表面张力值（γcmc）等。研究了无患子皂苷与阴离子、非离子和两性表面活性剂复配后的起泡和稳泡结果．从微观结构上分析了复配体系，为无患子皂苷在洗涤剂配方中的应用提供了理论依据。     

Synergistic Effect of Mixed Surfactant Systems on Foam Behavior and Surface Tension

Foam and surface tension behaviors of different ionic/nonionic surfactant solutions along with their different combinations have been investigated. Among different surfactants, sodium dodecyl sulfate showed the highest foamability over other surfactants. Mixed surfactant systems were always found to have higher foamability than the individual surfactant. It was also noticeable that nonionic surfactants show good foamability when they combine with anionic and cationic surfactants. In the case of mixed surfactant systems, nonionic/cationic surfactant mixtures showed lower surface tension than nonionic/anionic surfactant mixture due to a synergistic effect.     

Synthesis of an Alkyl Polyoxyethylene Ether Sulfonate Surfactant and Its Application in Surfactant Flooding

Surfactant flooding as a potential enhanced oil‐recovery technology in a high‐temperature and high‐salinity oil reservoir after water flooding has attracted extensive attention. In this study, the synthesis of an alkyl alcohol polyoxyethylene ether sulfonate surfactant (C₁₂EO₇S) with dodecyl alcohol polyoxyethylene ether and sodium 2‐chloroethanesulfonate monohydrate, and its adaptability in surfactant flooding were investigated. The fundamental parameters of C₁₂EO₇S were obtained via surface tension measurement. And the ability to reduce oil–water interfacial tension (IFT), wettability alteration, emulsification, and adsorption was determined. The results illustrated that IFT could be reduced to 10^?3 mN m^?1 at high temperature and high salinity without additional additives, and C₁₂EO₇S exhibited benign wettability alternate ability, and emulsifying ability. Furthermore, the oil‐displacement experiments showed that C₁₂EO₇S solution could remarkably enhance oil recovery by 16.19% without adding any additives.     

Activity and stability ofPenicillium cyclopium lipase in surfactant and detergent solutions

Activity and stability of an alkaline lipase fromPenicillium cyclopium var.album (PG 37) were studied in surfactant and detergent solutions. Three anionic surfactants [Na salts of C₁₂SO₄ ^? (sodium dodecyl sulfate), C₁₂ØSO₃/^? (linear alkyl benzene sulfonate), and C₁₁COO^? (laurate)] and four homologous series of nonionic surfactants of C_12–15 polyoxethylenated fatty alcohols (AEO₃, AEO₅, AEO₇, and AEO₉) were evaluated. At a concentration range of 3.2–40 μM, sodium dodecyl sulfate and laurate stimulated the activity of PG 37 lipase. At concentrations greater than 5.6 μM, linear alkylbenzene sulfonate inhibited PG 37 lipase activity. Nonionic surfactants, AEO₅ and AEO₇, in the concentration range of 0.25–20 mM, enhanced and stabilized the activity of PG 37 lipase. The presence of PG 37 lipase in detergent formulaton improved detergency ～20%. The mechanism of inhibition of the lipolytic activity of PG 37 lipase is proposed to be partly due to the formation of inactive (BR)_n-E complex between the hydrophobic moiety of the surfactants and the surface of the lipase. Conversely, formation of a soluble (RB)_n-E complex between the hydrophilic group of the surfactant and lipase may account for the increased lipolytic activity of PG 37 lipase.