Tuning the polydispersity of alcohol ethoxylates for enhanced oily soil removal

Commercially available alkyl alcohol ethoxylates have a broad distribution of ethylene oxide (EO) units and also a somewhat narrower distribution of alkyl chain length. Generally, the purer the surfactant sample (narrower distribution), the better is its detergency performance, and detergency peaks at the phase inversion temperature (PIT) for a given oil. However, in real detergency processes this may not hold true since soils are typically mixtures of several oily components, and temperature variations are significant. Therefore, if a polydispersity index (PDI) of ethoxylates is defined as the ratio of weight average EO moles to number average EO moles in the sample, then it is conceivable that an optimal PDI might be obtained. We compared the detergency of hexadecane for pentaethylene glycol monododecyl alcohol (C₁₂EO₅) samples in a broad PDI range, using an oil-soluble dye. While detergency at 55°C (PIT of hexadecane with C₁₂EO₅) decreases monotonically with increasing creasing PDI, average detergency over a 20°C temperature range around the PIT tends to show a maximum at PDI of ca. 1.1 (narrow-range ethoxylate). Similarly, for a mixture of undecane/hexadecane/tetracosane (30∶50∶20 w/w/w) for which the average PIT is approximately the same as that of hexadecane detergency at 55°C shows a maximum as a function of PDI at a value of ∼1.37 (broad-range ethoxylate). All detergency results are in general agreement with the reverse trends in oil/water interfacial tension and suggest that, having decided the optimal EO moles for a given application based on PIT, one can further improve the performance of alcohol ethoxylates in real detergency processes by tuning their polydispersity.     

Measuring detergency of oily soils in the vicinity of phase inversion temperatures of commercial nonionic surfactants using an oil-soluble dye

We have used a simple technique to measure the detergency of model oily soil from 63∶35 blended polyester/cotton fabrics using solutions of commercial linear lauryl alcohol ethoxylates in the vicinity of their phase inversion temperatures (PIT). The method involves incorporation of an oil-soluble dye in the oily soil, and measurement of reflectance at an appropriate wavelength directly on the fabric before and after wash. This technique was validated for our systems, and it provides an additional visual cue for the efficiency of soil removal. Hexadecane, which represents the linear hydrocarbon part of sebum (typical soil encountered in detergency) and has been widely studied in the literature, was used as the model oily soil. Maximal detergency occurs as a function of washing temperature at approximately 35, 62, and 80°C for ethoxylates with four, five, and six moles of ethylene oxide (C₁₂EO₄, C₁₂EO₅, and C₁₂EO₆), respectively. The oil/water interfacial tension, measured using the spinning drop method, exhibits corresponding minima and complements the detergency results. Addition of sodium carbonate, a salting-out electrolyte, decreases the optimal detergency temperature (ODT) of C₁₂EO₅, shifting its behavior toward C₁₂FO₄ whereas addition of anionic surfactant increases the ODT of C₁₂FO₅, mimicking the behavior of a higher ethoxylate.     

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.     

Water solubilization in microemulsions containing amines as cosurfactant

Water-in-oil microemulsions were produced by mixing different combinations of the cationic surfactants cetyltrimethylammonium bromide and cetylpyridinium chloride,n-alkanes (C₅–C₇) and benzene as oils,n-alkylamines (C₆ and C₈) and cyclohexylamine as cosurfactants with water. The influence of chainlength of the alkanes and amines on water solubilization behavior of these systems has been investigated. The solubilization of water in a particular microemulsion is governed by the partitioning of amines among oil, water and interfacial phases, depending on the chainlength and nature of oil and amine, and their interaction with the surfactant. The molar ratio of amine to surfactant at the droplet interface increased with the length of the oil chain. The free energy changes accompanying cosurfactant adsorption at the interface have also been computed.     

Effect of Surfactant Systems,Alcohol Types,and Salinity on Cold-Water Detergency of Triacylglycerol Semisolid Soil. Part II

Our prior work found that detergency of coconut oil was relatively poor using C_14-15-8PO-SO₄Na alone but showed promising improvement with the presence of linear intermediate-chain alcohols (C7–C9 alcohols) in the surfactant formulation. The maximum detergency exceeded 90% removal using 0.1 w/v% C_14-15-8PO-SO₄Na/0.2 w/v% 1-octanol/4 w/v% NaCl (final optimized surfactant system) at 10 °C. The current work thus seeks to further investigate surfactant formulations capable of providing improved detergency performance. Different 50% linear anionic extended surfactant structures (LC_14-15-8PO-SO₄Na, LC_14-15-8PO-3EO-SO₄Na, and LC_14-15-8PO-7EO-SO₄Na) were compared with the branched C_14-15-8PO-SO₄Na previously studied. Detergency of coconut oil using C_14-15-8PO-SO₄Na at 8 w/v% NaCl (S*) still performed more effectively than these new surfactant systems. The addition of octanol as a detergency additive was further studied, and it showed that S* reduced from 8 w/v% NaCl to 4 w/v% NaCl for 1-octanol and to 2 w/v% NaCl for 2-octanol and 2-ethyl-hexanol in the C_14-15-8PO-SO₄Na surfactant formulation. Coconut oil removal significantly improved detergency from roughly 49% for no alcohol with 8 w/v% NaCl, to 83% for 2-ethyl-hexanol with 2 w/v% NaCl, to 95% for 1-octanol with 4 w/v% NaCl, and to 98% for 2-octanol with 2 w/v% NaCl. Further studies on octanol concentration showed that decreasing 1-octanol from 1.2% (90 mM) to 0.2% (15.3 mM) and 2-octanol from 1.2% (90 mM) to 0.5% (38.5 mM) still maintained detergency over 90% removal. In this work, cold-water detergency was found to correlate with low interfacial tension above the melting point, improved wetting of the semisolid soil, and oil solubilization in surfactant micelles.     

Cold Water Detergency of Triacylglycerol Semisolid Soils: The Effect of Salinity,Alcohol Type,and Surfactant Systems

Cold water detergency of triacylglycerol semisolid soils is much more challenging than liquid vegetable oils due to poorer interaction between surfactants and semisolid soil. This research seeks to improve the removal efficiency of semisolid soils below their melting points using surfactant-based formulations containing different alcohol additives. To this end, cold water detergency of solid coconut oil and solid palm kernel oil was investigated in various surfactant/alcohol systems, including single anionic extended surfactants, single nonionic alcohol ethoxylate surfactants, and a mixture of anionic surfactants. A series of alcohols (2-butanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol) were added to the surfactant formulations to investigate cold water detergency improvement. While cold water detergency using surfactants alone was poor, it was considerably improved when optimum salinity (S*) and 1-heptanol, 1-octanol, or 1-nonanol were introduced to the studied surfactant formulations. The maximum detergency of solid coconut oil exceeded 90% removal in the 0.1 w/v% C_14-15-8PO-SO₄Na/0.2 w/v% 1-octanol/4 w/v% NaCl system (a final optimized surfactant system) at a washing temperature of 10°C versus 22.9 ± 2.2% in the surfactant alone (not at optimum salinity and no additive). Further analysis showed that improved cold water detergency using surfactant/intermediate-chain alcohols/NaCl could be correlated with high wettability (low contact angle) as well as favorable surfactant system-soil interaction as observed by lower interfacial tension values. In contrast, the improved cold water detergency was observed to be independent of dispersion stability. This work thus demonstrates that surfactant system design, including additives, can improve cold water detergency of semisolid soils and should be further explored in future research.     

Glycerylbisether sulfates. II: Performance properties

Traditional structure vs. performance relationships have been thoroughly investigated for alcohol ether sulfates (AES) wherein hydrophobe chainlength and degree of ethoxylation served as variables for structure variance. Therefore, a series of molecules, 1,3-bis-(alkylethylenoxy)-propane-2-yl sodium sulfates or glycerylbisether sulfates (GBES), analogous to AES but with a centrally located hydrophile structure, was synthesized and evaluated for its cloth detergency, foaming and wetting properties. Performance test results are presented as response surfaces in the two variables mentioned in addition to comparisons to common surfactants. The centrally located hydrophile structures exhibited varying surfactant and performance properties, with increasing detergency performance shown by higher-molecular weight GBES molecules: Optimum foaming and wetting performance was produced by a range of structures roughly given by C_nEO_n−6 for n=6–8.     

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.     

Importance of micellar relaxation time on detergent properties

As we enter the new millennium, manufacturers of laundry detergents would like to provide new products for the twenty-first century. With the goal of achieving new and better performance characteristics, design strategies for research and development should be defined. This paper highlights the importance of micellar relaxation kinetics in processes involved in detergency. Earlier Shah and coworkers showed that the stability of sodium dodecyl sulfate (SDS) micelles plays an important role in various technological processes. The slow relaxation time (τ₂) of SDS micelles, as measured by the pressure-jump technique, was in the range of 10⁻⁴ to 10¹ s, depending on the surfactant concentration. A maximal relaxation time and thus a maximal micellar stability was found at 200 mM SDS (5 s), corresponding to the least-foaming, largest bubble size, longest wetting time of textile, largest emulsion droplet size, and the most rapid solubilization of oil. These results are explained in terms of the flux of surfactant monomers from the bulk to the interface, which determines the dynamic surface tension. More stable micelles lead to less monomer flux and hence to a higher dynamic surface tension. The relaxation time for nonionic surfactants (as measured by the stopped-flow technique) was much longer than for ionic surfactants because of the absence of ionic repulsion between the head groups. The τ₂ was related to dynamic surface-tension experiments. Stability of SDS micelles can be greatly enhanced by the addition of long-chain alcohols or cationic surfactants. In summary, relaxation time data of surfactant solutions enable us to predict the performance of a given surfactant solution. Moreover, results suggest that one can design appropriate micelles with specific stability, or τ₂, by controlling surfactant structure, concentration, and physicochemical conditions, as well as by mixing anionic/cationic or ionic/nonionic surfactants for a desired technological application, e.g., detergency.     

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.     

Solubilization of selected polycyclic aromatic compounds by nonionic surfactants

Solubilization of selected polycyclic aromatic compounds (PAC) by biodegradable nonionic surfactants, Tergitol 15-S-X (X=7 or 9) and Neodol 25–7, was investigated and correlated with micellar properties of these surfactants. These PAC include dibenzofuran, phenanthrene, acenaphthene, fluoranthene, and 9-chloroanthracene. Tergitol surfactants are mixtures of secondary ethoxylated alcohols, and Neodol 25–7 is a mixture of similar species but has the alcohol group in the primary position. These surfactants have the same chain length of hydrophobic tails and similar numbers of ethylene oxides. The results show that the Neodol surfactant yields micelles having larger hydrophobic core volume and renders a higher solubilization capacity for the PAC solubilizates in comparison with Tergitol surfactants. In general, aggregation numbers and micellar sizes both increase at elevated temperatures still below the cloud point. The micellewater partition coefficients of these PAC by the nonionic surfactants were well correlated to their octanol-water partition coefficients. Moreover, an estimated log K _ow value of 9-chloanthracene is 4.78.     

Synthesis and Characterization of Novel Surfactants based on 2-Hydroxy-4-(Methylthio)Butanoic Acid Part 3: Microemulsions from Nonionic Sulfoxide Ester Surfactants

In this work, ester sulfoxide (ESO) surfactants based on 2-hydroxy-4-(methylthio) butyric acid are shown to have temperature-sensitive microemulsion phase behaviors. Both C10 (C₁₀ESO) and C12 (C₁₂ESO) surfactants studied contained one sulfoxide unit in the structure. Phase inversion temperatures (PIT) and interfacial tensions (IFT) between water-rich and oil-rich phases have been measured for ternary systems of water, oil, and sulfoxide surfactants. Hydrophilic–lipophilic deviation (HLD) parameters of these surfactants were obtained by fitting the experimental data to a semiempirical HLD equation. The characteristic surfactant parameter and temperature sensitivity of C₁₀ESO and C₁₂ESO surfactants were obtained and compared with similar ethoxylated alcohol surfactants. By comparing the characteristic parameters of these surfactants with those of ethoxylated alcohol surfactants, it was shown that one sulfoxide ester moiety is equally hydrophilic as approximately 5 ethylene oxide groups. The temperature sensitivity of the ESO was roughly a factor of four less than ethoxylated surfactants based on the temperature coefficient of the HLD equation.     

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.     

Solubilization of cholesterol in two binary mixed micelles of bile salt and nonionic surfactant

The saturated amounts of solubilized cholesterol (C_ch) in mixed micelles of sodium cholate (NaC) and octaoxy-ethylene glycol monon-decyl ether (C₁₀E₈) and of sodium zyme assay at 25, 29, 33 and 37°C. The C_ch values in both systems increase with the total surfactant concentration. Because the mixed micelles for both systems tend to form C₁₀E₈-rich micelles near the critical micellar concentration (CMC) of the mixed system, the curves of cholesterol solubility approached the C_ch curve for C₁₀E₈ alone near the CMC. The tendency of C_ch to decrease in both systems with increasing mole fractions of bile salts resembled that of the mean aggregation number of micelles. Thermodynamic analyses of cholesterol solubilization showed that the free energy of solubilization, if considered as the transfer of cholesterol from solid state to micellar environment, increased with increasing mole fraction of bile salt. The enthalpy of cholesterol solubilization (ΔH_S→M) decreased with the mole fraction of bile salts and showed break points around the mole fraction of 0.75 for the NaC−C₁₀E₈ system and at 0.60 for the NaDC−C₁₀E₈ system, respectively. These phenomena resemble earlier hydrophobicity data for mixed micelles by fluorescence measurements. Furthermore, C_ch values for the NaDC−C₁₀E₈ system were larger than those for the NaC−C₁₀E₈ system because of the structural differences at the 7α hydroxyl group between NaC and NaDC. This fact was confirmed by thermodynamic calculations.     

Laundry Detergency of Solid Nonparticulate Soil or Waxy Solids: Part II. Effect of the Surfactant Type

In this work, methyl palmitate with a melting point around 30°C was used as a model of waxy soil. Its detergency was evaluated with a hydrophilic surface (cotton) or a hydrophobic surface (polyester) using different surfactants: alcohol ethoxylate (EO9), sodium dodecyl sulfate (SDS), methyl ester sulfonate (MES), methyl ester ethoxylate (MEE), and two extended surfactants (C_12,14-10PO-2EO-SO₄Na and C_12,14-16PO-2EO-SO₄Na). The detergency efficiency at a 0.2 wt.% surfactant and 5 wt.% NaCl gradually increased while redeposition gradually decreased with increasing washing temperature in most studied surfactant solutions; this was observed both above and below the melting point of methyl palmitate on both studied fabrics. If the methyl palmitate was heated above the melting point when deposited on the fabric, it was better able to penetrate into the fabric matrix as compared to deposition below the melting point, resulting in poorer detergency for heated deposition, particularly for washing temperatures lower than the melting point. Among the surfactants studied, the nonionic surfactant (EO9) showed the highest detergency efficiency (73–94%) at any washing temperature especially on the polyester fabric. For washing temperatures below the melting point, detergency performance correlated well with the contact angle of surfactant solution on the solid methyl palmitate surface for all studied surfactants when salinity was varied. In this work, conditions resulting in the highest detergency below the melting point corresponded to the highest detergency above the melting point, suggesting this as a systematic approach to formulating below the melting point of the soil. Charge of particles or fabric was not observed to be important to the detergency mechanism, but steric factors resulting from surfactant adsorption were observed to be important mechanistic factors in waxy solid detergency.     

Effect of Hydrophobicity and Temperature on the Interactions in the Mixed Micelles of Triblock Polymers [(EO76PO29EO76) and (EO19PO69EO19)] with Monomeric and Gemini Surfactants

The interactions in the mixed micelles of two triblock polymers, F68 (EO₇₆PO₂₉EO₇₆) and P123 (EO₁₉PO₆₉EO₁₉), with a series of monomeric (dodecyltrimethyl ammonium bromide, tetradecyltrimethyl ammonium bromide and cetyltrimethyl ammonium bromide) and gemini {dimethylene bis(alkyldimethyl ammonium bromide), m-2-m, where m = 10, 12 and 14} cationic surfactants were studied by surface tension and viscosity measurements in aqueous solutions at different temperatures. The mixed micellar and interfacial properties of the binary mixtures were analyzed using Clint, Rubingh, Rosen and Maeda approaches. Both F68 and P123 show weak interactions with the studied cationic surfactants at 298.15 K which become favorable (synergistic) at higher temperatures. Further, the synergistic interactions are more in mixtures of P123 than F68 at higher temperatures. A comparison of the effects of number of EO and PO blocks in triblock polymers on various physicochemical parameters of the mixed micelles has also been made. The unfavorable enthalpy changes are compensated by favorable entropy changes as a result of the hydrophobic effect. The relative viscosity (η _r) studies show that the size of the micelles formed by pure P123 is smaller than those of F68. The values of η _r for the mixed micelles of F68 show significant variation with chain length of gemini surfactants whereas no such effect is seen in mixtures with P123.     

The mixed surfactant system of linear alkylbenzene sulfonate and alpha olefin sulfonate

Physicochemical and detergency studies on the mixed surfactant system of linear alkylbenzene sulfonate-sodium salt (LABS) and alpha olefin sulfonate-sodium salt (AOS) have been carried out. The binary surfactant system exhibits minima in the surface tension and in the critical micelle concentration when the two surfactants are present in the ratio 80:20, indicating synergism in the mixed monolayer and in mixed micelles at this proportion of the two surfactants. The mixed micelles improve hard-water tolerance of LABS and reduce the loss of LABSvia Ca(LABS)₂ precipitation. Addition of AOS to LABS improves its lime soap dispersion properties. The effect is highly significant when AOS is present at the 20% level in the mixed surfactant system. A synergistic mixture of the two surfactants, when used in phosphate-free, carbonate-built detergent product formulation, exhibits superior detergency, low ash deposit and better stainremoving ability when compared to products containing LABS as the sole active surfactant.     

Optimized Microemulsion Systems for Detergency of Vegetable Oils at Low Surfactant Concentration and Bath Temperature

Triglycerides and vegetable oils are amongst the most difficult oils to remove from fabrics due to their highly hydrophobic nature; this is all the more challenging as cold water detergency is pursued in the interest of energy efficiency. Recently, extended surfactants have produced very encouraging detergency performance at ambient temperature, especially at low surfactant concentration. However, the salinity requirement for extended surfactants was excessive (4–14%) and there is limited research on extended‐surfactant‐based microemulsions for cold water detergency (below 25 °C). Therefore, extended‐surfactant‐based microemulsions are introduced in this study for cold temperature detergency of vegetable oils with promising salinity and surfactant concentration. The overall goal of this study is to explore the optimized microemulsion formulations with low surfactant and salt concentration using extended surfactant for canola oil detergency at both 25 and 10 °C. It was found that microemulsion systems achieved good performances (higher than those of commercial detergents) corresponding to IFT value 0.1–1 mN/m with the surfactant concentration as low as 10 ppm and 4% NaCl at 25 °C, and as low as 250 ppm and 0.1% (1000 ppm) NaCl at 10 °C. In addition, microemulsion systems were investigated with a different salt (CaCl₂, or water hardness, versus NaCl) at 10 °C, demonstrating that 0.025% CaCl₂ (250 ppm) can produce good detergency; this is in the hardness range of natural water. These results provide qualitative guidance for microemulsion formulations of vegetable oil detergency and for future design of energy‐efficient microemulsion systems.     

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.     

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.