Review: Implementing the hydrophilic–lipophilic deviation model when formulating detergents and other surfactant-related applications

When designing surfactant formulations using ionic and nonionic surfactants, the hydrophile lipophile balance (HLB) is a generalized surfactant characterization parameter that has shown to be useful when designing surfactant formulations, in the case of both ionic and nonionic surfactants (Davies' and Griffin's methods). Microemulsion phase behavior studies have been extensively used to optimize surfactant formulations, but these studies can cover a very wide phase space and can often encounter troublesome non-equilibrium issues such as coacervation. Detailed phase behavior studies can be time-consuming and difficult to apply beyond the specific surfactant-oil system studied. The hydrophilic–lipophilic deviation (HLD) provides a method to help expedite surfactant formulation research by reducing the number of phase behavior studies required to optimize a given formulation. Detergency experiments have indicated that there is an optimal range of HLD for a given fabric surface. This appears to apply to other applications, as well, for example, surfactant formulations used in enhanced oil recovery have been optimized using the HLD method. These studies found that the HLD can reflect total oil recovery, even if the surfactants were derived from different alcohol feedstocks (e.g., HLD of 0 would describe optimum conditions regardless the type of surfactant). Also with additional parameterization, the HLD method can also be applied to non-ideal surfactant mixtures, specifically ionic/nonionic blends. Overall, the HLD framework has shown to be an effective screening tool for a wide range of surfactant-related applications when appropriate experiments, assumptions, and understanding of surfactant and oil interactions are used to generate the HLD parameters.     

Reactive surfactants in heterophase polymerization. XVII. Influence of the surfactant on the mechanical properties and hydration of the films

In the context of a European union‐supported network on “Reactive Surfactants for Heterophase Polymerization,” different polymerizable surfactants (surfmers) have been synthesized and engaged in the emulsion polymerization of styrene, butyl acrylate, and acrylic acid. The thermomechanical properties of films cast from these different latices are reported in this article. The evolution of the mechanical properties with temperature and the effect of water molecules on these properties are studied. We observed that the studied surfactants do not influence the properties of the dry films. However, some differences due to grafting of reactive surfactants appeared when the films were wet. The amount of water uptake is drastically decreased when only reactive surfactants are present in the film. Concerning the mechanical behavior of the wet films, a decrease of the plastic flow stress is observed for all the samples whatever the nature of the surfactant (reactive or conventional). Hence, calorimetric measurements and dynamic mechanical analysis are used to identify the possible mechanisms that induce the change in the mechanical behavior of the latex films. In the case of reactive surfactant grafted to the polymer, the very low value of water uptake is accompanied by a plasticization of the polymer. In contrast, no plasticizing effect is observed in the case of nonreactive surfactant, even if the amount of water is very large. Finally, the tensile behavior of the styrene–butyl acrylate copolymer versus temperature is analyzed in the frame of the quasi point defects (qpd) model. Both rubber elasticity and chain orientation effects are taken into account to describe the behavior laws at large extensions (i.e., ? ≈ 1.2). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1686–1700, 2002; DOI 10.1002/app.10548     

Effect of surfactant systems on the water sensitivity of latex films

The effects of three different types of surfactant systems (ionic, polymeric, and electrosteric stabilizers) on the water sensitivity of poly(butyl acrylate‐co‐methyl methacrylate) latex films was examined. The water sensitivity was found to be strongly dependent on the surfactant system used in their preparation. A number of factors, such as the surfactant mobility and crystallinity and surfactant/polymer polarity appeared to affect the water uptake of the films. Highly mobile and crystallizable surfactants yielded high water sensitivity for films containing ionic surfactants, whereas the surfactant polarity had a greater effect on latices stabilized by polymeric surfactants, with the more hydrophilic systems providing greater water uptake. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1813–1823, 2004     

Propagation of Surfactant-Dispersed Multiwalled Carbon Nanotubes in Porous Media

Understanding the transport of carbon nanotubes in porous media is essential to their applications in subsurface reservoirs, e.g., delivering catalysts or chemicals to targeted formations. In this study, a series of laboratory experiments are conducted to explore the transport of surfactant-dispersed multiwalled nanotubes (MWNT) in different porous media in flow-through columns at elevated electrolyte levels. Noncovalent bonding of ethoxylated alcohols adsorbed on the MWNT surface provides them with outstanding dispersion stability and excellent transport properties in a crushed-limestone sand pack. Superior transport performance in silica sand is obtained with binary nonionic–anionic surfactant formulations, which provide both steric repulsion and electrostatic repulsion between nanoparticle–nanoparticle and nanoparticle–sand surface. The mobility of MWNT suspensions are further investigated in the exposure to multiphase flow, e.g., with residual oil present, or coinjected with air into the sand pack. Coinjecting surfactant-dispersed MWNT suspensions with air (i.e., MWNT-stabilized foams) has hardly any impact on their propagation; retention in the sand pack remains quite low. With the presence of oil in the sand pack, the transport of MWNT suspensions is highly dependent on the type of surfactants used as the dispersant. For surfactants that achieved modest interfacial tension (IFT) reduction, the injected MWNT suspension bypasses the oil phase, and little impact on retention is observed. When the dispersant surfactant is also adjusted for an ultralow IFT condition, greater MWNT retention in the porous medium is observed because surfactants detach from the MWNT surface and aggressively partition to the oil/water interface, allowing the MWNT to flocculate and become deposited in the porous medium.     

Study of the efficiency of technical grade nonionic surfactants

Parameters concerning the microemulsion phase behavior of nonionic surfactants of the alkyl polyglycol ether type have extensively been investigated in the last years. By studying these, essential parameters for future applications can be determined. Especially in the field of enhanced oil recovery, lubricants, and cosmetic applications these parameters are of special interest. In this work, the influence of technical grade nonionic surfactants on the phase behavior and the resulting surfactant efficiency has been studied. For this, the alkyl chain length, the degree, type, and order of alkoxylation of the surfactant have been varied. The investigation of these parameters has been conducted by measuring the phase behavior via the Kahlweit fish diagram. It has been found that varying the C-chain length has a great impact on the efficiency, whereas the influence of the ethoxylation degree is minor. By the introduction of propylene oxide, the efficiency has been improved significantly. Additionally, it is important to have the right order of alkoxylation. If the fatty alcohol is first ethoxylated and afterwards propoxylated the efficiency is significantly decreased.     

ADSORPTION OF ETHOXYLATED NONIONIC SURFACTANTS FROM SILOXANE-BASED SOLVENT AND AQUEOUS SYSTEMS: USE OF QCM AND MODEL POLYMERIC SURFACES

Adsorption behavior was quantified with pure ethoxylated nonionic surfactants onto different polymeric surfaces (hydrophilic cotton and hydrophobic polyester) and model hydrophilic gold surface. The polymer materials used for the study were characterized using SEM. The role of ethylene oxide group variation in surfactant-polymer interaction was established using pure surfactant with the same alkyl chain length but varying ethoxylate chain lengths. It was observed that surfactant with more ethylene oxide groups per molecule, being more hydrophilic, interacts favorably with cotton in the hydrophobic siloxane solvent environment. The adsorption of the pure surfactants on model gold surface from hydrophobic solvent and water was also established using the quartz crystal microbalance with dissipation monitoring (QCM-D) system. Effect of ethylene oxide chain length and surfactant concentration on the extent of adsorption was quantified. At the gold-water interface, the plateau adsorption for C₁₂ E₃ (15.9 × 10^?6 mole/m²) is about four times higher than for C₁₂E₈. An opposite trend was observed for adsorption of the surfactants on gold in the hydrophobic D5 environment. Information about thickness, adsorption and desorption kinetics, and structure of adsorbed layer was obtained from the QCM-D frequency-dissipation data. The study is an important contribution towards fundamental understanding of applications involving the use of ethoxylated nonionic surfactants.     

Photopolymerization kinetics of poly(acrylate)-clay composites using polymerizable surfactants

Photopolymerization kinetics of polymer-clay nanocomposite systems utilizing polymerizable quaternary ammonium surfactants as dispersants were systematically investigated to determine the effects of surfactant type and clay morphology on polymerization behavior. For these studies, either polymerizable surfactants were mixed into a clay-monomer system or the surfactants were ionically anchored to clay surfaces and added to the monomer for in situ photopolymerization. Higher photopolymerization rates are observed with increasing polymerizable surfactant concentration, while no significant change or decreases in polymerization rate occur with incorporation of non-polymerizable surfactants. The higher rates observed for polymerizable surfactant systems are due to lower apparent termination rate parameters stemming from immobilization of the surfactants. For clay that is modified with ionically bonded quaternary ammonium surfactants, polymerization rates decrease in both polymerizable and non-polymerizable organoclay systems with increasing concentration, but this decrease is much smaller when polymerizable organoclays are utilized. For the same organoclay concentration, higher polymerization rates and double bond conversions result with increasing polymerizable surfactant concentration via cation exchange. Significant increases in polymerization rate also occur with increasing degree of clay exfoliation.     

Detergency and foam studies on linear alkylbenzene sulfonate and secondary alkyl sulfonate

Among anionic surfactants used in detergent products, the sodium salt of linear alkylbenzene sulfonate (NaLAS) is the only surfactant belonging to the aromatic class; the others are aliphatic, e.g., the sodium salt of secondary alkyl sulfonate (NaSAS). We observed earlier that certain conformational changes taking place in aromatic anionic surfactants (NaLAS) upon micellization can be brought about in aliphatic anionic surfactants (NaSAS) by addition of phenol. In this paper we examined how conformational changes at the molecular level translated into macroscopic properties such as foam and detergency. We performed foam and detergency measurements on NaLAS, NaSAS, and NaSAS/phenol systems. Foam behavior of these systems is shown to be dependent only upon calcium ion sensitivities of the surfactants whereas the detergency results have a dependence on conformational changes at the molecular level.     

Synergism and Performance for Systems Containing Binary Mixtures of Anionic/Cationic Surfactants for Enhanced Oil Recovery

The surfactant structure–performance relationship and application properties in enhanced oil recovery (EOR) for binary mixtures of anionic and cationic surfactants are presented and discussed. A polyoxyethylene ether carboxylate anionic surfactant was blended with a quaternary ammonium chloride cationic surfactant and tested for a high-temperature, low-salinity, and high-hardness condition as found in an oil reservoir. These mixtures were tailored by phase behavior tests to form optimal microemulsions with normal octane (n-C8) and crude oil having an API gravity of 48.05°. The ethoxy number of the polyoxyethylene carboxylate anionic surfactant and the chain length of the cationic surfactant were tuned to find an optimal surfactant blend. Interfacial tensions with n-C8 and with crude oil were measured. Synergism between anionic and cationic surfactants was indicated by surface tension measurement, CMC determination, calculation of surface excess concentrations and area per molecule of individual surfactants and their mixtures. Molecular interactions of anionic and cationic surfactants in mixed monolayers and aggregates were calculated by using regular solution theory to find molecular interaction parameters β ^σ and β ^M . Morphologies of surfactant solutions were studied by cryogenic TEM. The use of binary mixtures of anionic/cationic surfactants significantly broadens the scope of application for conventional chemical EOR methods.     

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.     

Influence of Surfactants on the Rheology and Stability of Crystallizing Fatty Acid Pastes

Complex fluids containing crystallizing fatty acids are important for consumer care products. The key features of these materials are their ability to support their weight under gravity due to the formation of a fatty acid crystal network, and to yield or flow beyond a critical applied strain. In model formulations comprised of two synthetic surfactants and a fatty acid in water, we have shown that the fatty acid crystal network consists of crystal aggregates linked by a non-crystallized mixed fatty acid—surfactant mesophase. We hypothesize that this mixed surfactant—fatty acid mesophase is critical for the macroscopic stability of the formulations. Rheological measurements combined with differential scanning calorimetry (DSC), X-ray scattering, and polarized light microscopy (PLM) measurements show the importance of surfactant loading on the overall stability of the formulations by linking morphology to rheology. Macroscopically homogeneous formulations are realized with 7–10 wt% of fatty acid. Increasing the fatty acid content without adding surfactant leads to inhomogeneous, phase separating formulations. Although both stable and unstable formulations show the presence of a surfactant—fatty acid mixed phase, a critical loading of surfactants is found to be necessary to create macroscopically homogenous formulations. We demonstrate how the rheology, microstructure and the macroscopic stability can be tuned by varying the relative amounts of surfactants and fatty acid.     

Salt-Induced Constructions of Gemini-like Surfactants at the Interface and Their Effects on the Interfacial Tension of a Water/Model Oil System

It is an urgent issue to enhance oil recovery for unconventional reservoirs with high salinity. Focused on this topic, salt addition is a powerful tool to motivate the surfactant assembly at the water/oil interface and improve the interfacial activity. We used a cationic surfactant cetyltrimethylammonium bromide (CTAB) and an anionic salt dicarboxylic acid sodium (CnDNa) to construct gemini-like surfactants at the interface and evaluated their ability to reduce the interfacial tension (IFT) between model oil (toluene and n-decane, v:v = 1:1) and water. Interestingly, the fabrication of a (CTAB)₂/C4DNa gemini-like surfactant was hardly achieved at the fresh water/model oil interface, but accomplished at the brine/model oil interface. At a high NaCl concentration (100,000 mg L⁻¹), the IFT value is reduced to 10⁻³ mN m⁻¹ order of magnitude, which is generally desired in practical applications. The control experiments displacing the surfactant type and the spacer length further confirmed the NaCl effects on the interfacial assembly.     

Synthesis and characterization of polymerizable epoxy resin surfactants

Polymerizable epoxy resin (PER) surfactants have been prepared from the reaction of bisphenol A epoxy resin with acrylic acid, followed by the reaction with polyethylene glycol (PEG) with different molecular weights. The reaction procedures were monitored by chemical titrations, infrared spectroscopy, and NMR. The products show typical surface‐active properties as but much higher water solubility than nonpolymerizable nonionic surfactant OP‐10. With the increase of PEG's molecular weight, the HLB value, the water solubility, and the critical micellar concentration (CMC) of the PER surfactants, the cloud point of the PER surfactant solutions, as well as the solubilization capability of the PER surfactants to organic compounds increase under the experimental conditions. The copolymerization under UV radiation indicated that about 75–80 wt % of PER surfactants participated in the copolymerization with epoxy diacrylate (EdA), except for the PER surfactant with the lowest PEG molecular weight of 1 k. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42598.     

Surface tension,adsorption, and wetting behaviors of natural surfactants on a PTFE surface

The adsorption kinetics and wetting behaviors of three plant‐based natural surfactants (Reetha, Shikakai, and Acacia) on the polytetrafluoroethylene (PTFE) surface are reported in this study. Adsorption studies of these surfactants on PTFE surface show the equilibrium adsorption time is approximately 15 min, and Langmuir‐type isotherm fits well for all three surfactants. The contact angle measurements show that the value achieved by Reetha and Acacia solutions are close (～109°), but that is low in the case of Shikakai (98.13°). Although, comparing the adsorption densities of the surfactants at PTFE–water and air–water interfaces, it has been found that adsorption densities at the PTFE–water interface are low for all three surfactants than that of air–water interface. The alcohol–Shikakai mixed solutions show nonideal behavior of surface tension reduction through a strong interaction between alcohol and Shikakai molecules, which in turn, show lower surface tension and contact angle values than that of ideal. © 2014 American Institute of Chemical Engineers AIChE J, 61: 655–663, 2015     

Effect of serum components on styrene/butyl acrylate latex film formation: An in situ examination by ultramicroscopy

Film formation by a surfactant‐stabilized, peroxide‐initiated styrene/butyl acrylate latex was followed in situ by ultramicroscopy. The effects of latex serum components on film formation were observed first by the subjection of the latex to extensive dialysis and then by the separate addition of salt and surfactants. Domains of different particle concentrations were observed in the latex dispersion during liquid evaporation, and their positions were related to those of defects in the dry film. Films obtained with the dialyzed latex showed macroscopic defects, which were not seen in the as‐prepared latex. Partially reconstituted latex (dialyzed, with the later addition of salt but not surfactant) behaved like the as‐prepared latex. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 159–167, 2003     

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.     

Application of magnetic nanoparticles as demulsifiers for surfactant-enhanced oil recovery

Nonionic surfactants are increasingly being applied in oil recovery processes due to their stability and low adsorption onto mineral surfaces. However, these surfactants lead to the production of emulsified oil that is extremely stable and difficult to separate by conventional methods. This research characterizes the stability of crude oil mixed with a nonionic surfactant, L24–22, in a brine solution. When subjected to gravity separation, a middle oil-rich and bottom water-rich emulsion are generated for various water–oil ratios. Thermal treatments can effectively break oil-rich emulsions, but the bottom water layer remains contaminated with micron-sized crude oil droplets. A magnetic nanoparticle treatment is shown to demulsify the crude oil emulsions, dropping the total organic carbon (TOC) in the water layer from 1470 to 30 ppm.     

Reactive Surfactants for Achieving Open-Cell PolyHIPE Foams from Pickering Emulsions

PolyHIPEs, highly porous polymers synthesized within high internal phase emulsions (HIPEs), emulsions with over 74% internal phase, are of interest for applications such as absorbents, reaction supports, and tissue engineering scaffolds. Typically, the surfactant contents for HIPE stabilization are relatively high, ranging from 20 to 30 wt% of the external phase, with the monomers usually being the remainder. One drawback of using surfactants for these applications is the potential for leachables, necessitating intensive purification processes for their removal. Pickering HIPEs, HIPEs stabilized using amphiphilic solid nanoparticles that spontaneously migrate to the oil–water interface, can be used as an alternative HIPE stabilization strategy. Although nanoparticles can add surface functionality advantageous for the application, polyHIPEs from Pickering HIPEs often lack the interconnecting holes needed for the high permeability required for such applications. This work describes a successful approach for designing an HIPE stabilization system that is based on a combination of nanoparticles and reactive surfactants and that generates the desired surface functionality, an interconnected porous structure, and a low leachable content. Such an approach can extend the applicative utility of such polyHIPEs by circumventing the need for extensive purification.     

Effect of Self-Assemblies on the Dynamics of the Briggs–Rauscher Reaction

The study involves the dynamic evolution of the Briggs–Rauscher (BR) reaction in the presence of various surfactants—SDS (sodium dodecyl sulphate) as anionic, CTAB (cetyl trimethylammonium bromide) as cationic and TritonX‐100 [4‐(1,1,3,3‐(tetramethylbutyl) phenyl polyethylene glycol] as a neutral one in single as well as mixed mode conditions (SDS + TX‐100 and CTAB + TX‐100). The reaction has been monitored potentiometrically at 30 °C under CSTR conditions. These surfactants affect the reaction dynamics to an extent which depends on the nature and concentration of the surfactant and the formation of their self‐assemblies. The experimental findings indicate that the oscillatory behavior of the BR reaction in the presence of surfactants is due to the efficacy of organized surfactant assemblies to selectively distribute the key species involved in the reaction, and their interaction with the counter ions in cases of ionic micelles. The study reveals that the evolution of oscillatory behavior is a characteristic feature of the surfactant.     

Surfactant Enhanced Oil Recovery in a High Temperature and High Salinity Carbonate Reservoir

The goal of this work was to find an effective surfactant system for enhanced oil recovery after water injection substituting for oil at a vuggy fractured reservoir with a high temperature and high salinity (220,000 mg/L). Four types of surfactants with concentrations (less than 0.2 %) were screened. Washing oil experiments were conducted in Amott cells. A surfactant system was established by mixing a surfactant with best ultimate recovery and one with best recovery rate. The optimized surfactant system could recover 50 % of remaining oil. To study the mechanism of enhanced oil recovery after water injection substituting oil, interfacial tension (IFT) and contact angle were measured. Experimental results showed that surfactants with good washing ability had low IFT, but surfactants with low IFT may not have a good washing ability. IFT had no obvious relationship with the increased oil recovery or washing ability. The optimized system could not alter carbonate to decrease the oil‐wetting capability. Though octadecyl trimethyl ammonium chloride had a good ability wet the carbonate with water, it could not recover much oil. Therefore, except for interfacial tension and wettability alteration, there must be other parameters dominating oil recovery after water injection substituting for oil.