A review of shampoo surfactant technology: consumer benefits, raw materials and recent developments

Comprehensive rheological analysis of structurally related acetan-like heteroexopolysaccharides from two Kozakia baliensis strains in surfactants and galactomannan blends

Natural biopolymers become increasingly attractive as bio-based alternatives to petrol-based rheological modifiers, especially in personal care applications. However, many polysaccharides exhibit undesired properties in cosmetic applications such as limited viscosifying characteristics, unpleasant sensory properties, or incompatibility with certain formulation compounds. Here, a comprehensive rheological analysis of non-decorated acetan-like heteroexopolysaccharides derived from two Kozakia baliensis strains was performed in selected surfactant formulations. The results were compared to native xanthan gum and a genetically engineered xanthan variant, Xan∆gumFGL, which lacks any acetyl- and pyruvyl moieties and whose rheological properties are unaffected by saline environments. All four polysaccharides displayed a highly similar rheological performance in the non-ionic surfactant lauryl glucoside, while the rheological properties differed in amphoteric and anionic surfactants cocamidopropyl betaine and sodium laureth sulfate due to minor changes in side chain composition. Polysaccharide precipitation was observed in the presence of the cationic surfactant. Nevertheless, the native heteroexopolysaccharide derived from K. baliensis LMG 27018 shows significant potential as a salt-independent rheological modifier compared to the genetically engineered Xan∆gumFGL variant. In addition, blends of heteroexopolysaccharides from K. baliensis and several galactomannans displayed synergistic effects which were comparable to native xanthan gum-galactomannan blends. This study shows that heteroexopolysaccharides of K. baliensis are capable of further extending the portfolio of bio-based rheological modifiers.

Classification of surfactants and admixtures for producing stable aqueous foam

Surfactants and foam have captured the interest of researchers worldwide due to their unique behavior of surface activity, the dynamic nature of foam formation, and simultaneous destruction. The present review focuses on the surfactants' classification, surfactant-solvent interaction, foam formation, characteristics, and a range of admixtures to enhance the foam performance. Although surfactants have been researched and developed for decades, recently, their sustainability has been given special attention. One such aspect is the development of green foaming agents from natural and renewable sources and assessing their suitability for different applications. Further, widely researched parameters are the type of surfactant, surfactant concentration, surfactant-solvent interaction, and foam production method on the foamability of a surfactant solution and related foam characteristics, including stability and texture. However, still, there is no rule to predict the best foam. Another vital concern is the non-standardization of foam assessment methods across industries and regions. Recently, research has progressed in identifying suitable admixtures for foam performance enhancement and utilizing them to produce stable foams for application in enhanced oil recovery, drug delivery, and manufacturing of aerated food products and foamed concrete. Although foam stabilization using various admixtures has been recognized well in the literature, the underlying mechanism requires further research. The interaction of surfactant and admixtures in solution is complicated and requires more research.

Influence of surfactant molecular features on tetracycline transport in saturated porous media of varied surface heterogeneities

This study aims to understand how surfactants affect the mobility of tetracycline (TC), an antibiotic, through different aquifer media. Two anionic and cationic surfactants, sodium dodecylbenzene sulfonate (SDBS) and cetyltrimethyl ammonium bromide (CTAB), were used to study their influence on TC mobility through clean sand and humic acid (HA)-coated sand. HA coating inhibits TC mobility due to its strong interaction with TC. Both surfactants promoted TC mobility at pH 7.0 due to competitive deposition, steric effect, and increased hydrophilicity of TC. CTAB had a more substantial effect than SDBS, related to the surfactants' molecular properties. Each surfactant's promotion effects were greater in HA-coated sand than in quartz sand due to differences in surfactant retention. CTAB inhibited TC transport at pH 9.0 due to its significant hydrophobicity effect. Furthermore, in the presence of Ca2+, SDBS enhanced TC transport by forming deposited SDBS-Ca2+-TC complexes. On the other hand, CTAB increased TC mobility due to its inhibition of cation bridging between TC and porous media. The findings highlight surfactants' crucial role in influencing the environmental behaviors of tetracycline antibiotics in varied aquifers.

Boundary Lubrication Performance of Polyelectrolyte-Surfactant Complexes on Biomimetic Surfaces

Aqueous mixtures of oppositely charged polyelectrolytes and surfactants are useful in many industrial applications, such as shampoos and hair conditioners. In this work, we investigate the friction between biomimetic hair surfaces in the presence of adsorbed complexes formed from cationic polyelectrolytes and anionic surfactants in an aqueous solution. We apply nonequilibrium molecular dynamics (NEMD) simulations using the coarse-grained MARTINI model. We first developed new MARTINI parameters for cationic guar gum (CGG), a functionalized, plant-derived polysaccharide. The complexation of CGG and the anionic surfactant sodium dodecyl sulfate (SDS) on virgin and chemically damaged biomimetic hair surfaces was studied using a sequential adsorption approach. We then carried out squeeze-out and sliding NEMD simulations to assess the boundary lubrication performance of the CGG-SDS complex compressed between two hair surfaces. At low pressure, we observe a synergistic friction behavior for the CGG-SDS complex, which gives lower shear stress than either pure CGG or SDS. Here, friction is dominated by viscous dissipation in an interfacial layer comprising SDS and water. At higher pressures, which are probably beyond those usually experienced during hair manipulation, SDS and water are squeezed out, and friction increases due to interdigitation. The outcomes of this work are expected to be beneficial to fine-tune and screen sustainable hair care formulations to provide low friction and therefore a smooth feel and reduced entanglement.

Transparent silicone-free shampoo containing proteins with strong hair conditioning properties

OBJECTIVE

With the constant upgrading of healthcare concepts, silicone-free hair products have attracted more attention among consumers. In the present study, transparent silicone-free shampoo containing proteins was successfully fabricated by mixing mild non-sulphate surfactants, compound cationic conditioners, natural silicone oil substitutes, protein conditioners, thickeners, and other auxiliary ingredients. The effects of the type of surfactants, hair conditioners and thickeners, the type and content of proteins, and the mass ratio of compound proteins on the hair foaming performance, hair grooming performance, and penetration performance were investigated.

METHODS

The basic formulation framework for transparent silicone-free shampoo was established at first. Then, various hydrolyzed proteins were further added to the basic formulation in the form of single use or compound use to prepare transparent silicone-free shampoo containing different proteins. The morphology of hair samples and penetration of protein in hair were evaluated with a scanning electron microscope and laser confocal fluorescence microscopy, respectively. And the hair grooming performance was also determined by a dynamic combing tester.

RESULTS

The compound proteins of Croquat WKP PE-LQ-WD and Gluadin® Kera-PLM with mass ratios of 1:9 and 1:1 at 2 wt% total protein content added to the silicone-free shampoo brought a higher contact angle and a lower frictional coefficient than commercial silicone-free shampoo without proteins. In addition, the compound proteins also have the dual effect of adsorbing the hair surface and penetrating deep into the interior of the hair.

CONCLUSION

The combination of cationic modified hydrolyzed protein (e.g., Croquat WKP PE-LQ-WD) and hydrolyzed protein with low molecular weight (e.g., Gluadin® Kera-P LM) at an appropriate mass ratio exhibited a strong synergistic effect on hair conditioning properties. It could provide a significant reference for developing silicone-free hair products with more benefits.

Influence of Surfactant Structure on Polydisperse Formulations of Alkyl Ether Sulfates and Alkyl Amidopropyl Betaines

Surfactants provide detergency, foaming, and texture in personal care formulations, yet the micellization of typical industrial primary and cosurfactants is not well understood, particularly in light of the polydisperse nature of commercial surfactants. Synergistic interactions are hypothesized to drive the formation of elongated wormlike self-assemblies in these mixed surfactant systems. Small-angle neutron scattering, rheology, and pendant drop tensiometry are used to examine surface adsorption, viscoelasticity, and self-assembly structure for wormlike micellar formulations comprising cocoamidopropyl betaine, and its two major components laurylamidopropyl betaine and oleylamidopropyl betaine, with sodium alkyl ethoxy sulfates. The tail length of sodium alkyl ethoxy sulfates was related to their ability to form wormlike micelles in electrolyte solutions, indicating that a tail length greater than 10 carbons is required to form wormlike micelles in NaCl solutions, with the decyl homologue unable to form elongated micelles and maintaining a low viscosity even at 20 wt % surfactant loading with 4 wt % NaCl present. For these systems, the incorporation of a disperse ethoxylate linker does not enable shorter chain surfactants to elongate into wormlike micelles for single-component systems; however, it could increase the interactions between surfactants in mixed surfactant systems. For synergy in surfactant mixing, the nonideal regular solution theory is used to study the sulfate/betaine mixtures. Tail mismatch appears to drive lower critical micelle concentrations, although tail matching improves synergy with larger relative reductions in critical micelle concentrations and greater micelle elongation, as seen by both tensiometric and scattering measurements.

Influence of tail group length, amide functionality and added salt ion identity on the behaviour of betaine surfactants

Hypothesis The behaviour of surfactants in solution and at interfaces is governed by a combination of steric and electrostatic effects experienced by surfactant molecules as they interact with solvent, other species in solution, and each other. It would therefore be anticipated that highly interacting groups would significantly influence surfactant behaviour. The widely used amide functionality has polar H-bond donor/acceptor properties, and therefore its inclusion into a surfactant structure should have a profound effect on surface activity and self-assembly of that surfactant when compared to the equivalent molecule without an amide linker. Further, chaotropic or kosmotropic salt ions that affect water structuring and hydrogen bonding may provide opportunities for further tuning surfactant interactions in such cases. Experiments A library of betaine surfactant with tail lengths n=14-22 both with and without an amidopropyl linker were synthesised to study the effect of the amide functionality on surfactant properties. Characterisation of the molecules interfacial properties were performed using pendant drop tensiometry and their solution state formulation properties were probed using small-angle neutron scattering (SANS) and rheological measurements. Findings Presence of an amidopropyl linker had little effect on aggregation propensity (as evidenced by critical micelle concentration) and aggregate morphology of betaine surfactants, but did increase the Krafft temperature of these surfactants. SANS analysis indicated that aggregate morphology of alkyl betaine surfactants could be influenced by the addition of sodium salts with chaotropic counterions (I- and SCN-), but they were insensitive to more kosmotropic anions (SO42-, F- and Cl-), providing unique and novel solution control methods for this (supposedly salt-insensitive) class of surfactants.

Trends in the Diversification of the Detergentome

Detergents are amphiphilic molecules that serve as enabling steps for today's world applications. The increasing diversity of the detergentome is key to applications enabled by detergent science. Regardless of the application, the optimal design of detergents is determined empirically, which leads to failed preparations, and raising costs. To facilitate project planning, here we review synthesis strategies that drive the diversification of the detergentome. Synthesis strategies relevant for industrial and academic applications include linear, modular, combinatorial, bio-based, and metric-assisted detergent synthesis. Scopes and limitations of individual synthesis strategies in context with industrial product development and academic research are discussed. Furthermore, when designing detergents, the selection of molecular building blocks, i. e., head, linker, tail, is as important as the employed synthesis strategy. To facilitate the design of safe-to-use and tailor-made detergents, we provide an overview of established head, linker, and tail groups and highlight selected scopes and limitations for applications. It becomes apparent that most recent contributions to the increasing chemical diversity of detergent building blocks originate from the development of detergents for membrane protein studies. The overview of synthesis strategies and molecular blocks will bring us closer to the ability to predictably design and synthesize optimal detergents for challenging future applications.

Development and stability of intimate soap formulations using Sapindus saponaria L. extract as a natural surfactant

The use of synthetic surfactants reflects the high demand in the hygiene and cleaning sector for products with low-cost and good-effectiveness. These ingredients are the main components of intimate soap formulations. Sapindus saponaria L. is a plant rich in saponins, with the potential to be used as a natural surfactant due to its amphiphilic character and its foam-forming properties. Therefore, this study aimed to develop intimate soap formulations using S. saponaria extract as a natural surfactant and analyze its stability and surfactant characteristics. Preliminary and accelerated stability parameters, rheological characteristics, surface tension, foaming power, foam stability and emulsification potential were evaluated. The formulations were stable at a pH suitable for the intimate region (4.0 to 4.5), the presence of S. saponaria extract provided greater reduction of surface tension, better foaming and foam stability and greater emulsification power, desirable characteristics for an intimate liquid soap. These results demonstrate that the incorporation of S. saponaria extract into liquid soap formulations is an excellent option as a natural surfactant to reduce the use of synthetic anionic surfactants such as SLES.

Five dimensions of cleansing: A holistic view on the facets and importance of skin cleansing

Cleansing is an important human ritual practised for hygiene, well-being and relaxation over centuries. As part of body care it is often taken for granted, yet its relevance cannot be underestimated. Although cleansing the skin may seem trivial to some, it is accepted, that this fundamental function of skin cleansing products is highly complex, diverse and crucial for a variety of reasons in the personal, public, healthcare and dermatological settings. Employing a comprehensive and strategic approach in viewing cleansing and its rituals, supports innovation, understanding and development. Apart from being a fundamental function, as far as we know, there is no comprehensive presentation of skin cleansing with all its effects besides 'removing dirt'. To our knowledge, comprehensive analyses on the multi-dimensional facets of skin cleansing are either rare or not published. Against this background, we examine the importance of cleansing in terms of function, relevance and concepts. First, the key functions and efficacies of skin cleansing were investigated by literature research. Based on this survey, the functions were analysed, sorted and merged and a novel approach to skin cleansing 'dimensions' was developed. Herewith, we took into consideration the evolution of skin cleansing in terms of concept evolution, complexity and testing methods for cleansing products and their claims. Several multi-dimensional functions of skin cleansing were identified and then established into five skin cleansing dimensions, namely: hygienic and medical importance; socio-cultural and interpersonal relevance; mood, emotion and well-being; cosmetic and aesthetic function; corneobiological interactions. It became obvious, that these five dimensions with their corresponding 11 sub-dimensions, are influenced by each other throughout history by culture and society, technical progress, scientific knowledge and consumer trends. This article presents the enormous complexity of skin cleansing. Skin cleansing has evolved from basic care up to a highly complex and diverse cosmetic product category in terms of technology, efficacy and usage routine(s). In view of future challenges, such as the effects of climate and associated lifestyle changes, the development of skin cleansing will remain an exciting and important topic and thus will finally, again, further increase the complexity of skin cleansing itself.

Graphene quantum dot doped viscoelastic lyotropic liquid crystal nanocolloids for antibacterial applications

Graphene quantum dots (GQDs) are prepared and characterized via X-ray diffraction (XRD), UV-Visible spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence (PL). GQDs are doped (5 mg and 10 mg) in the lyotropic liquid crystalline (LLC) lamellar and hexagonal phases to prepare GQD/LLC nanocolloids. Polarizing optical microscopy and X-ray diffraction measurement reveals that GQDs do not affect the lamellar and hexagonal LLC structures and may organize on their interface. Pure LLC phases and nanocolloids are studied for steady and dynamic rheological behavior. LLC phases and GQD/LLC nanocolloids possess shear thinning and frequency dependent liquid viscoelastic behavior. A complex moduli study of LLCs and GQD/LLC nanocolloids is carried out which indicates the gel to viscous transition in LLCs and GQD/LLC nanocolloids as a function of frequency. LLC phases and GQD/LLC nanocolloids are tested for antibacterial activity against Listeria ivanovii. The effect of surfactant concentration, LLC phase geometry and GQD concentration has been studied and discussed. A probable mechanism for the strong antimicrobial activity of LLCs and GQD/LLC nanocolloids is presented considering intermolecular interactions. The viscoelastic behavior and strong antibacterial activity (inhibition zone 49.2 mm) of LLCs and GQD/LLC nanocolloids make them valuable candidates for lubrication, cleaning, cosmetics and pharmaceutical applications.

Effects of surfactant adsorption on the wettability and friction of biomimetic surfaces

The properties of solid-liquid interfaces can be markedly altered by surfactant adsorption. Here, we use molecular dynamics (MD) simulations to study the adsorption of ionic surfactants at the interface between water and heterogeneous solid surfaces with randomly arranged hydrophilic and hydrophobic regions, which mimic the surface properties of human hair. We use the coarse-grained MARTINI model to describe both the hair surfaces and surfactant solutions. We consider negatively-charged virgin and bleached hair surface models with different grafting densities of neutral octadecyl and anionic sulfonate groups. The adsorption of cationic cetrimonium bromide (CTAB) and anionic sodium dodecyl sulfate (SDS) surfactants from water are studied above the critical micelle concentration. The simulated adsorption isotherms suggest that cationic surfactants adsorb to the surfaces via a two-stage process, initially forming monolayers and then bilayers at high concentrations, which is consistent with previous experiments. Anionic surfactants weakly adsorb via hydrophobic interactions, forming only monolayers on both virgin and medium bleached hair surfaces. We also conduct non-equilibrium molecular dynamics simulations, which show that applying cationic surfactant solutions to bleached hair successfully restores the low friction seen with virgin hair. Friction is controlled by the combined surface coverage of the grafted lipids and the adsorbed CTAB molecules. Treated surfaces containing monolayers and bilayers both show similar friction, since the latter are easily removed by compression and shear. Further wetting MD simulations show that bleached hair treated with CTAB increases the hydrophobicity to similar levels seen for virgin hair. Treated surfaces containing CTAB monolayers with the tailgroups pointing predominantly away from the surface are more hydrophobic than bilayers due to the electrostatic interactions between water molecules and the exposed cationic headgroups.

Dilution-Induced Deposition of Concentrated Binary Mixtures of Cationic Polysaccharides and Surfactants

This work investigates the effect of dilution on the phase separation process of binary charged polysaccharide-surfactant mixtures formed by two cationic polysaccharides and up to four surfactants of different nature (anionic, zwitterionic, and neutral), as well as the potential impact of dilution-induced phase separation on the formation of conditioning deposits on charged surfaces, mimicking the negative charge and wettability of damaged hair fibers. The results obtained showed that the dilution behavior of model washing formulations (concentrated polysaccharide-surfactant mixtures) cannot be described in terms of a classical complex precipitation framework, as phase separation phenomena occur even when the aggregates are far from the equilibrium phase separation composition. Therefore, dilution-enhanced deposition cannot be predicted in terms of the worsening of colloidal stability due to the charge neutralization phenomena, as common phase separation and, hence, enhanced deposition occurs even for highly charged complexes.

Considering the risk of a coloring shampoo with the function of gray hair cover cosmetology and skin barrier: A systematic review

Background and Aims

As the number of demanders who want to easily cover gray hair increases, the demand market is rapidly expanding along with the demand for coloring shampoos that can be dyed while shampooing. Among these coloring shampoo ingredients, it is necessary to differentiate products that are safe and harmless to the human body in consideration of hair loss or skin barrier problems caused by trihydroxybenzene (THB) ingredients. The correct selection criteria were presented by examining the problems, effectiveness, and side effects when used in relation to the skin barrier through previous studies by consideration of the ingredients of the coloring shampoo and the skin barrier of the scalp.

Methods

The analysis of this study looked at previous studies through a systematic literature review through related keywords for coloring shampoo. After reviewing 150-200 related prior papers, a total of 39 review papers were finally selected using the PRISMA flow diagram.

Results

It was confirmed through a literature review that the coloring shampoo containing THB, which is harmful to the human body, has a detrimental effect on the scalp-skin barrier.

Conclusion

This study examined the harmfulness of coloring shampoo on the scalp skin barrier. It was confirmed that frequent coloring shampoo procedures can have various harmful effects on the scalp. Therefore, it is important to reduce side effects caused by the use of harmful ingredients and maintain a healthy scalp condition through analysis of sufficient scalp conditions and consultation with experts. In addition, various studies on the standard standards and age for harmful ingredients are suggested.

Rhamnolipid Self-Aggregation in Aqueous Media: A Long Journey toward the Definition of Structure–Property Relationships

The need to protect human and environmental health and avoid the widespread use of substances obtained from nonrenewable sources is steering research toward the discovery and development of new molecules characterized by high biocompatibility and biodegradability. Due to their very widespread use, a class of substances for which this need is particularly urgent is that of surfactants. In this respect, an attractive and promising alternative to commonly used synthetic surfactants is represented by so-called biosurfactants, amphiphiles naturally derived from microorganisms. One of the best-known families of biosurfactants is that of rhamnolipids, which are glycolipids with a headgroup formed by one or two rhamnose units. Great scientific and technological effort has been devoted to optimization of their production processes, as well as their physicochemical characterization. However, a conclusive structure–function relationship is far from being defined. In this review, we aim to move a step forward in this direction, by presenting a comprehensive and unified discussion of physicochemical properties of rhamnolipids as a function of solution conditions and rhamnolipid structure. We also discuss still unresolved issues that deserve further investigation in the future, to allow the replacement of conventional surfactants with rhamnolipids.

Thermodynamics of Aggregation between the Cationic Surfactant and Polymer Based on Biodegradable Poly(vinyl Alcohol)

The formation of aggregates between carboxylated (PVCOOH) or neutral hydrolyzed (PVOH) poly(vinyl alcohol) and hexadecylpyridinium chloride (C₁₆PyCl) was examined by conductimetry, turbidimetry, and isothermal titration calorimetry (ITC) in the presence of different NaCl concentrations. The interaction between the polymers and C₁₆PyCl in pure water showed a critical aggregation concentration (cac = 0.8 mmol L^-1) only for the neutral polymer. PVCOOH interacted with the surfactant through electrostatic attraction, forming macroscopic aggregates. Integral enthalpy changes for aggregate formation (ΔH_agg) obtained from ITC curves varied from -0.61 (for the PVOH system in pure water) to -4.14 kJ mol^-1 (for PVOH in the presence of 10.0 mmol L^-1 NaCl), indicating that the formation of the aggregates was enthalpically favored. However, hydrophobic interactions drove the process for low surfactant concentration for both polymers. Saturation concentrations (C2) obtained from conductimetry were smaller than those from ITC, revealing that the binding of C₁₆PyCl on the chain of the polymers at higher surfactant concentrations shows the same electric properties as that of free micelles on the solution. Increase of the ionic strength favored the aggregation and decreased the complexity of the ITC curves, suggesting that the reorganization of the surfactant monomers on the polymeric chain with the increase in their concentration was suppressed.

Polyelectrolyte/Surfactant Mixtures: A Pathway to Smart Foams

This review deals with liquid foams stabilized by polyelectrolyte/surfactant (PS) complexes in aqueous solution. It briefly reviews all the important aspects of foam physics at several scales, from interfaces to macroscopic foams, needed to understand the basics of these complex systems, focusing on those particular aspects of foams stabilized by PS mixtures. The final section includes a few examples of smart foams based on PS complexes that have been reported recently in the literature. These PS complexes open an opportunity to develop new intelligent dispersed materials with potential in many fields, such as oil industry, environmental remediation, and pharmaceutical industry, among others. However, there is much work to be done to understand the mechanism involved in the stabilization of foams with PS complexes. Understanding those underlying mechanisms is vital to successfully formulate smart systems. This review is written in the hope of stimulating further work in the physics of PS foams and, particularly, in the search for responsive foams based on polymer-surfactant mixtures.

Surface Activity of Surfactant–Polyelectrolyte Mixtures through Nanoplasmonic Sensing Technology

Deposition plays an important role in the active delivery and efficiency of hair and skin formulations since it allows active compounds to interact with surfaces in order to achieve the product’s desired performance characteristics. Therefore, it is essential to study the surface activity and behavior of certain compounds that are frequently used in cosmetic and pharmaceutical formulations in order to understand how they interact with relevant biological surfaces, such as hair and skin. We chose to study the surfactants and conditioning agents utilized in the formulation of conditioning shampoos, which are usually designed to be able to achieve the deposition of these substances on the hair and scalp to provide lubrication and better conditioning for hair fibers, facilitating detangling and providing a better feel. In this study, cationic polymer and salt fractions were varied to obtain eighteen different conditioning shampoo formulations in which the deposition was measured by utilizing a nanoplasmonic sensing technology instrument. Moreover, a wet combing test was performed for each of the formulations to investigate if there was any correlation between the combing force and the surface deposition. The complete study was performed using a sustainable anionic surfactant in order to compare the results with those obtained from the traditional formulations.

Phase behavior of the sodium lauryl glutamate: effects of the temperature and concentration

The physical and chemical properties of sodium lauryl glutamate were systematically investigated in this work. To determine the critical micelle concentration (CMC) of sodium lauryl glutamate, the surface tension was measured using the Wilhelmy plate method. The Krafft point was determined using the ultraviolet/visible spectrophotometer. The effect of pH on the solute in the solution was studied using potentiometric titration. The critical packing parameter (CPP) and Gibbs free energy (ΔG) of micelle formation were calculated using the corresponding parameters. The temperature-concentration phase diagram of sodium lauryl glutamate was constructed using the dynamic light scattering system (DLS) and polarised optical microscopy (POM). The calculated theoretical data were combined with the actual observed data from the phase diagram. Finally, the phase behaviour of sodium lauryl glutamate was determined.

Hydrogel Formation by Glutamic-acid-based Organogelator Using Surfactant-mediated Gelation

Hydrogels formed by low-molecular-weight gelators have reversible sol-gel transition and responsiveness to various stimuli, and are used in cosmetics and drug applications. It is challenging to obtain hydrogels using novel gelators because subtle differences in their molecular architecture affect gelation. Organogelators (which form organogels) are insoluble in water, and their use as hydrogelators has not previously been considered. However, a surfactant-mediated gelation method was reported in which organogelators were solubilized in water by surfactants to form hydrogels using 12-hydroxyoctadecanoic acid. To investigate whether this method can be applied with other organogelators, the formation of hydrogel using a glutamic-acid-based organogelator was studied here. Hydrogels were formed by solubilizing 1:1 mixtures of glutamate-based organogelators, N-lauroyl-L-glutamic acid dibuthylamide, and N-2-ethylhexanoyl-L-glutamic acid dibutylamide in aqueous micellar solutions of anionic surfactant (sodium lauroyl glutamate) and cationic surfactant (cetyltrimethylammonium chloride). The minimum gelation concentration of the hydrogel was ~0.2-0.6 wt%. By changing the molar fraction of cetyltrimethylammonium chloride in the mixed surfactant, either spherical or wormlike micelles were formed. The hydrogel with wormlike micelles had a higher sol-gel transition temperature than that with spherical micelles and formed fine self-assembled fibrillar networks. Additionally, the hydrogel with the spherical micelles was elastic, whereas that with wormlike micelles was viscoelastic, suggesting that networks of the organogelators and wormlike micelles coexisted in the hydrogel from the wormlike micellar solution. Moreover, the hydrogel suppressed the reduction in the storage modulus at higher temperatures compared with the micellar aqueous solution, indicating that the elastic properties of the organogelator networks were maintained at high temperatures. The gel fibers of the hydrogel partially formed a loosely aggregated structure as the temperature increased, the fibers bundled via hydrophobic interactions, and new cross-linking points formed spontaneously. This phenomenon corresponded with an inflection point in the temperature-dependent storage modulus of the hydrogel.

A Sebum-Mimetic Lipid Monolayer and Its Interaction with (Bio)Surfactants

Surfactants present in cleansing formulations interact not only with the unwanted lipids accumulating on the human skin (dirt) but also with its protective lipidic layer (sebum). Development of simple models of human sebum would help to compare different surfactants and biosurfactants under the same conditions. In this contribution we propose a first monolayer model of synthetic sebum composed of lard, stearic acid, lanolin, squalane and cholesterol. The monolayer compression isotherm features a gas-liquid (G-LE1), two liquid-liquid transitions (LE1-LE2 and LE2-LC), and a collapse at πcoll = 45 mN/m. The monolayer spread on pure water and pre-compressed to π0 = 30 mN/m was exposed to four synthetic surfactants (sodium lauryl sulfate (SLS), sodium laureth sulfate (SLES), ammonium lauryl sulfate (ALS) and cocamidopropyl betaine (CAPB)) and four plant extracts (oat (Avena sativa L.), horse chestnut (Aesculus hippocastanum L.), cowherb (Vaccaria hispanica [P. Mill.] Rauschert), soybean (Glycine max L.) and soapwort (Saponaria officinalis L.)) introduced to the subphase at a dry mass content of 1% (w/w). Three modes of the monolayer-(bio)surfactant interactions were observed: (1) complete solubilization (SLS, SLES, ALS, CAPB); (2) penetration accompanied by an increase of surface pressure and elasticity but without solubilization (horse chestnut, cowherb, soapwort); (3) no interaction (oat, soybean).

Solution Structures of Anionic-Amphoteric Surfactant Mixtures near the Two-Phase Region at Fixed pH

We examine the solution structures in a mixed surfactant system of sodium dodecyl sulfate (SDS) and N,N-dimethyldodecylamine N-oxide (DDAO) in water, on both sides of the two-phase boundary, employing dynamic light scattering, small-angle neutron scattering, and Fourier transform infrared spectroscopy. The precipitate phase boundary was accessed by lowering pH to 8, from its floating pH 9.5 value, and was experimentally approached from the monomeric and micellar regions in three ways: at fixed DDAO or SDS concentrations and at a fixed (70:30) SDS:DDAO molar ratio. We characterize the size, shape, and interactions of micelles, which elongate approaching the boundary, leading to the formation of disk-like aggregates within the biphasic region, coexisting with micelles and monomers. Our data, from both monomeric and micellar solutions, indicate that the two phase structures formed are largely pathway-independent, with dimensions influenced by both pH and mixed surfactant composition. Precipitation occurs at intermediate stoichiometries with a similar SDS:DDAO ratio, whereas asymmetric stoichiometries form a re-entrant transition, returning to the mixed micelle phase. Overall, our findings demonstrate the effect of stoichiometry and solution pH on the synergistic interaction of mixed surfactants and their impact on phase equilibrium and associated micellar and two-phase structures.

Study of the Dilution-Induced Deposition of Concentrated Mixtures of Polyelectrolytes and Surfactants

Mixtures of polyelectrolytes and surfactants are commonly used in many technological applications where the challenge is to provide well-defined modifications of the surface properties, as is the case of washing formulations in cosmetics. However, if contemporary experimental and theoretical methods can provide insights on their behavior in concentrated formulations, less is known on their behavior under practical use conditions, e.g., under dilution and vectorization of deposits. This makes it difficult to make predictions for specific performance, as, for example, good hair manageability after a shampoo or a comfortable sensorial appreciation after a skin cleanser. This is especially important when considering the formulation of new, more eco-friendly formulations. In this work, a detailed study of the phase separation process induced by dilution is described, as well as the impact on the deposition of conditioning material on negatively charged surfaces. In order to gain a more detailed physical insight, several polyelectrolyte–surfactant pairs, formed by two different polymers and five surfactants that, although non-natural or eco-friendly, can be considered as models of classical formulations, have been studied. The results evidenced that upon dilution the behavior, and hence its deposition onto the surface, cannot be predicted in terms of the behavior of simpler pseudo-binary (mixtures of a polymer and a surfactant) or pseudo-ternary mixtures (two polymers and a surfactant). In many cases, phase separation was observed for concentrations similar to those corresponding to the components in some technological formulations, whereas the latter appeared as monophasic systems. Therefore, it may be assumed that the behavior in multicomponent formulations is the result of a complex interplay of synergistic interactions between the different components that will require revisiting when new, more eco-sustainable ingredients are considered.

Skin Cleansing without or with Compromise: Soaps and Syndets

Products designed to cleanse the skin commonly do so through surfactant action, which leads to the lowering of the surface tension of the skin to facilitate the removal of dirt from its surface. Skin cleansers generally come in one of two types: soap-based and synthetic detergents, or syndets. While the latter can effectively maintain the native skin structure, function and integrity, the former tends to negatively affect the skin by causing barrier disruption, lipid dissolution and pH alteration. Despite this, soap is still often preferred, possibly due to the negative connotations around anything that is not perceived as 'natural'. It is, therefore, important that the science behind cleansers, especially those designed for the maintenance of healthy skin and the management of common skin conditions such as eczema, be understood by both formulators and end-users. Here, we carefully weigh the advantages and disadvantages of the different types of surfactant-the key ingredient(s) in skin cleansers-and provide insight into surfactants' physicochemical properties, biological activity and potential effects. Fine-tuning of the complex characteristics of surfactants can successfully lead to an 'optimal' skin cleanser that can simultaneously be milder in nature, highly effective and beneficial, and offer minimal skin interference and environmental impact.

Bacteriostasis and cleaning effect of trace ozone replacing personal care products

Ozone is widely used to inactivate bacteria, fungi, and viruses. In recent years, the treatment of itchy skin diseases (eczema and atopic dermatitis) using trace ozone has also received attention. However, the feasibility of using trace ozone to replace personal care products (PCPs) has rarely been analyzed. In this study, the applicability of trace ozone was evaluated in terms of its efficiency for microbial inactivation in three types of skin microbiomes, cleaning performance on simulated human hair and epidermis, safety for simulated human hair, and contribution to emission reduction. The results revealed that at a 10:1 ratio of ozonated water to bacterial suspension, the inactivation ratios of Malassezia, C. albicans, and S. epidermidis reached 99.63%, 83.47%, and 100%, respectively. In addition, the cleaning performance of an ozone solution (0.4 mg/L) for simulated human skin contaminated with carbon black and sebum could reach 95.89% and 95.63%, respectively, with 5 min of washing. The average scores were 0.40 and 0.37 after 5 min and 10 min of ozone treatments, respectively, indicating that trace ozone does not significantly damage simulated human hair. Results also revealed that the total emissions of COD, TP, and TN would be reduced by 1.29×10⁶, 3.55×10³, and 3.63×10³ mg/ (household · year), respectively, if PCPs are replaced by trace ozone. In short, our findings indicate that trace ozone is a potential alternative to PCPs. By replacing PCPs with trace ozone, the use of synthetic chemical products can be reduced and carbon emissions from oil extraction can be countered.

New antioxidant lauryl-free herbal shampoo formulation with a Brazilian plant extract

Abstract Sodium lauryl sulfate is the main cleaning ingredient in shampoos, even though it may be potentially damaging to hair. The demand for antioxidant-rich cosmetics, on the other hand, has encouraged green cosmetics research. Brazil has vast biodiversity that can be exploited for the production of these cosmetics. This work aimed to develop a minimalist antioxidant lauryl-free shampoo formulation with leaf extracts from the Brazilian plant Hancornia speciosa Gomes. Two hydroethanolic extracts were prepared using different extraction methods, Soxhlet, and ultrasound. The extracts were characterized by the presence of saponins, polyphenol quantification, and HLPC chemical identification of the compounds. Antioxidant activity was determined using the DPPH method. The antioxidant lauryl-free shampoo was developed using hydroxyethyl cellulose with two concentrations of leaf extract obtained by Soxhlet, 0.125 mg/g (XP1) and 0.250 mg/g (XP2). Along with the antioxidant activity, the physical and chemical properties, cleaning potential, and foam quality were evaluated. The Soxhlet leaf extract revealed a more favorable chemical profile, including a positive result for saponins, as well as a larger quantity of polyphenols and increased antioxidant activity. The XP2 formulation showed better foam height, dirt dispersion, and antioxidant activity. Thus, the use of mangabeira leaf extract appears to be promising for the development of shampoos with antioxidant activity.

Heads or tails? The synthesis, self-assembly, properties and uses of betaine and betaine-like surfactants

Betaines are a key class of zwitterionic surfactant that exhibit particularly favorable properties, making them indispensable in modern formulation. Due to their composition, betaines are readily biodegradable, mild on the skin and exhibit some antimicrobial activity. Vital to their function, these surfactants self-assemble into diverse micellar geometries, some of which contribute to increased solution viscosity, and their surface activity results in strong detergency and foaming. As such, their behavior has been exploited in various applications from personal care (including shampoos and liquid soaps) to specific industrial fields (such as enhanced oil recovery). This review aims to inform the reader of the diverse range of different betaine and betaine-like surfactants that have been actively researched over the past three decades. Synthesis as well as both chemical and physical characterization of betaine surfactants are discussed, including small-angle scattering studies that indicate self-assembly structures and rheological data that demonstrates texture and flow. Stimulus responsive systems and exotic betaine analogs with enhanced functionality are also covered. Crucially, the connection between surfactant molecular architecture and function are highlighted, exemplifying precisely why zwitterionic betaine and related surfactants are so uniquely functional.

Urea induces (unexpected) formation of lamellar gel-phase in low concentration of cationic surfactants

HYPOTHESIS

The unexpected formation of a lamellar structure with concomitant gelation in solutions containing high urea concentration (40 wt%) and relatively low amount of cationic surfactant (3 wt%), indicates that a hierarchically structured complex is formed by both molecules.

EXPERIMENTS

Gels formed by combination of aqueous solutions of urea and C₁₂TAB, C₁₄TAB or C₁₆TAB were prepared in different proportions and their structures at microscopic and mesoscopic levels were investigated using XRD and SAXS, respectively. The elastic and viscous moduli and yield stress of the samples were determined and correlated with the composition and structuration of the gels. The lamellar structure is reversibly thermically destroyed and this process was investigated using DSC.

FINDINGS

XRD revealed that, at microscopic scale, the gels are formed through crystallization of adducts containing surfactant molecules loaded into the cavities of honeycomb-like urea assemblies. Such crystalline phase arranges itself in lamellae with interplanar distance around ∼20-30 nm, which were observed by SAXS. This hierarchical structure is independent of the chain length of the cationic surfactants. The blocks of lamellae dispersed in the continuous phase form a three-dimensional rigid particulate network structure, giving the characteristic rheological behavior of a hydrogel. DSC revealed a reversible thermal transition at around 20-25 °C, beyond which the adducts and the lamellar phase are destroyed and micelles are formed. The characteristic transition temperature is independent of the chain length of the surfactant, and thus, it is not associated with their Krafft temperatures. The structures of the gels indicate that they resemble alpha-gels formed by fatty-alcohols and surfactants, although they self-assemble by different driving forces.

Surface Properties and Liquid Crystal Properties of Alkyltetra(oxyethyl) β-d-Glucopyranoside

Hydrophilic alkyl polyglycosides (APGs) and alkyl glycosides (AGs) with anomeric pure are a class of important substitutes for petroleum-based surfactants. Improving their water solubility should make such hydrophilic glycosurfactants have more excellent potential application value. To solve the inherent problem of poor water solubility of traditional alkyl β-d-glucopyranoside (5), a series of alkyltetra(oxyethyl) β-d-glucopyranosides (4a-4g, n = 7-18) were successfully synthesized by introducing tetra(oxyethylene) fragments to carry out the structural modification. The relationship between the related structure and the physicochemical properties was further investigated, including their hydrophilic-lipophilic balance (HLB), water-solubility, foaming performance, emulsification, hygroscopicity, surface activity, and thermotropic/lyotropic liquid crystal phase behavior. The results showed that the water solubility gradually decreased as the alkyl chain length increased due to the gradual decrease of their HLB number. Octadecyltetra(oxyethyl) β-d-glucopyranoside (4g, n = 18) was found to be insoluble in water at 25 °C. Taken together, long-chain alkyl glycosides had good foaming properties and excellent emulsifying properties. Among them, dodecyltetra(oxyethyl) β-d-glucopyranoside (4d, n = 12) had the best foaming performance. In the rapeseed oil/water system, cetyltetra(oxyethyl) β-d-glucopyranoside (4f, n = 16) had the best emulsifying ability. With the increase of the alkyl chain length, the critical micelle concentration (C_cmc), γ_cmc, Γ_max, and hygroscopicity of this series of glycosides showed a downward trend. Differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) showed that the thermal stability increased with the increase of the alkyl chain length, and alkyltetra(oxyethyl) β-d-glucopyranosides (4d-4g, n = 12-18) had the corresponding melting points and clearing points. Alkyltetra(oxyethyl) β-d-glucopyranosides (4b-4g, n = 8-18) formed a smectic phase with a typical fan-shaped and focal conic texture during the cooling process. In the water contact experiments, it was found that glycosides (4b-4g, n = 8-18) at high concentrations transformed into various lyotropic liquid crystal including hexagonal phase, bicontinuous cubic phase, and lamellar phase phases. Therefore, such green nonionic glycosurfactants alkyltetra(oxyethyl) β-d-glucopyranosides should have potential practical application prospects.

Salt- and pH-Dependent Viscosity of SDS/LAPB Solutions: Experiments and a Semiempirical Thermodynamic Model

We present novel data on the composition-, pH-, and salt-dependent zero shear viscosity of the commercially important mixture of anionic sodium dodecyl sulfate (SDS) and zwitterionic lauramidopropyl betaine (LAPB). We show via proton NMR experiments that the notionally zwitterionic LAPB exhibits a large pK_a shift in the presence of SDS and can become partially cationic at formulation-relevant pH ranges of 4.5-6.0-that is, the binary system is effectively a ternary system. This has a pronounced effect on the viscosity of the system at low pH, especially if the fraction of LAPB is high. We use theoretical arguments to motivate a semiempirical but practical approach to model the viscosity of the mixtures using thermodynamic parameters such as the excess chemical potentials or activity coefficients of the surfactants. We demonstrate this using an augmented regular solution theory-based mixed micelle thermodynamic model and develop robust regression models using Bayesian approaches. We also show how the pK_a shift from NMR experiments can be used to parameterize the thermodynamic model. This framework should be extensible to other arbitrary surfactant mixtures in the future and hence will be of broad interest for the development of surfactant formulations for household, personal care, and other applications.

The Use of Catalytic Amounts of Selected Cationic Surfactants in the Design of New Synergistic Preservative Solutions

Preservation using combinations of antibacterial molecules has several advantages, such as reducing the level of usage and broadening their antimicrobial spectrum. More specifically, the use of quaternary ammonium surfactants (QAS)—which are profusely used in hair care products and some are known as efficient antimicrobial agents—is limited due to some potential cytotoxicity concerns. This study shows that the concentration of some widely used cosmetic preservatives can be decreased when combined with very small quantities of QAS, i.e., Polyquaternium-80 (P-80) and/or Didecyldimethylammonium chloride (DDAC). The antimicrobial activity of their mixtures was first evaluated by determining the minimum inhibitory concentration (MIC) before and after the addition of QAS. Following up on this finding and targeting an ultimate consumer friendly antimicrobial blend, yet with optimal safety, we chose to utilize the food-grade preservative Maltol as the main natural origin antimicrobial agent mixed with minimum concentrations of QAS to improve its moderate antimicrobial properties. The preservatives were tested for MIC values, challenge tests and synergy using the fractional inhibitory concentration index (FICI). The antimicrobial efficacy of Maltol was found to be synergistically improved by introducing catalytic amounts of P-80 and/or DDAC.

Correlations between the Type of Aggregates in the Bulk Phase and the Functionality and Safety of All-Purpose Cleaners

The article shows that the type and concentration of inorganic salt can be translated into the structure of the bulk phase and the performance properties of ecological all-purpose cleaners (APC). A base APC formulation was developed. Thereafter, two types of salt (sodium chloride and magnesium chloride) were added at various concentrations to obtain different structures in the bulk phase. The salt addition resulted in the formation of spherical micelles and-upon addition of more electrolyte-of aggregates having a lamellar structure. The formulations had constant viscosities (ab. 500 mPa·s), comparable to those of commercial products. Essential physical-chemical and performance properties of the four formulations varying in salt types and concentrations were evaluated. It was found that the addition of magnesium salt resulted in more favorable characteristics due to the surface activity of the formulations, which translated into adequately high wettability of the investigated hydrophobic surfaces, and their ability to emulsify fat. A decreasing relationship was observed in foaming properties: higher salt concentrations lead to worse foaming properties and foam stability of the solutions. For the magnesium chloride composition, the effect was significantly more pronounced, as compared to the sodium chloride-based formulations. As far as safety of use is concerned, the formulations in which magnesium salt was used caused a much lesser irritation compared with the other investigated formulations. The zein value was observed to decrease with increasing concentrations of the given type of salt in the composition.

Determination of SLES in Personal Care Products by Colloid Titration with Light Reflection Measurements

The method of colloid titration with poly(diallyldimethylammonium) chloride has been improved to detect the endpoint with an off-vessel light reflectance sensor. The digital color sensor used measures light reflectance by means of light guides, with no immersion into the reaction solution. In such a method, the optical signal is free of disturbances caused by sticky flocs in the solution. The improved automatic titration set was applied for the determination of sodium laureth sulfate (SLES) in industrial batches and commercial personal care products. The sample color and opacity do not disturb the SLES quantification. When the SLES content lies in the range from 5% to 9%, the optimal sample weight is from 6 g to 3 g.

Nanocomposite gels of poloxamine and Laponite for β-Lapachone release in anticancer therapy

Nano-hybrid systems have been shown to be an attractive platform for drug delivery. Laponite® RD (LAP), a biocompatible synthetic clay, has been exploited for its ability to establish of strong secondary interactions with guest compounds and hybridization with polymers or small molecules that improves, for instance, cell adhesion, proliferation, and differentiation or facilitates drug attachment to their surfaces through charge interaction. In this work, LAP was combined with Tetronics, X-shaped amphiphilic PPO-PEO (poly (propylene oxide)-poly (ethylene oxide) block copolymers. β-Lapachone (BLPC) was selected for its anticancer activity and its limited bioavailability due to very low aqueous solubility, with the aim to improve this by using LAP/Tetronic nano-hybrid systems. The nanocarriers were prepared over a range of Tetronic 1304 concentrations (1 to 20% w/w) and LAP (0 to 3% w/w). A combination of physicochemical methods was employed to characterize the hybrid systems, including rheology, particle size and shape (DLS, TEM), thermal analysis (TG and DSC), FTIR, solubility studies and drug release experiments. In vitro cytotoxicity assays were performed with BALB/3T3 and MCF-7 cell lines. In hybrid systems, a sol-gel transition can occur below physiological temperature. BLPC exhibits the most significant increase in solubility in formulations with a high concentration of T1304 (over 10% w/w) and 1.5% w/w LAP, or systems with only LAP (1.5%), with a 50 and 100-fold increase in solubilisation, respectively. TEM images showed spherical micelles of T1304, which elongated into wormlike micelles with concentration (20%) and in the presence of LAP, a finding that has not been reported before. A sustained release of BLPC over 140 hours was achieved in one of the formulations (10% T1304 with 1.5% laponite), which also showed the best selectivity index towards cancer cells (MCF-7) over BALB/3T3 cell lines. In conclusion, BLPC-loaded T1304/LAP nano-hybrid systems proved safe and highly effective and are thus a promising formulation for anticancer therapy.

Surface science of cosmetic substrates, cleansing actives and formulations

The development of shampoo and cleansing formulations in cosmetics is at a crossroads due to consumer demands for better performing, more natural products and also the strong commitment of cosmetic companies to improve the sustainability of cosmetic products. In order to go beyond traditional formulations, it is of great importance to clearly establish the science behind cleansing technologies and appreciate the specificity of cleansing biological surfaces such as hair and skin. In this review, we present recent advances in our knowledge of the physicochemical properties of the hair surface from both an experimental and a theoretical point of view. We discuss the opportunities and challenges that newer, sustainable formulations bring compared to petroleum-based ingredients. The inevitable evolution towards more bio-based, eco-friendly ingredients and sustainable formulations requires a complete rethink of many well-known physicochemical principles. The pivotal role of digital sciences and modelling in the understanding and conception of new ingredients and formulations is discussed. We describe recent numerical approaches that take into account the specificities of the hair surface in terms of structuration, different methods that study the adsorption of formulation ingredients and finally the success of new data-driven approaches. We conclude with practical examples on current formulation efforts incorporating bio-surfactants, controlling foaming and searching for new rheological properties.

Synthetic and Bio-Derived Surfactants Versus Microbial Biosurfactants in the Cosmetic Industry: An Overview

This article includes an updated review of the classification, uses and side effects of surfactants for their application in the cosmetic, personal care and pharmaceutical industries. Based on their origin and composition, surfactants can be divided into three different categories: (i) synthetic surfactants; (ii) bio-based surfactants; and (iii) microbial biosurfactants. The first group is the most widespread and cost-effective. It is composed of surfactants, which are synthetically produced, using non-renewable sources, with a final structure that is different from the natural components of living cells. The second category comprises surfactants of intermediate biocompatibility, usually produced by chemical synthesis but integrating fats, sugars or amino acids obtained from renewable sources into their structure. Finally, the third group of surfactants, designated as microbial biosurfactants, are considered the most biocompatible and eco-friendly, as they are produced by living cells, mostly bacteria and yeasts, without the intermediation of organic synthesis. Based on the information included in this review it would be interesting for cosmetic, personal care and pharmaceutical industries to consider microbial biosurfactants as a group apart from surfactants, needing specific regulations, as they are less toxic and more biocompatible than chemical surfactants having formulations that are more biocompatible and greener.

Optimizing interactions between soluble silk fibroin and capryl glucoside for design of a natural and high-performance co-surfactant system

OBJECTIVES

Because of the strong consumer driver towards more natural or higher sustainability cosmetic products, silk fibroin was evaluated to help develop a formulation with natural and effective ingredients for personal care. In order to exploit the physical properties of silk fibroin, it was evaluated to maximize the surfactant properties of other commercial ingredients to lower surface tension and build up viscosity. A synergistic effect was seen between silk fibroin and capryl glucoside, a sugar surfactant which exhibited a natural and effective co-surfactant system. This system demonstrated better surface tension properties than sodium laureth sulphate (SLES), cocamidopropyl betaine (CAPB), rhamnolipids and sophorolipids, which led to greater foamability and cleansing properties. This system proved to also be compatible with polysaccharide viscosity modifiers to enhance the viscosity of the system. The present study comprises a systematic exploration of natural formulation development of silk proteins and other natural ingredients, which result in high performance such as enhanced foam quality, foam stability and enhanced sebum removal. All of these properties are desirable and may utilized when formulating cleaners and shampoos.

METHODS

A force tensiometer, Attension Sigma 701, was used to measure the surface tension of the silk protein and its various combinations with biosurfactants and biopolymers. To measure bulk rheology, a traditional mechanical rheometer TA DHR-3 was utilized. Foaming tests and sebum removal assays were also carried out to evaluate the performance of the samples.

RESULTS

Silk fibroin was evaluated to maximize the surfactant properties of other commercial systems to develop a formulation containing natural and effective ingredients for personal care. The surface activity of silk proteins was seen to be synergistically enhanced in the presence of sugar surfactants such as capryl glucoside, resulting in a surface tension at the air-water interface which is lower than either that of pure silk fibroin or pure capryl glucoside. This surface tension value is additionally lower than that obtained from currently utilized synthetic surfactants like sodium laureth sulphate (SLES) and cocamidopropyl betaine (CAPB). This reduction in surface tension demonstrated greater foamability and cleansing properties than that of the commercial systems. The very low surface tension values obtained through combinations of silk proteins and glucoside resulted in a natural and effective co-surfactant system by forming high-quality stable foams and enhancing sebum removal. The rheological performance of the silk proteins was impacted through microstructure modifications as a result of interactions with biopolymers like carrageenan. This shows that this system is compatible with polysaccharide viscosity modifiers. It was observed that both the flow curve and the absolute viscosity values were significantly impacted in the presence of carrageenan, with higher viscosity generation and significant non-Newtonian/shear thinning behaviour evolution. These results indicate that the silk fibroin can be utilized to build a high-performance natural product and significantly enhance the performance of other natural/sustainable cosmetic formulations through building synergistic interactions with other natural ingredients such as sugar surfactants and biopolymers. These properties exhibited by this system are all desirable for cleansers and shampoos within the cosmetic industry.

CONCLUSION

Silk fibroin in combination with capryl glucoside outperforms other commercial surfactants that are commonly used in the industry because of its surface-active behaviour and synergy. This system is then enhanced further with polysaccharide rheological modifiers, carrageen and xanthan gum to help build up viscosity. The complex mixture of silk fibroin, sugar surfactant and biopolymer results in a formulation that is all natural, while still having high performance by achieving great foamability and enhanced sebum removal. The mixture can further be used to formulate a fully natural product such as a cleanser or shampoo while still having the same or greater effectiveness as synthetic surfactants and ingredients typically used in cosmetic formulations.

In Situ Nanostructural Analysis of Concentrated Wormlike Micellar Fluids Comprising Sodium Laureth Sulfate and Cocamidopropyl Betaine Using Small-Angle Neutron Scattering

Concentrated wormlike micellar fluids form the basis for a vast array of formulated products, from liquid soaps and shampoos to drag reduction and drilling fluids. Typically, these systems are analyzed using bulk rheological measurements to determine their flow properties and cryo-microscopy to detect their nanostructure. Small-angle neutron scattering provides an opportunity to directly and nonperturbatively analyze nanostructure in situ but is complicated for concentrated systems by correlations from interparticle volume exclusion. Here, we use small-angle and ultra-small-angle neutron scattering to probe directly for the first time the nanostructure of concentrated wormlike micellar fluids composed of the widely used surfactant pair sodium laureth sulfate and cocamidopropyl betaine in aqueous electrolytes. Obtained data are analyzed using different approaches to determine scattering contributions from the wormlike particles themselves and interactions between them. It is found that approximating worms as locally rigid cylinders offers some insight into their aggregation dimensions at short length scales, and both volume exclusion and screened Coulombic interaction potentials describe interactions reasonably well. Using the semi-empirical polymer reference interaction site model (PRISM) gives excellent agreement with observed scattering, and physical insight obtained using this approach is discussed in detail. A drawback of this method is the significant complexity in coding the model in order to fit data, so to facilitate this for future researchers, we provide with this paper a fully operational, open-source code to utilize this model.

The Relationship between Wormlike Micelle Scission Free Energy and Micellar Composition: The Case of Sodium Lauryl Ether Sulfate and Cocamidopropyl Betaine

The scission energy is the difference in free energy between two hemispherical caps and the cylindrical region of a wormlike micelle. This energy difference determines the logarithm of the average micelle length, which affects several macroscopic properties such as the viscosity of viscoelastic fluids. Here we use a recently published method by Wang et al. ( Langmuir, 2018, 34, 1564-1573) to directly calculate the scission energy of micelles composed of monodisperse sodium lauryl ether sulfate (SLES_nEO), an anionic surfactant. Utilizing dissipative particle dynamics (DPD), we perform a systematic study varying the number of ethoxyl groups (n) and salt concentration. The scission energy increases with increasing salt concentration, indicating that the formation of longer micelles is favored. We attribute this to the increased charge screening that reduces the repulsion between head groups. However, the scission energy decreases with increasing number of ethoxyl groups as the flexibility of the head group increases and the sodium ion becomes less tightly bound to the head group. We then extend the analysis to look at the effect of a common cosurfactant, cocamidopropyl betaine (CAPB), and find that its addition stabilizes wormlike micelles at a lower salt concentration.

Comparison of Individual and Integrated Inline Raman, Near-Infrared, and Mid-Infrared Spectroscopic Models to Predict the Viscosity of Micellar Liquids

In many industries, viscosity is an important quality parameter which significantly affects consumer satisfaction and process efficiency. In the personal care industry, this applies to products such as shampoo and shower gels whose complex structures are built up of micellar liquids. Measuring viscosity offline is well established using benchtop rheometers and viscometers. The difficulty lies in measuring this property directly in the process via on or inline technologies. Therefore, the aim of this work is to investigate whether proxy measurements using inline vibrational spectroscopy, e.g., near-infrared (NIR), mid-infrared (MIR), and Raman, can be used to predict the viscosity of micellar liquids. As optical techniques, they are nondestructive and easily implementable process analytical tools where each type of spectroscopy detects different molecular functionalities. Inline fiber optic coupled probes were employed; a transmission probe for NIR measurements, an attenuated total reflectance probe for MIR and a backscattering probe for Raman. Models were developed using forward interval partial least squares variable selection and log viscosity was used. For each technique, combinations of pre-processing techniques were trialed including detrending, Whittaker filters, standard normal variate, and multiple scatter correction. The results indicate that all three techniques could be applied individually to predict the viscosity of micellar liquids all showing comparable errors of prediction: NIR: 1.75 Pa s; MIR: 1.73 Pa s; and Raman: 1.57 Pa s. The Raman model showed the highest relative prediction deviation (RPD) value of 5.07, with the NIR and MIR models showing slightly lower values of 4.57 and 4.61, respectively. Data fusion was also explored to determine whether employing information from more than one data set improved the model quality. Trials involved weighting data sets based on their signal-to-noise ratio and weighting based on transmission curves (infrared data sets only). The signal-to-noise weighted NIR-MIR-Raman model showed the best performance compared with both combined and individual models with a root mean square error of cross-validation of 0.75 Pa s and an RPD of 10.62. This comparative study provides a good initial assessment of the three prospective process analytical technologies for the measurement of micellar liquid viscosity but also provides a good basis for general measurements of inline viscosity using commercially available process analytical technology. With these techniques typically being employed for compositional analysis, this work presents their capability in the measurement of viscosity-an important physical parameter, extending the applicability of these spectroscopic techniques.

Impact of wormlike micelles on nano and macroscopic structure of TEMPO-oxidized cellulose nanofibril hydrogels

In this work, we investigated the effect of adding surfactant mixtures on the rheological properties of TEMPO-oxidized cellulose nanofibril (OCNF) saline dispersions. Three surfactant mixtures were studied: cocamidopropyl betaine (CAPB)/sodium dodecyl sulfate (SDS), which forms wormlike micelles (WLMs); cocamidopropylamine oxide (CAPOx)/SDS, which forms long rods; and CAPB/sodium lauroyl sarcosinate (SLS), which forms spherical micelles. The presence of micelles in these surfactant mixtures, independent of their morphology, leads to an increase of tan δ, making the gels less solid-like, therefore acting as a plasticizer. WLMs were able to suppress strain stiffening normally observed in OCNF gels at large strains. OCNF/WLM gels have lower G' values than OCNF gels while the other micellar morphologies have a reduced impact on G'. The presence of unconnected micelles leads to increased dissipative deformation in OCNF gels without affecting the connectivity of the fibrils, while the presence of entangled micelles interferes with the OCNF network.