Colloid, interface, and foam properties of water-soluble polyglycerol esters solutions.

Hypothesis: Polyglycerol esters of fatty acids are generated via the esterification of a polydisperse mixture of polyglycerol with naturally derived fatty acids. The polymerization process of polyglycerol results in the production of various oligomers, ranging from di-, tri-, and higher-order forms, which contribute to the complexity of final products. The combination of complementary experimental techniques and adequate theoretical interpretations can reveal the wide variety of their physicochemical properties.

Manipulating the hydrophilic / hydrophobic balance in novel cationic surfactants by ethoxylation: The impact on adsorption and self-assembly.

Hypothesis: Cationic surfactants have a wide range of applications, often associated with their affinity for a range of solid surfaces and their anti-microbial properties. Manipulating their adsorption and self-assembly properties is key to most applications, and this is commonly achieved through surfactant mixtures or manipulating their headgroup or alkyl chain structure. Achieving this through adjustments to their headgroup structure is less common in cationic surfactants than in anionic surfactants.

Enhanced solubility of methyl ester sulfonates below their Krafft points in mixed micellar solutions.

Hypothesis: Methyl ester sulfonates (MES) show limited water solubility at lower temperatures (Krafft point). One way to increase their solubility below their Krafft points is to incorporate them in anionic surfactant micelles. The electrostatic interactions between the ionic surfactant molecules and charged micelles play an important role for the degree of MES solubility.

Acyl chain length tuning improves antimicrobial potency and biocompatibility of short designed lipopeptides.

Hypothesis: Designed antimicrobial lipopeptides (ALPs) offer the attractive benefits of short peptide sequences and flexible tuning of amphiphilicity by altering the acyl chain length. These lipopeptides kill microbes by forming intriguing in-membrane nanostructures and causing the leakage of internal contents. However, how subtle differences in the molecular structures of the lipopeptides affect their antimicrobial efficacy and biocompatibility to host cells is still under-investigated.

Structural features of interfacially adsorbed acyl-l-carnitines.

Hypothesis: Acyl-l-carnitines (CLCs) are potentially important as biosurfactants in drug delivery and tissue engineering due to their good biocompatibility. However, little is currently known about the basic interfacial behavior underlying their technological applications. Following our previous characterization of their solution aggregation and adsorption at the air/water interface, this work examines how they adsorb at the hydrophilic solid/liquid interface.

In-Membrane Nanostructuring of Cationic Amphiphiles Affects Their Antimicrobial Efficacy and Cytotoxicity: A Comparison Study between a De Novo Antimicrobial Lipopeptide and Traditional Biocides.

Cationic biocides have been widely used as active ingredients in personal care and healthcare products for infection control and wound treatment for a long time, but there are concerns over their cytotoxicity and antimicrobial resistance. Designed lipopeptides are potential candidates for alleviating these issues because of their mildness to mammalian host cells and their high efficacy against pathogenic microbial membranes. In this study, antimicrobial and cytotoxic properties of a de novo designed lipopeptide, CH(CH)CO-Lys-Lys-Gly-Gly-Ile-Ile-NH (CKKGGII), were assessed against that of two traditional cationic biocides CTAB ( = 12 and 14), with different critical aggregation concentrations (CACs).

How do chain lengths of acyl-l-carnitines affect their surface adsorption and solution aggregation?

Hypothesis: l-carnitines in our body systems can be readily converted into acyl-l-carnitines which have a prominent place in cellular energy generation by supporting the transport of long-chain fatty acids into mitochondria. As biocompatible surfactants, acyl-l-carnitines have potential to be useful in technical, personal care and healthcare applications. However, the lack of understanding of the effects of their molecular structures on their physical properties has constrained their potential use.

Solubility of ionic surfactants below their Krafft point in mixed micellar solutions: Phase diagrams for methyl ester sulfonates and nonionic cosurfactants.

Hypothesis: Many ionic surfactants with wide applications in personal-care and house-hold detergency show limited water solubility at lower temperatures (Krafft point). This drawback can be overcome by using mixed solutions, where the ionic surfactant is incorporated in mixed micelles with another surfactant, which is soluble at lower temperatures.

Experiments: The solubility and electrolytic conductivity for a binary surfactant mixture of anionic methyl ester sulfonates (MES) with nonionic alkyl polyglucoside and alkyl polyoxyethylene ether at 5 °C during long-term storage were measured.

Surface adsorption and solution aggregation of a novel lauroyl-l-carnitine surfactant.

Hypothesis: l-carnitine plays a crucial role in the cellular production of energy by transporting fatty acids into mitochondria. Acylated l-carnitines are amphiphilic and if appropriate physical properties were demonstrated, they could replace many currently used surfactants with improved biocompatibility and health benefits.

Experiments: This work evaluated the surface adsorption of lauroyl-l-carnitine (CLC) and its aggregation behavior.

α-Sulfo alkyl ester surfactants: Impact of changing the alkyl chain length on the adsorption, mixing properties and response to electrolytes of the tetradecanoate.

Hypothesis: The α-sulfo alkyl ester, AES, surfactants are a class of anionic surfactants which have potential for improved sustainable performance in a range of applications, and an important feature is their enhanced tolerance to precipitation in the presence of multivalent counterions. It is proposed that their adsorption properties can be adjusted substantially by changing the length of the shorter alkyl chain, that of the alkanol group in the ester.

Experiments: Surface tension and neutron reflectivity have been used to investigate the variation in the adsorption properties with the shorter alkyl chain length (methyl, ethyl and propyl), the impact of NaCl on the adsorption, the tendency to form surface multilayer structures in the presence of AlCl, and the effects of mixing the methyl ester sulfonate with the ethyl and propyl ester sulfonates on the adsorption.

Effect of equilibrium pH on the structure and properties of bleach-damaged human hair fibers.

Hair proteins are significantly affected by environmental pH. This impact tends to increase with prior hair damage. To understand how pH affects bleached hair properties, we utilized a number of techniques allowing for the determination of hair thermal properties, swelling and water sorption, and dry and wet tensile properties.

Vortex in liquid films from concentrated surfactant solutions containing micelles and colloidal particles.

Hypothesis: New dynamic phenomena can be observed in evaporating free liquid films from colloidal solutions with bimodal particle size distribution. Such distributions are formed in a natural way in mixed (slightly turbid) solutions of cationic and anionic surfactants, where nanosized micelles coexist with micronsized precipitated particles.

Experiment: Without evaporation of water, the films thin down to thickness < 100 nm.

Rheology of mixed solutions of sulfonated methyl esters and betaine in relation to the growth of giant micelles and shampoo applications.

This is a review article on the rheological properties of mixed solutions of sulfonated methyl esters (SME) and cocamidopropyl betaine (CAPB), which are related to the synergistic growth of giant micelles. Effects of additives, such as fatty alcohols, cocamide monoethanolamine (CMEA) and salt, which are expected to boost the growth of wormlike micelles, are studied. We report and systematize the most significant observed effects with an emphasis on the interpretation at molecular level and understanding the rheological behavior of these systems.

The structure of alkyl ester sulfonate surfactant micelles: The impact of different valence electrolytes and surfactant structure on micelle growth.

The ester sulfonate anionic surfactants are a potentially valuable class of sustainable surfactants. The micellar growth, associated rheological changes, and the onset of precipitation are important consequences of the addition of electrolyte and especially multi-valent electrolytes in anionic surfactants. Small angle neutron scattering, SANS, has been used to investigate the self-assembly and the impact of different valence electrolytes on the self-assembly of a range of ester sulfonate surfactants with subtly different molecular structures.

Oral Supplementation of Tocotrienol-Rich Fraction Alleviates Severity of Ulcerative Colitis in Mice.

Ulcerative colitis (UC) is characterized by damaged colonic mucosa and submucosa layers that are caused by excessive inflammatory reactions and oxidative stress. This study aimed to examine the use of tocotrienol-rich fraction (TRF) in mitigating damages caused by UC on the colon epithelium. Dextran sulfate sodium (DSS)-induced UC mice were treated with vehicle control, TRF, alpha-tocopherol (αTP) and 5-aminosalicylic acid (5-ASA).

Impact of molecular structure, headgroup and alkyl chain geometry, on the adsorption of the anionic ester sulfonate surfactants at the air-solution interface, in the presence and absence of electrolyte.

The transition from monolayer to multilayer adsorption at the air-water interface in the presence of multivalent counterions has been demonstrated for a limited range of anionic surfactants which exhibit increased tolerance to precipitation in the presence of multivalent counterions. Understanding the role of molecular structure in determining the transition to surface ordering is an important aspect of the phenomenon. The focus of the paper is on the alkyl ester sulfonate, AES, surfactants; a promising group of anionic surfactants, with the potential for improved performance and biocompatibility.

Properties of the micelles of sulfonated methyl esters determined from the stepwise thinning of foam films and by rheological measurements.

Hypotheses: The micellar solutions of sulfonated methyl esters (SME) are expected to form stratifying foam films that exhibit stepwise thinning. From the height of the steps, which are engendered by micellar layers confined in the films, we could determine the micelle aggregation number, surface electric potential, and ionization degree. Moreover, addition of the zwitterionic surfactant cocamidopropyl betaine (CAPB) is expected to transform the small spherical micelles of SME into giant wormlike aggregates.

The performance of surfactant mixtures at low temperatures.

Optimising detergency at lower temperatures is of increasing interest due to environmental and economic factors, and requires a greater understanding of the effects of temperature on the adsorption of surfactant mixtures at interfaces. The adsorption properties of surfactant mixtures and biosurfactant/surfactant mixtures have been studied at room temperatures and at temperatures below ambient using surface tension and neutron reflectivity measurements. For the ternary surfactant mixture of octaethylene monododecyl ether, CE, sodium dodecyl 6-benzene sulfonate, LAS, and sodium dioxyethylene glycol monododecyl sulfate, SLES, the surface tension at the air-water interface increases with decreasing temperature.

The role of competitive counterion adsorption on the electrolyte induced surface ordering in methyl ester sulfonate surfactants at the air-water interface.

The strong binding of Al trivalent counterions to the anionic surfactants sodium polyethylene glycol monoalkyl ether sulfate and α-methyl ester sulfonate results in surface multilayer formation at the air-water interface. In contrast the divalent and monovalent counterions Ca and Na result only in monolayer adsorption. Competitive counterion adsorption has been extensively studied in the context of surfactant precipitation and re-dissolution, but remains an important feature in understanding this surface ordering and how it can be manipulated.

Saponin Adsorption at the Air-Water Interface-Neutron Reflectivity and Surface Tension Study.

Saponins are a large group of glycosides present in many plant species. They exhibit high surface activity, which arises from a hydrophobic scaffold of triterpenoid or steroid groups and attached hydrophilic saccharide chains. The diversity of molecular structures, present in various plants, gives rise to a rich variety of physicochemical properties and biological activity and results in a wide range of applications in foods, cosmetics, medicine, and several other industrial sectors.

Membrane-lytic actions of sulphonated methyl ester surfactants and implications to bactericidal effect and cytotoxicity.

Surfactants are multifunctional molecules widely used in personal care and healthcare formulations to cleanse, help disperse active ingredients (e.g., forming emulsions) and stabilise products.

Adsorption and self-assembly in methyl ester sulfonate surfactants, their eutectic mixtures and the role of electrolyte.

The α-methyl ester sulfonate, MES, anionic surfactants are a potentially important class of sustainable surfactants for a wide range of applications. The eutectic-like Kraft point minimum in the C and C-MES mixtures is an important feature of that potential. Understanding their individual adsorption properties and the surface mixing of the eutectic mixtures are key to their wider exploitation.

The impact of electrolyte on the adsorption of the anionic surfactant methyl ester sulfonate at the air-solution interface: Surface multilayer formation.

The methyl ester sulfonates represent a promising group of anionic surfactants which have the potential for improved performance and biocompatibility in a range of applications. Their solution properties, in particular their tolerance to hard water, suggests that surface ordering may occur in the presence of multi-valent counterion. Understanding their adsorption properties in a range of different circumstances is key to the exploitation of their potential.

Adsorption at the Air-Water Interface in Biosurfactant-Surfactant Mixtures: Quantitative Analysis of Adsorption in a Five-Component Mixture.

The composition of the air-water adsorbed layer of a quinary mixture consisting of three conventional surfactants, octaethylene glycol monododecyl ether (CE), dodecane-6-p-sodium benzene sulfonate (LAS6), and diethylene glycol monododecyl ether sodium sulfate (SLES), mixed with two biosurfactants, the rhamnolipids l-rhamnosyl-l-rhamnosyl-β-hydroxydecanoyl-β-hydroxydecanoyl, R2, and l-rhamnosyl-β-hydroxydecanoyl-β-hydroxydecanoyl, R1, has been measured over a range of compositions above the mixed critical micelle concentration. Additional measurements on some of the subsets of ternary and binary mixtures have also been measured by NR. The results have been analyzed using the pseudophase approximation (PPA) in conjunction with an excess free energy, G, that depends on the quadratic and cubic terms in the composition.

Adsorption of Methyl Ester Sulfonate at the Air-Water Interface: Can Limitations in the Application of the Gibbs Equation be Overcome by Computer Purification?

We describe a new laboratory synthesis of the α-methyl ester sulfonates based on direct sulfonation of the methyl ester by SO introduced from the vapor phase. This was used to synthesize a chain deuterated sample of αCMES, which was then used to measure the surface excess of αCMES directly at the air/water interface over a wide range of concentration using neutron reflection. The adsorption isotherm could be fitted to an empirical equation close to a Langmuir isotherm and gave a limiting surface excess of (3.