The Characteristic Curvature (Cc) of Ionic Surfactants Assessed via Small-Angle X-ray Scattering.

The characteristic curvature (Cc), within the hydrophilic-lipophilic difference + net () - average () curvature (HLD-NAC) framework, is the dimensionless net curvature, -· ( is the surfactant's tail length parameter), that a surfactant acquires at the characteristic condition ( = 25 °C, no added cosurfactants, oil with an equivalent alkane carbon number (EACN) of zero and for ionic surfactants, a total salinity () of 1 g NaCl/100 mL). A recent article demonstrated the validity of the Cc concept, where was assessed via oil and water solubilization radii. Here, we assess from the characteristic length (ξ) obtained from the analysis of SAXS profiles of microemulsions produced at semicharacteristic conditions (characteristic condition but varying ).

HLD-NAC design and evaluation of a fully dilutable lecithin-linker SMEDDS for ibuprofen.

Lecithin-linker microemulsions have been previously proposed as a platform for designing a fully dilutable self-microemulsifying drug delivery system (SMEDDS). This SMEDDS formulation, composed of ethyl caprate (oil), lecithin (Le), glycerol monooleate (lipophilic linker, LL) and polyglycerol caprylate (hydrophilic linker, HL), produced a ternary phase diagram (TPD) that had a fully dilutable path suitable for oral drug delivery. However, introducing ibuprofen as an active pharmaceutical ingredient (API) resulted in TPD phase boundaries that eliminated the fully dilutable path.

Separation of Emulsions with Fibrous Filter-Coalescers.

During froth treatment, a water-in-diluted bitumen emulsion is obtained. The emulsified water contains chloride ions that form hydrochloric acid in downstream oil processing, leading to catalyst deactivation and equipment corrosion. Emulsified water, drops smaller than 10 μm, cannot be effectively removed by gravity settling and centrifugation to below 2 wt %.

Predicting the effect of additives on wormlike micelle and liquid crystal formation and rheology with phase inversion phenomena.

Hypothesis: Surfactant-based viscoelastic fluids are used in consumer products such as body wash, cosmetics, and in hydraulic fracturing fluids to suspend proppant, among others. The solubilization of oil within these fluids changes the curvature of the surfactant and their nanostructure and rheological properties. The curvature-based hydrophilic-lipophilic-difference + net-average-curvature (HLD-NAC) framework may be able to quantify curvature changes and predict the formulation conditions required to obtain viscoelasticity.

Formulating and Retaining the Structure of Polymerized Surfactant Phases Using a Microemulsion Curvature Framework.

Nanostructured polymers contain features smaller than 100 nm that are useful in a wide range of areas, including photonics, biomedical materials, and environmental applications. Out of the myriad of nanostructured polymers, surfactant-templated polymers are versatile because of their ability to have tunable domain sizes, structure, and composition. This work addresses the gap between the formulation with industrial-grade polymerizable surfactants and the final structure of the polymer, using the hydrophilic-lipophilic difference (HLD) and net-average curvature (NAC) frameworks.

Characterizing the Oil-like and Surfactant-like Behavior of Polar Oils.

In this work, a bifunctional model was developed to fit and predict the phase inversion point (PIP) of microemulsions containing polar oils. This model incorporated the hydrophilic-lipophilic difference (HLD) equations, where HLD = 0 at the PIP. The model uses a Langmuir isotherm to account for the interfacial segregation of polar oils as a function of their concentration in the bulk oil phase.

Interfacial Tension of the Water-Diluted Bitumen Interface at High Bitumen Concentrations Measured Using a Microfluidic Technique.

The interfacial tension (IFT) is a critical parameter to inform our understanding of the phenomena of drop breakup and droplet-droplet coalescence in sheared water-in-diluted bitumen (dilbit) emulsions. A microfluidic extensional flow device (MEFD) was used to determine the IFT of the dilbit-water emulsion system for bitumen concentrations of 33%, 50%, and 67% by weight (solvent to bitumen ratio (S/B) = 2, 1, and 0.5, respectively) and two different pH values of water: 8.

Solid-Liquid-Liquid Wettability of Surfactant-Oil-Water Systems and Its Prediction around the Phase Inversion Point.

Surfactant-oil-water (SOW) systems are important for numerous applications, including hard surface cleaning, detergency, and enhanced oil-recovery applications. There is limited literature on the wettability of solid-liquid-liquid (SLL) systems around the surfactant phase inversion point (PIP), and the few references that exist point to wettability inversion accompanying the microemulsion (μE) phase inversion. Despite the significance of this phenomenon and the extreme changes in contact angles, there are no models to predict SLL wettability as a function of proximity to the PIP.

Oil-induced formation of branched wormlike micelles in an alcohol propoxysulfate extended surfactant system.

The addition of oil to an extended surfactant-water system (sodium tetrapropylene glycol (2-ethyl)octyl ether sulfate, CPOSONa) induces the elongation of spherical micelles into oil-swollen branched wormlike micelles (WLMs) near the phase inversion point of the surfactant-oil-water (SOW) system. The hydrophilic-lipophilic-difference (HLD) framework, which has been associated with surfactant curvature, was successfully used to predict the conditions under which WLMs are produced for both polar and non-polar oils. At HLD = 0, the formation of low-curvature surfactant structures including WLMs and liquid crystals are favored in water-rich systems.

Risk Factors for Unfavorable Outcomes in Surgically Treated Brainstem Cavernous Malformations.

Objective: Brainstem cavernous malformations (BSCMs) account for up to 18% of all intracranial cavernous malformations. Due to their complex anatomic location, they represent a significant challenge for neurosurgeons. As such, the identification of risk factors associated with negative outcomes is of significant importance.

Acid-Base Polymeric Foams for the Adsorption of Micro-oil Droplets from Industrial Effluents.

Separation of toxic organic pollutants from industrial effluents is a great environmental challenge. Herein, an acid-base engineered foam is employed for separation of micro-oil droplets from an aqueous solution. In acidic or basic environments, acid-base polymers acquire surface charge due to protonation or dissociation of surface active functional groups.

Design of nonionic micelle-laden polysaccharide hydrogels for controlled delivery of hydrophobic drugs.

The incorporation of micelle self-assembly in hydrogels has been used to produce self-healing materials, materials with tunable mechanical properties, and hydrophilic or hydrophobic drug delivery systems. However, little is known about the connection among formulation - structure - properties (particularly transport) in these systems. This connection is explored in alkyl ethoxylate micelle-laden gellan gum hydrogels used as delivery system for the hydrophobic drug dexamethasone.

Predicting solubilisation features of ternary phase diagrams of fully dilutable lecithin linker microemulsions.

Fully dilutable microemulsions (μEs), used to design self-microemulsifying delivery system (SMEDS), are formulated as concentrate solutions containing oil and surfactants, without water. As water is added to dilute these systems, various μEs are produced (water-swollen reverse micelles, bicontinuous systems, and oil-swollen micelles), without the onset of phase separation. Currently, the formulation dilutable μEs follows a trial and error approach that has had a limited success.

Integrated Free Energy Model (IFEM) for microemulsions.

The Integrated Free Energy Model (IFEM) is a platform used to predict the solubilization of nonpolar oils in nonionic alkyl-polyethylene oxide (C(X)EO(Y)) micelles starting from a free energy balance of costs and gains when surfactants from empty micelles and oil from a continuous oil phase assemble to form an oil-swollen micelle. IFEM considers lipophilic interactions between surfactant tails and oil solubilized in the core of micelles, and the interaction between surfactant tails and the oil solubilized in the surfactant tail domain, as well as oil-oil and surfactant-surfactant tail interactions. Expressions to calculate these lipophilic interactions from van der Waals (VDW) interaction potential were introduced in a previous publication.

The Cloud Point of Alkyl Ethoxylates and Its Prediction with the Hydrophilic-Lipophilic Difference (HLD) Framework.

The hydrophobicity of surfactants has been described through different concepts used to guide the formulation of surfactant-water (SW) and surfactant-oil-water (SOW) systems. An integrated framework of hydrophobicity indicators could provide a complete tool for surfactant characterization, and insights on how their relationship may influence the overall phase behavior of the system. The hydrophilic-lipophilic difference (HLD) and the characteristic curvature (Cc) parameter, included in the HLD, have been shown to correlate with different hydrophobicity indicators including the hydrophilic-lipophilic balance (HLB), packing factor (Pf), phase inversion temperature (PIT), spontaneous curvature (Ho), surfactant partition (K(o-w)), and the critical micelle concentration (CMC).

Van der Waals free energy model for solubilization of oil in micelles.

This work introduces the first of a two part thermodynamic framework to estimate the solubilization of nonpolar oils in micelles conformed by nonionic surfactants with linear alkyl tails, considering their configuration and the molecular properties of the constituents. This first part introduces a formal approach to account for the lipophilic (van der Waals) contributions to the free energy of solubilization in spherical micelles. To this end, this work uses two recently developed integration methods for sphere-shell and cone-shell VDW interactions that allow the calculation of surfactant-oil and surfactant-surfactant interactions that take place within the micelles of the solubilization process studied here.

Lecithin-linker formulations for self-emulsifying delivery of nutraceuticals.

Lecithin-linker microemulsions are formulations produced with soybean lecithin in combination with a highly lipophilic (lipophilic linker) and highly hydrophilic (hydrophilic linkers) surfactant-like additives. In this work, lecithin-linker systems were formulated to produce self-emulsifying delivery systems for β-carotene and β-sitosterol. The concentration of the lipophilic linker, sorbitan monooleate, was adjusted to minimize the formation of liquid crystals.

Formulation design for target delivery of iron nanoparticles to TCE zones.

Nanoparticles of zero-valent iron (NZVI) are effective reducing agents for some dense non-aqueous phase liquid (DNAPL) contaminants such as trichloroethylene (TCE). However, target delivery of iron nanoparticles to DNAPL zones in the aquifer remains an elusive feature for NZVI technologies. This work discusses three strategies to deliver iron nanoparticles to DNAPL zones.

The van der Waals interactions in sphere-shell and cone-shell configurations.

This work introduces two expressions for the integration of the van der Waals interactions in geometries that are relevant to determining oil solubilization in micelles and the interaction among surfactants in micelles. The first integral applies to the interaction between a sphere and a spherical shell that surrounds the sphere. The second integral calculates the interaction between a truncated cone and the rest of a spherical shell that contains the cone.

Lecithin-linker microemulsion gelatin gels for extended drug delivery.

This article introduces the formulation of alcohol-free, lecithin microemulsion-based gels (MBGs) prepared with gelatin as gelling agent. The influence of oil, water, lecithin and hydrophilic and lipophilic additives (linkers) on the rheological properties and appearance of these gels was systematically explored using ternary phase diagrams. Clear MBGs were obtained in regions of single phase microemulsions (μEs) at room temperature.

Effect of surfactant concentration, compression ratio and compression rate on the surface activity and dynamic properties of a lung surfactant.

This paper reports dynamic surface tension experiments of a lung surfactant preparation, BLES, for a wide range of concentrations, compression ratios and compression rates. These experiments were performed using Axisymmetric Drop Shape Analysis-Constrained Sessile Drop (ADSA-CSD). The main purpose of the paper is to interpret the results in terms of physical parameters using the recently developed Compression-Relaxation Model (CRM).

A miniature cell for gas solubility measurements in oils and bitumen.

A miniature cell has been designed and constructed to measure gas solubility in crude oils and bitumen. The cell was made of stainless steel with a total internal volume of 1.835 cc and only an oil sample of 0.

Behavior and properties in aqueous solution of biopolymers isolated from urban refuse.

Acid soluble biopolymeric substances (SBP) were isolated from different urban biowastes comprised of a range of materials available from metropolitan areas. These biowastes provided products with a chemical nature and solubility properties changing over a wide range and, thus, allowed to assess the effect of the variability of the chemical nature on molecular conformation and surface activity in water solution. For this scope, the SBP were characterized for chemical composition and molecular weight (MW) by microanalysis, potentiometric titration, (13)C NMR spectroscopy, and size exclusion chromatography (SEC) coupled with an online multiangle light scattering (MALS) detector.

The hydrophobicity of silicone-based oils and surfactants and their use in reactive microemulsions.

In this work, for the first time, the Hydrophilic-Lipophilic Difference (HLD) framework for microemulsion formulation has been applied to silicone oils and silicone alkyl polyether surfactants. Based on the HLD equations and recently introduced mixing rules, we have quantified the hydrophobicity of the oils according to the equivalent alkane carbon number (EACN). We have found that, in a reference system containing sodium dihexyl sulfosuccinate (SDHS) as the surfactant, 0.