Interfacially-Adsorbed Particles Enhance the Self-Propulsion of Oil Droplets in Aqueous Surfactant

We have demonstrated that adsorption of silica nanoparticles at the interface of a solubilizing oil droplet in surfactant solution can significantly accelerate the droplets’ self-propulsion speed. Using fluorescent particle visualization, we correlated the degree of particle surface coverage on bromodecane droplets to the droplet speed in TX surfactant. Slowest speeds were found at the lowest and highest surface coverages and the fastest speeds were achieved at intermediate surface coverages of about 40%. The particle-assisted propulsion acceleration was further demonstrated in nonionic, anionic, and cationic surfactants and a range of oils with varying solubilization rates. We propose that particles at the droplet interface hinder solubilization by displacing oil-water interfacial area, providing asymmetry in the distribution of oil-filled micelles along the droplet surface and accelerating Marangoni flow. We describe a fluid-mechanical model to rationalize the effect of the particles by considering the effect of a non-symmetrical distribution of solubilized oil at the droplet surface. Approaches by which to modulate the distribution of solubilization across droplet interfaces may provide a facile route to tuning active colloid speeds and dynamics. <br>

Rapid analysis of anionic and cationic surfactants in water by paper spray mass spectrometry

We present the development of PS-MS into an analytical tool for the study of surfactants in water samples. The method has a short analysis time, low solvent consumption, no need for sample pretreatment and simultaneous multi-surfactant detection.

Adsorption of Equimolar Mixtures of Cationic and Anionic Surfactants at the Water/Hexane Interface

In mixed solutions of anionic and cationic surfactants, called catanionics, ion pairs are formed which behave like non-ionic surfactants with a much higher surface activity than the single components. In equimolar mixtures of NaCnSO4 and CmTAB, all surface-active ions are paired. For mixtures with n + m = const, the interfacial properties are rather similar. Catanionics containing one long-chain surfactant and one surfactant with medium chain length exhibit a strong increase in surface activity as compared with the single compounds. In contrast, catanionics of one medium- and one short chain surfactant have a surface activity similar to that of the medium-chain surfactant alone. Both the Frumkin model and the reorientation model describe the experimental equilibrium data equally well, while the adsorption kinetics of the mixed medium- and short-chain surfactants can be well described only with the reorientation model.

Interfacially-Adsorbed Particles Enhance the Self-Propulsion of Oil Droplets in Aqueous Surfactant

We have demonstrated that adsorption of silica nanoparticles at the interface of a solubilizing oil droplet in surfactant solution can significantly accelerate the droplets’ self-propulsion speed. Using fluorescent particle visualization, we correlated the degree of particle surface coverage on bromodecane droplets to the droplet speed in TX surfactant. Slowest speeds were found at the lowest and highest surface coverages and the fastest speeds were achieved at intermediate surface coverages of about 40%. The particle-assisted propulsion acceleration was further demonstrated in nonionic, anionic, and cationic surfactants and a range of oils with varying solubilization rates. We propose that particles at the droplet interface hinder solubilization by displacing oil-water interfacial area, providing asymmetry in the distribution of oil-filled micelles along the droplet surface and accelerating Marangoni flow. We describe a fluid-mechanical model to rationalize the effect of the particles by considering the effect of a non-symmetrical distribution of solubilized oil at the droplet surface. Approaches by which to modulate the distribution of solubilization across droplet interfaces may provide a facile route to tuning active colloid speeds and dynamics. <br>

Interfacially-Adsorbed Particles Enhance the Self-Propulsion of Oil Droplets in Aqueous Surfactant

We have demonstrated that adsorption of silica nanoparticles at the interface of a solubilizing oil droplet in surfactant solution can significantly accelerate the droplets’ self-propulsion speed. Using fluorescent particle visualization, we correlated the degree of particle surface coverage on bromodecane droplets to the droplet speed in TX surfactant. Slowest speeds were found at the lowest and highest surface coverages and the fastest speeds were achieved at intermediate surface coverages of about 40%. The particle-assisted propulsion acceleration was further demonstrated in nonionic, anionic, and cationic surfactants and a range of oils with varying solubilization rates. We propose that particles at the droplet interface hinder solubilization by displacing oil-water interfacial area, providing asymmetry in the distribution of oil-filled micelles along the droplet surface and accelerating Marangoni flow. We describe a fluid-mechanical model to rationalize the effect of the particles by considering the effect of a non-symmetrical distribution of solubilized oil at the droplet surface. Approaches by which to modulate the distribution of solubilization across droplet interfaces may provide a facile route to tuning active colloid speeds and dynamics. <br>

A Short Review on the Effect of Surfactants on the Mechanico-Thermal Properties of Polymer Nanocomposites

The recent growth of nanotechnology consciousness has enhanced the attention of researchers on the utilization of polymer nanocomposites. Nanocomposite have widely been made by using synthetic, natural, biosynthetic, and synthetic biodegradable polymers with nanofillers. Nanofillers are normally modified with surfactants for increasing the mechanico-thermal properties of the nanocomposites. In this short review, two types of polymer nanocomposites modified by surfactants are classified, specifically surfactant-modified inorganic nanofiller/polymer nanocomposites and surfactant-modified organic nanofiller/polymer nanocomposites. Moreover, three types of surfactants, specifically non-ionic, anionic, and cationic surfactants that are frequently used to modify the nanofillers of polymer nanocomposites are also described. The effect of surfactants on mechanico-thermal properties of the nanocomposites is shortly reviewed. This review will capture the interest of polymer composite researchers and encourage the further enhancement of new theories in this research field.