Numerical simulations of the effect of ionic surfactant/polymer on oil–water interface using dissipative particle dynamics

Abstract

Effects of the ionic surfactant (cetyltrimethylammonium bromide) and polymer (styrene-maleic acid copolymers) on the oil/water interface are studied using dissipative particle dynamics at the mesoscopic scale. Effects of the water content on equilibrated morphology of the oil/water emulsion are studied with the help of ionic surfactant. In addition, oil/water emulsion has the patterns of the compound emulsifier at the very low and very high water content. The interfacial tension increases, reaches maximum, and then decreases with an increase of water content. Both experiments and simulations show that the inorganic salts can improve the interfacial efficiency of the ionic surfactants, and lower the interfacial tension. The influence of polymer number is studied on their ability to reduce interfacial tension. The distributions of interfacial tension and mean interfacial density are predicted. The lower the interfacial tension and faster oil coalescence are, the more polymers are. In addition, the influence of the polymer on the surfactant aggregation behavior of the oil-water interface is discussed.

Effects of Salt and Surfactant on Interfacial Characteristics of Water/Oil Systems: Molecular Dynamic Simulations and Dissipative Particle Dynamics

“…Unlike SCFT, DPD can describe the IFT variation and aggregation of surfactants into spherical micelles near the CMC. Wang et al investigated the behaviors of water/surfactant/oil systems through multiple DPD simulations considering different ionic/nonionic surfactant molecules and different combinations of these molecules. − Effects of cationic (cetyltrimethylammonium bromide, CTAB), anionic (sodium dodecyl benzene sulfonate, SDBS), and nonionic (polyethylene oxide and polypropylene oxide in a linear form, PEO-PPO-PEO) surfactant molecules were considered at various temperatures, surfactant concentrations, and water/oil ratios. They found that increasing temperature causes the IFT to decrease and the radius of gyration to increase in all cases.…”

Combined effects of polymer/surfactant mixtures on dynamic interfacial properties

“…A pendant drop interfacial rheometer was chosen because it harmonically increases and decreases the interfacial area. The following equation describes the harmonic expansion/compression of the liquid interfacial area A with the angular frequency ω and the oscillation of the IFT γ , because of the adsorption layer at the interface being expanded and compressed:…”

“…If the interface layer is viscoelastic, it can be described in the complex form where E′ is the storage modulus and E ′′ is the loss modulus …”

“…A rising drop of heptane was vertically maintained in a thermostated cell full of the aqueous phase using a microsyringe. An image of the drop was taken with a charge‐coupled device camera and digitized . The pendant drop interfacial rheometer periodically measured changes of the drop interfacial area and then determined the sinusoidal changes of the drop interfacial area.…”

“…Equilibrium IFTs have been obtained after a sufficiently long adsorption time to reach plateau values. The interfacial dilational viscoelasticity was measured after reaching equilibrium IFT value at a frequency of 0.1 Hz, which is based on sinusoidal changes of the drop interfacial area, provided that the drop interfacial area change is less than 5% and the drop volume is constant for a long period of time …”