Description of Ionic Surfactant/Water System by Adjusting Mesoscopic Parameters

Abstract

Dissipative particle dynamics simulations were utilized to simulate a model surfactant solution-air system. Amphiphilic surfactant molecules were modeled as dimers composed of a hydrophilic head and a hydrophobic tail. With a simple model, the influence of conservative interaction parameters on the surfactant's properties, including surfactant efficiency and critical micelle concentration (CMC), was investigated in the present research. It is not the surfactant total concentration, but the bulk concentration, that should be employed to achieve the right surfactant properties. It is found that the adjustment of interaction between water and head or air and tail (a(WH) or a(AT)) will result in the obvious change in surfactant efficiency. The parameter that affects CMC the most significantly is the interaction between water and tail (a(WT)). On the basis of the findings about the relationship between conservative interaction parameters and surfactant behaviors, we varied the interaction parameters and simulated a real ionic surfactant system with different tail lengths.

Surface tension model for surfactant solutions at the critical micelle concentration

“…The results presented in [24] demonstrate sequential transition from the bulk solution of individual surfactant molecules to micelle formation through surfactants monolayer formation at the surface when the concentration of the surfactants in the system gradually increased. The surface tension calculated by Kirkwood-Buff formula from trajectories obtained by DPD method also has a qualitatively correct dependence on the bulk concentration of the surfactant and reflects the micelles formation [24]. However, quantitative calculation of σ cmc currently cannot be obtained by DPD because the interactions used in the DPD are oversimplified.…”

“…The combination of Kirkwood-Buff approach with Dissipative Particle Dynamics (DPD) was utilized in [24] to demonstrate qualitatively behavior of water/surfactants solution. DPD is a coarsegrained Molecular Dynamics approach [22,[24][25][26][27][28][29].…”

“…DPD is a coarsegrained Molecular Dynamics approach [22,[24][25][26][27][28][29]. It enables calculations on relatively long timescales, up to microsecond, due to dramatically reduced number of particles and highly simplified inter-particles interactions.…”

Effect of Sodium Dodecyl Sulfate Adsorption on the Behavior of Water inside Single Walled Carbon Nanotubes with Dissipative Particle Dynamics Simulation

“…Thus, the time scale (τ) in our DPD simulation was 0.044 ns. With respect to the repulsion parameter, we adopted results from published reports for DPD simulations [22,24,[32][33][34]. A summary of all repulsion parameters applied in this manuscript is presented in Table 4.…”

“…A summary of all repulsion parameters applied in this manuscript is presented in Table 4. Note that electrostatic interactions were indirectly added into the DPD algorithm by choosing the repulsion parameters of head groups-water and tail groups-water [33]. In solution, surfactant could agglomerate together to form a micelle.…”