Dynamic interfacial tension in binary systems and spontaneous pulsation of individual drops by their dissolution

Influence of process and formulation parameters on the formation of submicron particles by solvent displacement and emulsification–diffusion methods

“…In fact, according to Ostrovsky and Ostrovsky [108] it has been demonstrated that mass transfer by Marangoni effect could not show total agreement with dependence on Δγ. In these cases, the intensity of the mixing process is also influenced by natural convection and forced mixing [108]. The Rayleigh number (R) describes the natural convection intensity, which is proportional to both the mass transfer coefficient for a stable surface (K D ) and the expression on the right:…”

“…Since a liquid with a high surface tension (aqueous solvent) pulls more strongly on the surrounding liquid than one with a low surface tension (organic solvent), this difference between surface tensions causes interfacial turbulence and thermal inequalities in the system, leading to the continuous formation of eddies of solvent at the interface of both liquids which generates interfacial convective flows. These flows contribute towards renewing the interfacial surface and are capable of sharply increasing the mass-exchange rate between the phases [107,108]. Consequently, violent spreading is observed due to mutual miscibility between the solvents which breaks down the organic phase into small droplets which again break down into smaller droplets and so on until forming "submicron droplets".…”

“…where dρ/dc is the change in density of the aqueous phase with the concentration of organic phase added; ΔC is the change of concentration at the surface of the organic/aqueous phase; D AB is the diffusion coefficient of the organic phase in the aqueous phase and η the organic phase viscosity [108]. As can be seen, the interaction between organic and aqueous phases and mixture density could also influence the efficiency of phase mixing.…”

“…Research by Ostrovsky and Ostrovsky [108] showed that Δγ decreases as the concentration of organic solvent in water increases. This reduces the intensity of the pulsations and, as a consequence, the Marangoni effect.…”

“…For instance, Miller referred to Rayleigh-Taylor instability or the phase fragmentation phenomena governed by the drop curvature of the dispersed phase [105]. In fact, according to Ostrovsky and Ostrovsky [108] it has been demonstrated that mass transfer by Marangoni effect could not show total agreement with dependence on Δγ. In these cases, the intensity of the mixing process is also influenced by natural convection and forced mixing [108].…”