Surface dilational rheological properties in the nonlinear domain

Phase inversion emulsification: Current understanding and applications

“…Such kinetic stability can also be achieved by exploiting surfactants, which are amphiphilic molecules stabilizing droplets by lowering interfacial tension and eliciting Marangoni stresses [6]. The role of surfactants and amphiphiles in general in lowering interfacial tension [7][8][9][10][11], their adsorption behavior as well as the interface behavior both in static and dynamic conditions [12][13][14][15][16][17][18][19][20][21][22][23][24][25] have been widely studied. Emulsions having fine droplet size are more stable against phase separation and widely exploited in application also due to their capability to incorporate hydrophilic or hydrophobic species.…”

Adsorption Kinetics of a Cationic Surfactant Bearing a Two-Charged Head at the Air-Water Interface

“…The reorganization may include the formation of aggregates at the interface, condensation of counter-ions onto those aggregates, and further surfactant adsorption, as well as phase transitions [26,30]. For the surfactant concentrations above the cmc, some of the processes observed could be related to the presence of micelles and their dynamics (adsorption-desorption, aggregation-disaggregation [27,28]). The redistribution of charges within the interfacial region, as observed in the surface potential experiments, seems to be responsible for the existence of the intermediate relaxations, well-described by exponentials, which are observed on the dynamic surface tension curves.…”

“…We cannot use the previous analysis for surfactant concentrations above the cmc, in this case the adsorption-desorption and aggregation-disaggregation of micelles [27,28] could play a role in the observed dynamics both in γ(t) and ϕ(t). The fact that the dynamics of surfactant adsorption at short times follow an exponential relaxation (see insets on Figure 5) could indicate that we are not accessing times short enough to see the diffusion-limited adsorption step.…”

Effect of Amplitude on the Surface Dilational Visco-Elasticity of Protein Solutions

“…In some cases [12,13], the response is analyzed in more details with account for any non-linear terms of the visco-elasticity. For a quantitative determination of the degree of distortion of the harmonical signal due to non-linear effects one usually uses the total harmonic distortion (THD) index [17,18]. The THD index shows the relative contribution of higher harmonics to the signal as compared to the contribution at the fundamental frequency.…”