Impact of Micelles on Adsorption Kinetics

The maximum bubble pressure method (M BPM) has been demonstrated as suitable for studies of micellar solutions. Various aspects of this methodology have been reviewed in detail [35,40], including the physical processes taking place during the formation and growth of a bubble at the tip of a capillary and its separation, the 

We report here on dynamic surface tensions recently obtained from BPA (from SINTERFACE Technologies, Berlin, Germany) measurements on micellar solutions of C 4EOg. 

In Ref. [42] it was shovm that at short times and under the assumption 1 (kf = kr) the following equation (obtained in Ref. [17])  

data for C14EO8 from Ref [42], as well as from Ref. [12] for this surfactant, show faster dissociation kinetics of micelles at concentration above 20 x CMC. To reach agreement between theory and experiment at higher concentrations, kf has to be increased by approximately 100 times. 

Notably, an expression quite similar to Equation 13.3 for low surface pressures O follows from the model that accounts for the influence of micelles (assuming fast micelle disintegrationldnetics) on the effective monomer diffusion coefficient [25,42]  

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The aim of this chapter is to present the fundamentals of adsorption kinetics of surfactants at liquid interfaces. Theoretical models will be summarised to describe the process of adsorption of surfactants and surfactant mixtures. As analytical solutions are either scarcely available or very complex and difficult to apply, also approximate and asymptotic solutions are given and their ranges of application demonstrated. For particular experimental methods specific initial and boundary conditions have to be considered in these theories. In particular for relaxation theories the experimental conditions have to be met in order to quantitatively understand the obtained results. In respect to micellar solutions and the impact of micelles on the adsorption layer dynamics a detailed description on the theoretical basis as well as a selection of representative experiments will follow in Chapter 5. 

There are various direct measurements of micellar solutions giving access to the dynamics rate constants - mainly based on disturbance of the equilibrium state by imposing various types of perturbations, such as stop flow, ultrasound, temperature and pressure jump [14,15[. This aspect is also not further elaborated here we focus instead on the impact of micellar kinetics on interfacial properties, to demonstrate that tensiometry and dilational rheology are suitable methods to probe the impact of micellar dynamics. The first work on this subject was published by Lucassen already in 1975 [16[ and he showed that the presence of micelles in the bulk have a measurable impact on the adsorption kinetics, and hence on the dilational elasticity, when measured by a longitudinal wave damping technique. Subsequent work demonstrated the effect of micellar dynamics on non-equilibrium interfacial properties [17-29]. The physical idea of the impact of micellar dynamics on the dynamic properties of interfacial layers can be easily understood from the scheme given in Figure 13.1. 

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