Adsorption at liquid interfaces

Thermodynamics of adsorption at liquid interfaces has been well established [22-24]. Of particular interest in view of biochemical and pharmaceutical applications is the adsorption of ionic substances, as many of biologically active compounds are ionic under the physiological conditions. For studying the adsorption of ionic components at the liquid-liquid interface, the polarized liquid-liquid interface is advantageous in that the adsorption of ionic components can be examined by strictly controlling the electrical state of the interface, which is in contrast to the adsorption studies at the air-water or nonpolar oil-water interfaces [25]. 

Dynamics of Adsorption at Liquid Interfaces Theory, Experiment, Application by S.S. Dukhin, G. Kretzschmar and R. Miller... 

Adamson, A. W., Physical Chemistry of Surfaces, 5th ed., Wiley, New York, 1990. (Graduate level. A more extended and somewhat more advanced treatment of adsorption at liquid interfaces in Chapter 4 and adsorption at solid-liquid interfaces in Chapter 11.)... 

Dickinson, E. Protein Adsorption at Liquid Interfaces and the Relationship to Foam Stability in Foams Physics, Chemistry, and Structure, Wilson, A.J. (Ed.), Springer-Verlag London, 1989, pp. 39-53. 

Davies, J.T. and Rideal, E.K. Adsorption at Liquid Interfaces Interfacial Phenomena. Academic Press New York, 1961, pp. 154—216. 

Table 1.5. Extension of some quasi-static techniques to obtain time-dependent surface and interfacial tensions for (surfactant) solutions. ) Modified after S.S. Dukhin, G. Kretzschmar and R. Miller, Dynamics of Adsorption at Liquid Interfaces (Elsevier, 1995), 142.

Bashforth F and Adams JC (1883) An attempt to test the capillary action, Cambridge University Press and Deighton Bell Co., Cambridge Chen P, Kwork DY, Prokop RM, del-Rio 01, Susnar SS and Neumann AW (1998) Axisymmetric drop shape analysis (ADSA) and its applications , in Drops and bubbles in interfacial research, D. Moebius and R. Miller Eds., Studies in Interface Science Series, Vol. 6, Elsevier, Amsterdam Dukhin SS, Kretzschmar G and R. Miller R (1995) Dynamic of adsorption at liquid interfaces. Theory, experiments, applications, D. Moebius and R. Miller Eds., Studies in Interface Science Series, Vol. 1, Elsevier, Amsterdam Joos P (1999) Dynamic Surface Phenomena, VSP, Utrecht, 1999 Kovalchuk VI, Zholkovskij EK, Kragel J, Miller R, Fainerman VB, Wiistneck R, Loglio G and Dukhin SS (2000) Bubble Oscillations in a Closed Cell. J Colloid Interface Sci 224 245-254... 

Dukhin, S.S., Kretzschmar, G., and Miller, R., Dynamics of Adsorption at Liquid Interfaces, in Studies in Surface Science , vol. 1, D. Mobius and R. Miller (Editors), Elsevier, Amsterdam, 1995... 

The aim of this chapter is to present the fundamentals of adsorption at liquid interfaces and a selection of techniques, for their experimental investigation. The chapter will summarise the theoretical models that describe the dynamics of adsorption of surfactants, surfactant mixtures, polymers and polymer/surfactant mixtures. Besides analytical solutions, which are in part very complex and difficult to apply, approximate and asymptotic solutions are given and their range of application is demonstrated. For methods like the dynamic drop volume method, the maximum bubble pressure method, and harmonic or transient relaxation methods, specific initial and boundary conditions have to be considered in the theories. The chapter will end with the description of the background of several experimental technique and the discussion of data obtained with different methods. 

There are two general ideas to describe the dynamics of adsorption at liquid interfaces. The diffusion controlled model assumes the diffusional transport of interfacially active molecules from the bulk to the interface to be the rate-controlling process, while the so-called kinetic controlled model is based on transfer mechanisms of molecules from the solution to the adsorbed state and vice versa. A schematic picture of the interfacial region is shown in Fig. 4.1. showing the different contributions, transport in the bulk and the transfer process. 

There are many other experimental method for studying the dynamics of adsorption at liquid interfaces. First of all, many other techniques exist to measure dynamic surface and interfacial tensions. Only a subjective selection of some more experimental developments are given in the following section. Moreover, other than surface and interfacial techniques are discussed in this chapter too, such as radiotracer, ellipsometer, electric potential, and spectroscopic methods. 

Dukhin, S.S., Kretzschmar, G. and Miller, R., Dynamics of Adsorption at Liquid Interfaces, Elsevier, Amsterdam 1995. 

For reviews of both experiments and theory see Borwankar RP, Wasan DT (1988) Chem Eng Sci 43 1323 Miller R, Kretzschmar G (1991) Adv Colloid Interface Sci 37 97 Dukhin SS, Kretzschmar G, Miller R (1995) In Mobius D, Miller R (eds) Dynamics of Adsorption at Liquid Interfaces Theory, Ex-... 

It was pointed out earlier that surfactant adsorption at liquid interfaces can influence emulsion stability by lowering interfacial tension, increasing surface elasticity, increasing electric double layer repulsion (ionic surfactants), lowering the effeetive Hamaker constant, and possibly increasing surface viscosity. Surfactant can determine the arrangement of the phases in an emulsion, that is, which phase will form the dispersed versus continuous phase. We will briefly summarize several rules of thumb. A very qualitative rule of emulsion type, Bancroft s rule, states that if a... 

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