Charged surface, free energy formation

The Use of Positively Charged or Low Surface Free Energy Coatings versus Polymer Brushes in Controlling Biofilm Formation... 

It is well described that materials in contact with biofluids are irmnediately coated with proteins. Protein adsorption is influenced by the underlying substrate surface properties including surface chemistry, charge, and free energy. After cell adhesion on top of this primary protein layer, the formation of secondary protein layers can take place due to nonspecific adsorption of ceU-secreted proteins (Fig. 4.27). 

Roosjen A, Norde W, van der Mei HC, Busscher HJ The use of positively charged or low surface free energy coatings versus polymer brushes in controlling biofilm formation. Prog Colloid Polym Sci 132 138-144, 2006. 

A general prerequisite for the existence of a stable interface between two phases is that the free energy of formation of the interface be positive were it negative or zero, fluctuations would lead to complete dispersion of one phase in another. As implied, thermodynamics constitutes an important discipline within the general subject. It is one in which surface area joins the usual extensive quantities of mass and volume and in which surface tension and surface composition join the usual intensive quantities of pressure, temperature, and bulk composition. The thermodynamic functions of free energy, enthalpy and entropy can be defined for an interface as well as for a bulk portion of matter. Chapters II and ni are based on a rich history of thermodynamic studies of the liquid interface. The phase behavior of liquid films enters in Chapter IV, and the electrical potential and charge are added as thermodynamic variables in Chapter V. 

Since the equations of state of the system are summarized by the curves in Figure 2, all interesting thermodynamic properties of the interface will have a simple representation in such a diagram. We shall consider the free energy of formation of a single charged surface and the interaction free energy due to the overlap of two identical planar double layers. 

For a neutral gas, the adsorption (which is proportional to the free energy of the system, see Eq. (8)) can be calculated easily. For charged particles one should account in the Gibbs adsorption equation for the adsorption of all particles of the system (including those responsible for the charging of the surface [23]). Therefore, one should first identify the mechanism of formation of the double layer. In this case,... 

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