Thermodynamic interaction between polymer and surface

The adsorption of polymers from solutions strongly depends on the thermodynamic quality of solvent and the interaction energy between polymer and surface. All theories of adsorption include the thermodynamic parameter of interaction of the Flory-Huggins theory %i2. The thermodynamic interaction between polymer and solvent determines the conformation of macromolecules in solutions and thus the conditions of its interaction with the surface. The interaction between polymer and surface is characterized by the parameter of thermodynamic interaction, which was introduced by Silberberg, using the model of quasi-crystalline lattice of the surface layer, describing the properties of polymer solutions. This parameter may be determined as follows  

The preferential adsorption of displacer is characterized by the negative value of% In the three-component system, the adsorption may be represented as an exchange process between each of the three-component pairs polymer-solvent, polymer-displacer, and solvent-displacer. The free energy change of all three processes, which may be expressed by three %s and three Xs parameters for six concentrations in the surface layers and in the bulk solution, must be zero. In order to describe the equilibrium in a three-component solution, it is sufficient to calculate the free energy of two exchange processes in which all three components participate. 

The experimental verification was presented for the adsorption of polyvinylpyrrolidone on silica,and adsorption of PMMA on fumed silica. The theory developed gives the possibility of experimental evaluation of the energetic factors and their role in adsorption. 

Another experimental method of estimation of the energetics of adsorption is based on direct calorimetric determination of heat of adsorption. The integral heat of adsorption is determined from the relation  

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