Surfactants and Wetting on Polar Surfaces

When surfactants are added into the equation, wetting can become even more complicated because of the many specific interactions that can occur between surfactant and solid, surfactant and water, and surfactant and oil. 

The exact effect of a given surfactant on a system will be determined by the degree and mode (i.e., orientation) of its adsorption at the various interfaces, and the reversibility of that adsorption. Some of the factors that affect those variables include 

The degree and nature of the polarity of the surface (dipole moment, polarizability, etc.) 

The presence and nature of surface charges (charge density, degree of ionization, nature of charge-determining ions, etc.) 

The pH and ionic strength of the aqueous solution, both of which may affect charge density, ionization of the surface, ionization of the surfactant, and other variables. 

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