Monodisperse liquid adsorbent

If it were possible to work with monodisperse liquid adsorbent, it would be important and interesting to compare values of thermodynamic properties determined by measurements of different types. Agreement would indicate correctness of the methods and their interpretation. 

If the adsorbent is known to be a monodisperse liquid (9, 14), the thermodynamics of adsorption is also comparatively simple. It is simplified by the fact that we can conceive of the existence of complete equilibrium of the adsorbent in all parts of an adsorption system and can indulge in thermodynamic reasoning without mental reservations concerning slow exchange of adsorbate or adsorbent between particles of different sizes and shapes. 

One of the simplest methods to study adsorption at the oil water interface is to measure the variation of interfacial tension as a function of concentration. If the polymer used for adsorption is monodisperse, then the Gibbs equation (51) may be used to estimate the surface excess. However, if the polymer is polydis-perse, this method will give erroneous values of the surface excess because the larger molecules will tend to adsorb preferentially, and the equation is imable to account for this adsorption behavior. As a result, most of the data available in the literature report the change in the interfacial tension as a function of concentration without attempting to convert it into an adsorbed amoimt. Apart from interfacial tension measurements, other techniques such as total internal reflection fluorescence microscopy (52) and scintillation measurements from radiolabeled polymers (53) have also been used to measure the adsorption at the liquid-liquid interface. 

---