In this chapter we consider the properties of solid/polymer solution interfaces for which χs < χsc. As indicated in sec. 2.8, in this situation polymer coils tend to be repelled from the solid surface, for entropic reasons. A quantitative description of this effect has been presented in secs. 126.96.36.199 and 4. It gives rise to a segment volume fraction profile of the form indicated in fig. 2.8.1 and reproduced here as fig. 10.1.1. Here there is negative excess adsorption of segments in the interfacial region. The phenomenon has also been termed depletion. This term was first coined by Joanny et al.  in the context of the flocculation effect that may occur when non-adsorbing polymer is added to dispersions of colloidal particles. The consequences of depletion for the free energy of interaction between particles will be discussed in more detail in sec.11.3.
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