Surface-segment attraction, effect

The Effect of Concentration and Segment/Surface Attraction on the Behavior of Chains Bounded by a Pair of Surfaces... 

To connect the internal latent heat with the intrinsic pressure let us consider the forces to which a molecule of the liquid is subject. As long as it is in the interior of the liquid these are obviously equal in all directions, but the case is different when the molecule approaches the surface nearer than the radius of molecular attraction. Let O (Fig. 4) be such a molecule and describe round it a sphere with the radius C of molecular attraction then only the liquid within that sphere will have any effect on O. In the position shown the molecule is attracted downwards by the liquid contained in the segment ab (equal to AB), as the downward... 

The quality of solvent (i.e., solvent-polymer interactions) can also clearly affect the interaction forces. In a good solvent, polymer segments favor contacts with the solvent. Since the compression of the polymer layer by an approaching surface tends to squeeze out the solvent and force segment-segment interactions, the net result is a repulsion. In contrast, poor solvents produce an opposite effect, and a net attraction is possible for certain range of compression (see Section 13.6b). 

Bridging forces, arising when a polymer binds to both surfaces, usually lead to an attraction at large separations. Bridging is only effective at low surface coverage. Only then do the polymer segments have a chance to find an adsorption site on the opposite surface. 

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