Surface-segment interaction

Even complicated, charged macromolecules like proteins can be succesfully displaced. As an example we give in Figure 6 the displacement isotherm for human plasma albumin from silica by morpholine (21). Of course, in this case where charge effects and a variety of segment/surface interactions play a role, our simple Equation 5 does not apply. Nevertheless, for practical work it is important to realize that most macromolecules, often thought to be irreversibly adsorbed, can be removed completely from the adsorbent surface by the concerted action of a large number of small molecules. 

Further, for planes 1 and M the segment/surface interactions will necessitate the introduction of the Boltzmann factor in the probability equation. Thus ... 

Fig. 3.36 Segment density profiles from a Monte Carlo computer simulation of adsorption of a BAB triblock at a planar interface, where the hydrophobic B block is preferentially adsorbed (Balazs and Lewandowski 1990). Profiles are plotted for different A segment-surface interaction parameters, AS, with Xas = 0 and a chain length - 30 units.

We wish to report some work on the adsorption of acid and alkali-precursor gelatins, the water-soluble products of collagen. The study of both types allowed us to determine whether the differences exhibited by the two kinds in solution are reflected in the adsorbed state, and offers some insight into the state of flexible molecules at interfaces. The use of two dissimilar adsorbents, glass and stainless steel powders, should yield information on segment-surface interactions during the adsorption process. Some effects of added calcium ions were also studied since the Ca-ions of hydroxyapatite in bone and teeth are intimately related to collagen. 

Because of slower motions of polymer chains in adsorbed layers compared to that of small molecules, adsorption isotherms might also reflect slow equilibration of polymer chains at the surface, especially for longer polymer chains and stronger segment-surface interactions. 

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