Polymer-Induced Forces in Solutions

After discussing the steric repulsion between tethered polymer brushes in a good solvent, let us turn to the more general situation. We consider dispersed particles in a solution of chemically homogeneous polymers, also called homopolymers. Four major factors determine the force between particles in polymer solutions (1) the quality of the solvent, (2) the amount of polymer adsorbed and the way it is adsorbed, (3) the time allowed for the polymer to adsorb and rearrange at the surfaces, let us call it the incubation time, and (4) the time during which two 

Bridging attraction Intersegment attraction Phase separation 

In bad solvent, the polymer-coated surfaces attract each other [1386, 1387]. One reason is the absence of steric repulsion. Van der Waals forces can become dominant again and lead to aggregation. Napper [1311] formulated the rule of thumb that the onset of dispersion flocculation coincides with the creation of conditions in the solvent medium. Exceptions to this rule are encountered when either the polymeric stabilizers are very short or the particles become very small. In addition to van der Waals forces, the polymer itself induces attraction. In a bad solvent, the polymer usually has a strong tendency to adsorb to any surface available. For that reason, we do not have to distinguish all possible cases. Attraction between surfaces is due to intersegment forces. The intersegment force is caused by the direct interaction between segments of polymers with each other. Since in a bad solvent the interaction 

One might think that the long incubation time is due to a slow diffusion of polymer toward the surface. To demonstrate that this is not the case, we estimate the time 

We consider the simple case of diffudon limited adsorption. Diffusion is described by Pick s law. For diffusion toward an infinitely extending plane, we only need to consider the dimension normal to the surface due to symmetry. In a direction x normal to the surface. Pick s law is 

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