This paper has been submitted at Nov 4th, 1996, for publication in a
scientific journal and is now subject to the reviewing process.
You may ask for a hardcopy with the complete manuscript, which contains all figures and all
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This is the 3rd revised version.
Dr. Bernhard Wessling
Zipperling Kessler / Ormecon Chemie
D-22949 Ammersbek
Conductive Polymer / Solvent Systems: Solutions or Dispersions?
2.4 Dispersions
We will now briefly discuss some basic thermodynamic aspects of dispersions in order to approach the hypothesis that PAni (EB and ES) might only form dispersions in appropriate solvents.
In contrast to solutions, dispersions are systems in a state far from equilibrium. It is always necessary to invest a certain significant amount of energy to create dispersions. Under isothermal conditions the necessary energy is equal to the energy needed for creating new surfaces from the bulk (of both components, the dispersed phase and the dispersing medium). This energy is
with 
0 being the surface tension and A the surface.
If at all happening, a potential increase of entropy is orders of magnitude less compared to the one in solutions, because the number of particles in dispersion is much less than the number of molecules in solution for a comparable concentration. There are arguments[13] according to which no entropy increase is occurring during dispersion, but in contrast, even a significant decrease is reasonable to assume.
In other words: the amount of energy needed to create dispersions is at least equivalent to the increase in surface energy of the system. There are also strong arguments for the statement, that no dispersion will occur exergonically (or: deliberately). We have to stir, more or less vigorously, or to shuffle[14], for creation of new surfaces/interfaces. (This does not necessarily imply, that dispersions are unstable; there are clear mechanistic and thermodynamical reasons for the fact that many dispersions can be stable over very long time, if not "forever".)
