Entropy polymeric surfactant solution

Dilute aqueous polymeric emulsions are commonly stabilized through the use of polymeric surfactants. If the stabilizer is uncharged, the emulsion is stabilized entropieally by segmental exclusion. In most instances, however, stabilization is a by product of coulombic repulsions generated by a polyelectrolyte surfactant. In a few instances the polymer itself is able to act as surfactant. For example, Eudragit RL, a commercially available partially quaternized cationic methacrylate based polymer, is able to form indefinitely stable emulsions in distilled water or buffered saline (141). These emulsions are prepared by adding polymer to boiling solution and are presumably stabilized by concentration of cationic functionality at the particle surface. 

Some differences between BCP/surfactant systems and surfactant/co-surfactant mixtures arise from the large difference in size and from the polymer-specific chain entropy contributions to the free energy of the systems. Moreover, in contrast to simple surfactant-based samples, the polydispersity of the polymer chains is also an important issue for structure formation. Polydispersity might lead to coexistence of different structures (e.g., spheres and worm-like structures) in the same polymer solution. This is due to the fact that small differences in the degree of polymerization of one of the blocks might lead to different packing parameters for a part of the size distribution. 

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