Star polymers conformation, dilute solution

As discussed above, the strong correlation of the counterions to the macroions leads to a remarkable osmotic pressure within the macroions, in this case the polyelectrolyte stars. To decrease this pressure, the arms of the polyelectrolyte stars are strongly stretched in dilute solution in the absence of added salt. However, if salt is added to the solution, the osmotic pressure difference will be reduced greatly, and the stretching of the arms will be diminished dramatically. Under these conditions the size and conformation of the polyelectrolyte stars will be comparable to the solution structure of uncharged star polymers. 

The first theories that implemented a proper balance of intramolecular interactions and conformational elasticity of the branches were developed by Daoud and Cotton [21] and by Zhulina and Birshtein [22-24]. These theories use scaling concepts (the blob model), originally developed by de Gennes and Alexander to describe the structure of semidilute polymer solutions [64] and planar polymer brushes [65, 66]. Here, the monomer-monomer interactions were incorporated on the level of binary or ternary contacts (corresponding to good and theta-solvent conditions, respectively), and both dilute and semidilute solutions of star polymers were considered. Depending on the solvent quality and the intrinsic stiffness of the arms, the branches of a star could be locally swollen, or exhibit Gaussian statistics [22-24]. 

---