Conformations of a polyelectrolyte chain

A self-consistent variational theory for obtaining the size of a polyelectrolyte chain, R, for arbitrary values of the experimentally controllable parameters characterizing a dilute polyelectrolyte solution is derived using the Edwards model for the chain. In appropriate limits the theory reproduces the scaling behavior in a good solvent, a Θ solvent, and a poor solvent. In particular, we show that, if the solvent is sufficiently poor, the size of the polyelectrolyte chain changes abruptly from a swollen state (R∼${\mathit{bN}}^{3/5}$, N is the number of monomers, b is the monomer size) to a globule state (R∼${\mathit{bN}}^{1/3}$) or from a rodlike configuration (R∼Na) to a globule depending on the limiting values of the salt concentration.