We illustrate the effects of dielectric inhomogeneity on the statistical Polyelectrolytes in solution form an important class of macromolecules that are essential in biology and colloidal science, and have been the subject of intensive theoretical and experimental investigations; see ref. 1 for an extensive review of the issues and relevant literature.The standard model for polyelectrolytes in solution typically assumes some chain models for the polymer, such as the beadspring model, 2 lattice model 3 or Gaussian thread model, 4 in implicit solvents. The charges are taken to interact with Coulomb potential in a dielectric medium, with a uniform dielectric constant of the solvent. Some studies account for the solvent explicitly by treating the solvent molecules as LennardJones particles, 5 but the electrostatic interactions are still included at the level of dielectric continuum with a uniform dielectric constant. In reality, however, the typically hydrophobic polymer backbone can have a very different dielectric response than the solvent, which will alter the electrostatic interactions between the charges in the vicinity of the polymer. While the use of a uniform dielectric constant of the solvent can be rationalized when the segmental concentration of the polymer is low, as in the case of dilute, good-solvent conditions, it can no longer be justied when the polymer concentration becomes high. The latter can correspond either to a concentrated bulk solution, or to a single polymer in or near a collapsed or partially collapsed state. Even under dilute, goodsolvent conditions, the degree of charge condensation can be affected by the local dielectric response of the polymer backbone.
6In this communication, we demonstrate the importance of including the dielectric inhomogeneity in modeling polyelectrolytes in solution by considering a single polyelectrolyte chain in solvent with no added salt. The decrease of the local dielectric response in the vicinity of the polymer leads to two effects: rst, it alters (strengthens) the Coulomb interactions between the charged species, and second, it expels the counterions from the polymer-rich regions due to the unfavorable solvation energy. The combination of these two effects substantially inuences the chain conformation and degree of charge condensation. For example, we show that upon decreasing the dielectric constant of the polymer backbone from that of the solvent, a collapsed polyelectrolyte chain can turn into the coil state.For computational efficiency, we adopt a lattice formulation by combining the bond uctuation model (BFM), 7,8 a standard lattice Monte Carlo method for polymers, 9 with a local algorithm developed by Maggs et al.10-12 for computing the electrostatic interactions. This algorithm requires a computational effort of order N, 10 and can be directly implemented on a lattice, making it naturally compatible with lattice models of polymers. Furthermore, the dielectric difference between the polymer and the solvent can be easily incorporated. Thus, the la...