| Abstract
| - The conformational behavior of a single, intrinsically flexible, weakly charged polyelectrolytechain in poor solvent is analyzed by extensive computer simulations combining Monte Carlo and moleculardynamics techniques. After determining the ϑ point for the charge-free case, we focus on the weakscreening limit, corresponding to low salt concentration in the solution. We study the dependence onboth the solvent strength, characterized by the relative deviation from the ϑ point, τ, and the fraction ofcharged monomers in the chain, which is effectively tuned by varying the Coulomb interaction parameter.The conformations are discussed in terms of global properties (such as the end-to-end distance, the inertiatensor components, etc.) and functions revealing more detailed information, such as the density distributionaround the center of mass and the structure factor. For chains in the ϑ regime our data confirm thepicture of a string of electrostatic blobs. For poorer solvents (up to τ = 0.4) we observe, upon increasingthe intrachain Coulomb repulsion, a splitting of the spherical globule into a dumbbell-type structure,accompanied by a sharp increase in the chain's gyration radius. For sufficiently large τ, a further splittingis observed as well. Such a “necklace globule” (a sequence of transitions) had been predicted by Dobrynin,Rubinstein and Obukhov (Macromolecules1996, 29, 2974), with a nontrivial scaling of the gyration radiuswith chain length and interaction parameters, which is confirmed by our data. By means of a scalinganalysis, we argue that the transitions can be interpreted as thermodynamic first-order phasetransformations, when taking the appropriate thermodynamic limit, which implies a scaling of theelectrostatic coupling with inverse chain length.
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