Oppositely Charged Polyelectrolytes in Solution

Abstract: This thesis is about the formation of complexes in solutions of oppositely charged polyions. We consider mainly three topics: 1)Monte Carlo simulations of oppositely charged polyelectrolytes with a focus on cluster compositions. To explain the distribution of cluster compositions, we found a minimum set of rules describing the interplay between the energy and entropy. 2)An analytical theory. The simulation results obtained in a canonical ensemble suffer from finite-size effects, since there are only a few polyions in the simulation box. We could reproduce the simulation results in the canonical ensemble and extended the calculations to a grand canonical ensemble. The latter ensemble corresponds more closely to experimental systems. 3)An analytical theory for a single polyelectrolyte with multivalent counterions. DNA can be compacted by multivalent counterions. As the concentration of the condensing agent increases, DNA compaction shows either an all-or-none transition or something in between, a transitions with pearl-necklace structures (partial globules connected by subchains). We focus on whether a coil-globule transition is discontinuous or continuous.