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Strong coupling electrostatic theory of polymer counterions close to planar charges

Strong coupling phenomena, such as the like charged macroions attraction, opposite charged macroions repulsion, charge renormalization or charge inversion, are known to be mediated by multivalent counterions. Most theories treat the counterions as point charges, and describe the system by a single coupling parameter that measures the strength of the Coulomb interactions. In many biological systems, the counterions are highly charged and have finite sizes and can be well-described by polyelectrolytes. The shapes and orientations of these polymer counterions play a major role in the thermodynamics of these systems. In this work we apply a field theoretic description in the strong coupling regime to polyelectrolytes. We work out the special cases of rod-like polymer counterions confined by one and two charged walls respectively. The effects of the geometry of the rod-like counterions and the excluded volume of the walls on the density, pressure and the free energy of the rodlike counterions are discussed.