R. G. Winkler¹, T. Hofmann², and P. Reineker^2
1Institute Theory II
²Abteilung Theoretische Physik, Univeristät Ulm, 89069 Ulm

The structure of rodlike polyelectrolyte molecules in solution has been studied using the OrnsteinZernike integral equation for molecular systems. The polymer reference interaction site model together with the reference Laria-Wu-Chandler closure is solved numerically taking counterions into account explicitly. The counterions and the polymer chains interact through an unscreened Coulomb potential. The pair correlation functions among the different entities are calculated for various Bjerrum lengths and densities. Based upon these quantities, the effective potential between the monomers and the counterions, respectively, is extracted. Our calculations yield a minimum at short separations of the effective counterion-counterion and monomer-monomer potentials, respectively, corresponding to an attractive interaction between the equally charged units.