Structure of a 3-component polyelectrolyte solution model with dimerizing counterions and coions

The effect of dimerization between counterions and/or colons on the structu re of the three-component primitive model of polyelectrolyte solution is st udied using the integral equation technique for associating fluids. The thr ee-component system contains large and highly charged macroions, intermedia te size and charge colons and small monovalent counterions. In addition to the Coulomb forces, the counterions and colons also interact via short-rang e directional attractive forces which cause the formation of the dimers. It is demonstrated that dimerization effects are primarily of electrostatic o rigin and can be seen at lower concentrations. For the higher concentration regime, dimerization of the colons does not appreciably change correlation between the particles. In particular, the depletion interaction between th e macroions, which is of packing origin, is not effected by the dimerizatio n of the colons. The effect of the macroionic charge on the dimerization of the counterions is also studied. It is shown, that the increase of the mac roionic charge causes the dimerization process to be more intensive. (C) 20 01 Elsevier Science B.V. All rights reserved.