The impact of structural details of polyelectrolyte molecules on the behavior of solutions and melts has been subject of growing interest motivated by a key role of such systems in many fields of science and by the need to tailor polyelectrolyte materials for various specific applications. In this work, we applied the model based on the recently developed statistical-field theory in the Random Phase Approximation (RPA) to examine the impact of structural details of a macromolecule on the structure and osmotic pressure of a salt-free aqueous solution. We consider different distributions of charged and neutral monomeric units along the backbone of polyelectrolyte chain, different hard-sphere diameters of these units and counterions, as well as the effects of chain elasticity and asymmetric distribution of electrical charge inside the ions. Taking realistic molecular characteristics of a macromolecule, we examine how the calculated partial structure factors and the osmotic pressure of a salt-free
solution respond to variations of the polyelectrolyte structural details over a wide concentration range, from dilute to concentrated solutions. Calculated results are compared with computer simulation and experimental data.