Scattering and viscosimetric behaviors of four- and six-arm star polyelectrolyte solutions

This paper discusses the scattering and viscosity results of four- and six-arm sodium, cesium, and rubidium polyacrylate (PANa, PACs, PARb) star polyelectrolyte solutions in comparison with their equivalent linear polyelectrolyte chains. The polyelectrolyte effect is highlighted in these systems, and an estimate of the persistence length is deduced from static light scattering and X-ray scattering. Static and dynamic light scattering studies permitted to determine their mass average molar mass 〈M_w〉, their radius of gyration 〈R_g〉, their second virial coefficient A₂, their hydrodynamic radius A_H, and their persistence length L_P. The polyelectrolyte "abnormal" behavior was observed in the variation of the reduced viscosity η _red as a function of the polyelectrolyte concentration C_P on linear and star systems (existence of a maximum in η_red vs C_P). Additionally to the specific behavior brought by the star architecture, the results also show an important effect due to the type of counterions and the charge parameter on the scattering and the viscometric properties. A systematic comparison between linear and star polyelectrolytes having similar molar mass, counterions, and charge parameter is presented.