Flexible Conjugated Polyelectrolyte Solutions:  A Small Angle Scattering Study

The aqueous solutions of a fully neutralized flexible conjugated polyacid, the poly(3-thiophene sodium acetate) (P3TNaA), are studied by small angle scattering techniques, as a function of polymer concentration, molecular weight and added salt concentration. The characteristic polyelectrolyte scattering peak obeys the predictions of the isotropic model, in good agreement with the behavior of saturated polyelectrolyte solutions. Despite the presence of irreversible aggregates formed during the synthesis, no further aggregation occurs in solution whatever the polymer or added salt concentration. Thus, these conjugated polyelectrolytes remain hydrosoluble and well-dispersed when the electrostatic repulsion is screened, probably due to their small bare persistence length that prevents large dispersion forces in the undoped state.