How does the chain extension of poly (acrylic acid) scale in aqueous solution?: A combined study with light scattering and computer simulation

This work addresses the question of the scaling behavior of polyelectrolytes in solution for a realistic prototype. We show results of a combined experimental (light scattering) and theoretical (computer simulations) investigation of structural properties of the sodium salt of poly (acrylic acid) (Na-PAA). Experimentally, we determined the molecular weight (M-W) and the hydrodynamic radius (R-H) by static and dynamic light scattering for six different Na-PAA samples in aqueous NaCl-containing solution (0.1-1 mol/l) of polydispersity D-P between 1.5 and 1.8. On the computational side, three different variants of a newly developed mesoscopic force field for Na-PAA were employed to determine R-H for monodisperse systems of the same M-W as in the experiments. The force field effectively incorporates atomistic information and one coarse-grained bead corresponds to one PAA monomer. We find that R-H matches with the experimental data for all investigated samples. The effective scaling exponent for R-H is found to be around 0.55, which is well below its asymptotic value for good solvents. Additionally, data for the radius of gyration (R-G) are presented. (C) 2002 American Institute of Physics.