Dilute solution behaviour of sodium polyacrylate chains in aqueous NaCl solutions

Combined static and dynamic light scattering was used to characterise a variety of sodium poly(acrylate) samples in dilute aqueous solutions with added NaCl. An increase of the NaCl content resulted in a decrease of the solvent quality. On the basis of these findings, two solvent conditions were selected for a detailed investigation of the coil size as a function of the molar mass M-w : aqueous 0.1 M NaCl represents a thermodynamically good solvent and aqueous 1.5 M NaCl is close to a Theta-solvent. If the NaCl content was kept within this range of 0.1 M less than or equal to [NaCl] less than or equal to 1.5 M, a single Kuhn segment length of l(k) = 4.2 nm and an excluded volume parameter of omega(0) = -0.04 for the corresponding neutral monomer [Muthukumar et al. Macromolecules 30; 1997: 8375] were able to adequately describe coil expansion as a function of the molar mass and the content of added salt. Towards lower salt contents, Muthukumar's approach which is based on the excluded volume parameter omega(0), the Kuhn segment length l(k) and an effective charge density f became increasingly inadequate. (C) 2003 Published by Elsevier Ltd.