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 Mw: aqueous 0.1 M NaCl represents a thermodynamically good solvent and aqueous 1.5 M NaCl is close to a Θ-solvent. If the NaCl content was kept within this range of 0.1 M≤[NaCl]≤1.5 M, a single Kuhn segment length of lk=4.2 nm and an excluded volume parameter of ω0=−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, Muthukumarʹs approach which is based on the excluded volume parameter ω0, the Kuhn segment length lk and an effective charge density f became increasingly inadequate.