Dilute solution behaviour of sodium polyacrylate chains in aqueous NaCl solutions

Abstract

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 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 l k =4.2 nm and an excluded volume parameter of ω 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 ω 0, the Kuhn segment length l k and an effective charge density f became increasingly inadequate.