2019/12/16 by Carlos G. Lopez, Lopez, Carlos G., Ferenc Horkay +7
Chemistry · Materials Science · Physics and Astronomy · #Chemical Physics (physics.chem-ph) #Electrostatics and Colloid Interactions #FOS: Physical sciences #Material Dynamics and Properties #NMR spectroscopy and applications #Soft Condensed Matter (cond-mat.soft)
paper · pdf · doi:10.48550/arxiv.1912.07487
openalex publication_date 2019/12/16 · openalex created_date 2022/07/26 · openalex updated_date 2026/07/28
We report results of small angle neutron scattering measurements made on\nsodium polystyrene sulfonate in aqueous salt solutions. The correlation length\nand osmotic compressibility are measured as a function of polymer (c) and added\nsalt (cS) concentrations, and the results are compared with scaling\npredictions and the random-phase approximation (RPA). In Dobrynin et al's\nscaling model the osmotic pressure consists of a counter-ion contribution and a\npolymer contribution. The polymer contribution is found to be two orders of\nmagnitude smaller than expected from the scaling model, in agreement with\nearlier observations made on neutral polymers in good solvent condition. RPA\nallows the determination of single-chain dimensions in semidilute solutions at\nhigh polymer and added salt concentrations, but fails for cS < 2 M. The \χ\nparameter can be modelled as the sum of an intrinsic contribution and an\nelectrostatic term: \χ \≃ \χ0+K/cS1/2, where \χ0 > 0.5 is\nconsistent with the hydrophobic nature of the backbone of NaPSS. The dependence\nof \χelec \≃ 1/cS1/2 disagrees with the random-phase\napproximation (\χelec \≃ 1/cS), but agrees with the light\nscattering results in dilute solution and Dobrynin et al's scaling treatment of\nelectrostatic excluded volume.\n