Screening lengths and osmotic compressibility of flexible polyelectrolytes in excess salt solutions

Abstract

<p>We report results of small angle neutron scattering measurements made on sodium polystyrene sulfonate in aqueous salt solutions. The correlation length (ξ) and osmotic compressibility are measured as a function...</p>

Charge Modification as a Mechanism for Tunable Properties in Polymer–Surfactant Complexes

“…For most of the samples, the PE contrast shows that thin rods remain as the preferred solution structure for the cat-HEC polymers, though with a radius smaller than those of the parent cat-HEC PEs. This shows that the [ ] sufficiently neutralise the positively charged groups within the PE backbone, leading to less repulsions between the PE units and formation of a more compact structure [ 41 , 42 , 43 ]. Further evidence for this can be seen in Figure 7 , whereby the 0.5, 0.95, and 1.8% degree of modification cat-HEC-containing complexes (PE contrast) display an apparent loss of repulsive S(Q) peaks when compared with the PE only samples, emphasising the loss of repulsions between the PE units.…”

Diffusion and Viscosity of Unentangled Polyelectrolytes

“…Dobrynin and Jacobs estimated a lower value of c D ≃ 0.26 M for NaPSS in salt-free water from viscosity data. Neutron scattering data show, however, that chains appear to be swollen with respect to their uncharged dimensions up to at least c ≃ 4 M. , …”

“…We next review the experimental and simulation results from the literature, focusing on NaPSS in water, the most extensively studied polyelectrolyte system. ,− ,,,,,,, Of particular interest for this study is the fact that the specific viscosity of NaPSS shows a strong increase with polymer concentration beyond c ≃ 1 M, displaying exponential behavior that is not anticipated by scaling …”

“…The strong, long-range electrostatic interactions between like-charged chains indicate that polyelectrolyte solutions and gels are highly correlated systems, − for which the success of mean-field theories (e.g., the random phase approximation) is limited, particularly in low ionic strength media. ,, Scaling models, following the pioneering work of de Gennes and co-workers, − provide a relatively simple and useful framework to understand polyelectrolyte behavior and are particularly successful in predicting the conformational properties of flexible polyelectrolytes in solution. ,, The scaling treatment of polyelectrolyte dynamics, on the other hand, displays poorer agreement with experimental results. ,− …”

“…7,16,17 Scaling models, following the pioneering work of de Gennes and coworkers, 18−23 provide a relatively simple and useful framework to understand polyelectrolyte behavior and are particularly successful in predicting the conformational properties of flexible polyelectrolytes in solution. 17,24,25 The scaling treatment of polyelectrolyte dynamics, on the other hand, displays poorer agreement with experimental results. 24,26−30 In salt-free or low ionic strength media, polyelectrolytes adopt highly extended conformations, 24,29−40 which indicates that their solutions are above the overlap concentration (c*) for most practical applications.…”