SAXS from Four‐Arm Polyelectrolyte Stars in Semi‐Dilute Solutions

Abstract

We have performed small‐angle X‐ray scattering experiments on semi‐dilute solutions of highly charged star polyelectrolytes. Poly(sodium acrylate) (PANa) and poly(cesium acrylate) (PACs) stars with four arms were successfully synthesized by a combination of atom transfer radical polymerization and chemical modifications. Over a wide range of polyelectrolyte concentration Cp, these two systems as well as their equivalent linear polyelectrolytes were investigated at different ionic strengths. Scattering experiments show the existence of a scattering peak denoted as qmax, which disappears with the addition of a simple electrolyte, evidencing the electrostatic character of the interactions. We have also studied the effect of the charge parameter and the nature of the counterion (Na and Cs) on the scattering properties of these star polyelectrolytes. In the case of PACs, qmax scales with the polyelectrolyte concentration as Cp1/2 over the whole range of studied concentrations, whereas it scales as Cp1/2 (for Cp < 45 mg · ml−1) and Cp1/4 (for Cp > 45 mg · ml−1) in the case of PANa. Variation of qmax as a function of polyelectrolyte concentration Cp for PA1Cs (○) and PA2Cs (•) stars (error bars are indicated).magnified imageVariation of qmax as a function of polyelectrolyte concentration Cp for PA1Cs (○) and PA2Cs (•) stars (error bars are indicated).

Small‐Angle X‐Ray Scattering on Solutions of Carboxymethylcellulose and Bovine Serum Albumin

“…Scattering techniques have proved to be powerful tools to study the properties of polyelectrolytes in solution 22–28. Figure 1 shows the variation of I ( q ) as a function of q for pure CMC solutions at the concentrations C p of 5 × 10 −3 g · mL −1 and 10 × 10 −3 g · mL −1 .…”

Synthesis, Characterization and Behavior in Aqueous Solution of Star‐Shaped Poly(acrylic acid)

“…This approach was applied to the synthesis of PAA stars using ATRP of tBA. Schnitter et al39 used an initiator with six α ‐bromoester functions, esterified with a dendritic core, whereas Moinard et al40 used a core carrying four benzyl bromide functions.…”

Scattering Study of the Structure of Polystyrene Sulfonate Comb Polyelectrolytes in Solution

“…[21] To our knowledge comb PSS has not been examined in detail previously, although a four arm PSS star has been subject to a small-angle X-ray scattering (SAXS) study. [22] The analysis of structural information in polyelectrolytes is particularly challenging, since the long range nature of the charge interaction complicates the analysis of scattering experiments. [23] Simulations of uncharged comb polymers indicate worm-like conformations in good solvents due to the induced rigidity effect of the side-chain entropy on the backbone.…”