A small-angle neutron scattering study of poly(ethylene oxide) microstructure in aqueous poly(styrenesulfonate sodium) solutions

Dilute aqueous solutions of d-PEO and PSSNa mixtures were studied by 2H NMR spectroscopy and small-angle neutron scattering (SANS). The interactions between d-PEO and PSSNa were found to be negligible both in the presence and absence of NaCl. At very dilute concentration (0.7 mg mL−1), d-PEO chains were still found to be slightly collapsed at ambient temperature in water. Upon the addition of PSSNa, aggregates of d-PEO were observed with d-PEO coils loosely associated with each other. The average centre to centre distance between d-PEO coils, which was calculated from the maxima in SANS spectra, was similar to the size of the individual coils. The effect of a simple salt, NaCl, on d-PEO-PSSNa interaction was investigated. Salt addition induced a breakdown of the dilute d-PEO aggregates.

Depletion interactions owing to non-interacting PSSNa assist the formation of dilute PEO aggregates, which break down upon adding simple screening salt.Figure optionsDownload high-quality image (65 K)Download as PowerPoint slideHighlights
► PEO molecules form Gaussian chains in dilute aqueous solutions at ambient temperature.
► With added PSSNa depletion interactions assist the formation of dilute PEO aggregates.
► These dilute PEO aggregates break down upon adding simple screening salt.