Structure factor of polymers interacting via a short range repulsive potential: application to hairy wormlike micelles

TL;DR

This paper uses the Random Phase Approximation to analyze the structure factor of polymers with short-range repulsive interactions, applying the model to interpret small angle neutron scattering data of hairy wormlike micelles, revealing concentration-dependent peaks.

Contribution

It introduces a quantitative RPA-based model for the structure factor of polymers with short-range repulsion, applied to experimental micelle solutions.

Findings

S(q) exhibits a concentration-dependent peak above a threshold density.

The model accurately fits small angle neutron scattering profiles.

The potential range controls the threshold concentration for peak emergence.

Abstract

We use the Random Phase Approximation (RPA) to compute the structure factor, S(q), of a solution of chains interacting through a soft and short range repulsive potential V. Above a threshold polymer concentration, whose magnitude is essentially controlled by the range of the potential, S(q) exhibits a peak whose position depends on the concentration. We take advantage of the close analogy between polymers and wormlike micelles and apply our model, using a Gaussian function for V, to quantitatively analyze experimental small angle neutron scattering profiles of semi-dilute solutions of hairy wormlike micelles. These samples, which consist in surfactant self-assembled flexible cylinders decorated by amphiphilic copolymer, provide indeed an appropriate experimental model system to study the structure of sterically interacting polymer solutions.