Swollen Micelles Plus Hydrophobically Modified Hydrosoluble Polymers in Aqueous Solutions: Decoration Versus Bridging. a Small Angle Neutron Scattering Study

TL;DR

This study uses small angle neutron scattering to analyze how hydrophobically modified PEO polymers affect interactions between oil droplets in water, revealing decoration versus bridging effects and their impact on phase separation.

Contribution

It provides a comparative analysis of decoration and bridging mechanisms of hydrophobically modified PEO on microemulsion droplets using neutron scattering.

Findings

PEO-m induces repulsive interactions between droplets.

PEO-2m induces attractive interactions leading to phase separation.

Droplet size remains stable with up to 40 hydrophobic chains attached.

Abstract

In this paper we examine the effective interactions introduced between the droplets of an oil in water microemulsion upon progressive addition of hydrophobically modified water soluble poly(ethylene oxide)-PEO using essentially small angle neutron scattering. To discuss the relative importance of decoration and bridging of the droplets we compare analogous samples with addition of a PEO grafted at both extremities with hydrophobic C12H 25 chains (PEO-2m) or addition of a PEO grafted at one extremity only with a C12H 25 chain (PEO-m). PEO-m or PEO-2m adsorb onto the droplets via their hydrophobic extremities and the droplets are found to retain their form and size upon addition of up to 40 hydrophobic C12H 25 chains per droplet. When the volume fraction of droplets is less than about 10%, the effective interactions introduced by PEO-m or PEO-2m are found to be very different: PEO-m introduces a repulsive interaction while PEO-2m introduces an effective attractive interaction. This attractive interaction leads to an associative phase separation in the range of low volume fraction when a sufficient amount of PEO-2m is added.