Interfacial silica nanoparticles stabilize cocontinuous polymer blends

TL;DR

This study demonstrates how silica nanoparticles at interfaces can stabilize cocontinuous polymer structures, providing insights into their formation, stability, and rheological behavior through advanced microscopy and rheology techniques.

Contribution

First real-time visualization of coalescence in nanoparticle-stabilized polymer blends and analysis of their rheological properties and stability mechanisms.

Findings

Nanoparticles suppress coalescence by covering interfaces.

Rheological response linked to interface shrinkage and particle network.

Particle scaffold persists after phase remixing.

Abstract

We investigated the formation of cocontinuous structures in polymer blends. These polymeric bijels (bicontinuous interfacially jammed emulsion gels) were composed of polystyrene oligomer, polybutene and fluorescent hydrophobic silica nanoparticles. A micron-sized cocontinuous morphology was stabilized by a monolayer of silica nanoparticles at the interface. Real-time observation of coalescence dynamics in co-continuous polymer blends stabilized by interfacial particles was for the first time achieved via laser scanning confocal microscopy. We demonstrated that suppression of coalescence arises from coverage of interfaces by nanoparticles. Furthermore, by combining confocal microscopy with rheology, we correlated the rheological response of a cocontinuous structure with its morphology change. We found that the rheological behavior can be attributed to competition between interface shrinkage and particle network formation. In addition, we showed that a particle scaffold is maintained even after the remixing of two polymer phases above the spinodal point. Finally, we also discussed differences between the shear response of the particle-stabilized cocontinuous structure and normal colloidal gels: the former one is more fragile than the latter under shear.