Precipitation-Redispersion of Cerium Oxide Nanoparticles with Poly(Acrylic Acid) : Towards Stable Dispersions

TL;DR

This study demonstrates a precipitation-redispersion mechanism using poly(acrylic acid) to stabilize cerium oxide nanoparticle dispersions across a wider pH and ionic strength range, enhancing their practical utility.

Contribution

It introduces a novel method of stabilizing cerium oxide nanoparticles through polymer complexation, extending their stability range in various conditions.

Findings

Redispersion occurs at higher pH, forming stable single-particle solutions.

Approximately 40-50 polymer chains adsorb per nanoparticle in stable dispersions.

Polymer complexation significantly improves dispersion stability across pH and ionic strength variations.

Abstract

We exploit a precipitation-redispersion mechanism for complexation of short chain polyelectrolytes with cerium oxide nanoparticles to extend their stability ranges. As synthesized, cerium oxide sols at pH 1.4 consist of monodisperse cationic nanocrystalline particles having a hydrodynamic diameter of 10 nm and a molecular weight 400000 gmol-1. We show that short chain uncharged poly(acrylic acid) at low pH when added to a cerium oxide sols leads to macroscopic precipitation. As the pH is increased, the solution spontaneously redisperses into a clear solution of single particles with an anionic poly(acrylic acid) corona. The structure and dynamics of cerium oxide nanosols and their hybrid polymer-inorganic complexes in solution are investigated by static and dynamic light scattering, X-ray scattering, and by chemical analysis. Quantitative analysis of the redispersed sol gives rise to an estimate of 40 - 50 polymer chains per particle for stable suspension. This amount represents 20 % of the mass of the polymer-nanoparticle complexes. This complexation adds utility to the otherwise unstable cerium oxide dispersions by extending the range of stability of the sols in terms of pH, ionic strength and concentration.