Dispersion mechanism of polyacrylic acid-coated nanoparticle in protic ionic liquid, N,N-diethylethanolammonium trifluoromethanesulfonate

Ryo Kanzaki; Clément Guibert; Jérôme Fresnais; Véronique Peyre

doi:10.1016/j.jcis.2018.01.004

Dispersion mechanism of polyacrylic acid-coated nanoparticle in protic ionic liquid, N,N-diethylethanolammonium trifluoromethanesulfonate

J Colloid Interface Sci. 2018 Apr 15:516:248-253. doi: 10.1016/j.jcis.2018.01.004. Epub 2018 Jan 3.

Authors

Ryo Kanzaki¹, Clément Guibert², Jérôme Fresnais², Véronique Peyre²

Affiliations

¹ Graduate School of Science and Engineering, Kagoshima University, 1-21-35, Korimoto, Kagoshima 890-0065, Japan. Electronic address: kanzaki@sci.kagoshima-u.ac.jp.
² Sorbonne Université, CNRS, Laboratoire Physico-Chimie des Electrolytes et des Nanosystèmes Interfaciaux, PHENIX, F-75005 Paris, France.

PMID: 29408111
DOI: 10.1016/j.jcis.2018.01.004

Abstract

Hypothesis: Ionic liquids (ILs) are extremely concentrated electrolyte solutions. The ubiquitous presence of ions induces specific behaviors for chemical reactions compared to reactions in water solutions. This is also the case for the stability of colloidal dispersions, for which the DLVO model cannot be applied as the ionic strength is out of the model range. In a previous work, in the protic IL ethylammonium nitrate (doi: https://doi.org//10.1016/j.jcis.2015.04.059), we observed an unexpected influence of the pH on the stability of dispersion of maghemite nanoparticles coated with poly(acrylic acid) (pAA).

Experiments: To clarify and generalize these observations, we investigated here the pH response of the dispersion in a second protic ionic liquid with a different acid-base nature, diethylethanolammonium trifluoromethanesulfonate. pH titrations of the dispersions were achieved with an IS-FET electrode and the associated thermodynamic constants determined. The colloid structural properties were examined by small angle X-ray scattering.

Findings: Under acidic or mildly basic condition, a stable dispersion was obtained, i.e., when the degree of dissociation of pAA, α, was α < 0.1 or α > 0.7. Dispersions form quite dense but reversible aggregates in the intermediate α range. A model for the solvation layer around the particles is proposed and generalizes the former findings.

Keywords: Colloidal stability; IFSET; Ionic liquid; Maghemite; Nanoparticles; Polyacrylic acid; Potentiometric titration; Small angle X-ray scattering.