Physicochemical characterization of green sodium oleate-based formulations. Part 1. Structure and rheology

Duccio Tatini; Martina Raudino; Moira Ambrosi; Emiliano Carretti; Irina Davidovich; Yeshayahu Talmon; Barry W Ninham; Pierandrea Lo Nostro

doi:10.1016/j.jcis.2021.01.040

Physicochemical characterization of green sodium oleate-based formulations. Part 1. Structure and rheology

J Colloid Interface Sci. 2021 May 15:590:238-248. doi: 10.1016/j.jcis.2021.01.040. Epub 2021 Jan 21.

Authors

Duccio Tatini¹, Martina Raudino¹, Moira Ambrosi¹, Emiliano Carretti¹, Irina Davidovich², Yeshayahu Talmon², Barry W Ninham³, Pierandrea Lo Nostro⁴

Affiliations

¹ Department of Chemistry "Ugo Schiff" and CSGI, University of Florence, 50019 Sesto Fiorentino (Firenze), Italy.
² Department of Chemical Engineering and the Russell Berrie Nanotechnology Institute (RBNI), Technion - Israel Institute of Technology, Haifa 3200003, Israel.
³ Department of Applied Mathematics, Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200, Australia.
⁴ Department of Chemistry "Ugo Schiff" and CSGI, University of Florence, 50019 Sesto Fiorentino (Firenze), Italy. Electronic address: pierandrea.lonostro@unifi.it.

PMID: 33548607
DOI: 10.1016/j.jcis.2021.01.040

Abstract

Hypothesis: The structure, rheology and other physicochemical properties of dilute aqueous dispersions of sodium oleate (NaOL) are well known. This paper is the first report in which a moderately concentrated (13% w/w) dispersion of NaOL in water is investigated. In fact, at this concentration the phase and rheology behavior of the surfactant remarkably deviates from those of its dilute solutions in water and a significant effect is imparted by the addition of potassium chloride.

Experimental: The structural, thermal and rheological properties of a 13% w/w dispersion of NaOL in water were investigated by cryo-TEM, rheology, and DSC experiments with and without the addition of potassium chloride. The system is comprised of elongated wormlike micelles that turn into a gel-like more disordered viscous material upon addition of small amounts of KCl (4% w/w).

Findings: This paper illustrates the multifaceted behavior of sodium oleate dispersions at intermediate concentrations that depends on the presence of other cosolutes (such as KCl). The results show that viscoelastic aqueous dispersions of NaOL are excellent candidates for the preparation of stimuli-responsive green materials to be used in a number of different applications. We also discuss the genesis of wormlike micelles (WLMs) in terms of the general theory of self-assembly.

Keywords: Green formulation; Sodium oleate; Soft matter; Viscoelasticity; Wormlike micelles.