Work

Superchaotropic or Hydrophobic Behavior? How Borate Clusters Assemble with Nonionic Surfactants

Year: 2026

Type: article

Abstract: This work investigates the interaction of anionic borate clusters with self-assembled surfactant systems. Anionic borate clusters, such as closo-dodecaborates B12X122- (X = H, Cl, Br, I) and cobaltabisdicarbollide (COSAN-), bind hydrated solutes via a water-mediated (super)chaotropic effect. Cloud point measurements on the micellar phase of the nonionic surfactant C8E4 reveal a continuous series of binding affinity from chaotropic (B12H122-) over superchaotropic (B12Cl122-, B12Br122-) to hydrophobic ions (B12I122-, COSAN), extending seamlessly the Hofmeister series of classical ions and in line with data for ten additional nanometer-sized ions gleaned from the literature. Small-angle X-ray and neutron scattering revealed a structural criterion distinguishing superchaotropic from hydrophobic ions. Superchaotropic ions form a saturated interfacial monolayer between surfactant headgroups. Hydrophobic ions, however, localize in the apolar interior of the micelle, causing a curvature transition into bilayer structures in C8E4, a surfactant system that does not form bilayers on its own, leading to micellar destabilization and phase separation at higher concentrations.

Source: The Journal of Physical Chemistry Letters

DOI: 10.1021/acs.jpclett.6c01815

Authors: Max Hohenschutz, Sanyukta Bhattacharjee, Olivier Diat, Pierre Bauduin

Institutions: Centre National de la Recherche Scientifique, Université de Montpellier, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, CEA Marcoule, Institut de Chimie Séparative de Marcoule

Language: English

Topic: Surfactants and Colloidal Systems

Subfield: Organic Chemistry

Field: Chemistry

Domain: Physical Sciences

Open Access status: green

Funder: Agence Nationale de la Recherche

Award: Leaching foams to extract metals from electronic wastes