Structured liquids with interfacial robust assemblies of a nonionic crystalline surfactant

Hypothesis: The structuring of liquids, that is, the kinetic trapping of nonequilibrium shapes of liquid-liquid interfaces, shows great promise for various applications, especially all-liquid devices. The strategies reported thus far to stabilize such unstable states include interfacial jamming of large colloidal particles and interfacial coassembly of elaborate molecules and/or nanoparticles. However, the structuring of liquids using a simple molecular surfactant has not been sufficiently demonstrated. We hypothesized that a surfactant with strong intermolecular interactions would form interfacial assemblies that behave substantially as solid particles for the structuring of liquids. Experiments: n-Octyl cello-oligosaccharide, a novel nonionic surfactant developed recently was explored as a candidate because of the ability of cello-oligosaccharides to form robust crystalline assemblies. Interfacial assembly of the nonionic crystalline surfactant was investigated for various water-organic solvent interfaces via pendant drop tensiometry and emulsification. Findings: The crystalline surfactant was found to self-assemble and form a crystalline monolayer at water-organic solvent interfaces, allowing arrested shape changes of the liquid-liquid interfaces. Irregular-shaped liquid droplets were successfully created under various solution conditions, such as various organic solvents for the oil phase and the water phase with high ionic strengths and harsh pH values. (c) 2021 Elsevier Inc. All rights reserved.

Automated summary

The study demonstrates that using nonionic crystalline surfactants can form a crystalline monolayer at water-organic solvent interfaces, allowing arrested shape changes of liquid-liquid interfaces. This enables the successful creation of irregular-shaped liquid droplets under various solution conditions.