# Self-Assembled Sodium Dodecyl Sulfate Structures on Mineral Surfaces Following Rapid Solvent Removal

## TL;DR

This study explores how sodium dodecyl sulfate (SDS) self-assembles on mineral surfaces after rapid solvent removal, revealing diverse structures influenced by the substrate and environmental conditions.

## Contribution

The paper provides new insights into SDS self-assembly at the solid–air interface, highlighting the role of substrate and environmental factors.

## Key findings

- SDS forms hemicylindrical micelles, lamellar bilayers, and quasi-1D structures on HOPG, talc, and mica.
- Lamellar bilayers on talc are thermally stable up to 160 °C, while quasi-1D structures on mica lose organization at 60 °C.
- Mica supports methyl-terminated monolayers and thinner lamellar structures, indicating substrate-specific interactions.

## Abstract

Sodium dodecyl sulfate
(SDS) is a widely used surfactant with applications
ranging from detergents to cell lysis and nanomaterial exfoliation.
Additionally, SDS can form self-assembled structures on different
substrates under specific conditions. While extensive research has
explored SDS self-assembly at the liquid–solid interface, less
is known about the structures formed at the solid–air interface
following solvent removal. In this study, we investigated SDS self-assembled
structures on HOPG (highly oriented pyrolytic graphite), talc, and
mica substrates using spin-coating and spread-coating methods. Scanning
probe microscopy revealed a range of morphologies, including hemicylindrical
micelles, lamellar bilayers, and quasi-1D structures, shaped by the
interaction between SDS and the substrate surface. On HOPG, hemicylindrical
micelles were observed in dilute solutions, whereas lamellar 2D structures,
likely bilayer stacks, formed in both dilute and concentrated samples.
On talc, lamellar bilayers demonstrated temporal evolution and thermal
stability up to 160 °C. Mica samples exhibited quasi-1D structures,
2D bilayers, and thinner lamellar 2D structures, with evidence suggesting
the presence of a methyl-terminated monolayer. Thermal annealing tests
indicated that quasi-1D structures lost organization at 60 °C,
whereas bilayers remained stable up to 150 °C, at least. The
results highlight the complexity of SDS self-assembly at the solid–air
interface, emphasizing the critical role of local environmental factors.
These findings provide insights into surfactant behavior during solvent
removal and establish a foundation for further exploration of self-assembled
systems under ambient conditions.