Micellar Aggregates of Gemini Surfactants: Monte Carlo Simulation of a Microscopic Model

TL;DR

This study uses Monte Carlo simulations of a microscopic model to analyze how structural variations in gemini surfactants influence their critical micellar concentration and aggregate shapes, aligning well with experimental data.

Contribution

It introduces a detailed microscopic model and extensive simulations to understand the effects of molecular geometry on gemini surfactant behavior, providing insights consistent with experiments.

Findings

CMC varies with spacer length, tail length, and chain rigidity.

Micellar shapes depend on molecular geometry and charge.

Simulation results match experimental trends.

Abstract

We propose a "microscopic" model of gemini surfactants in aqueous solution. Carrying out extensive Monte Carlo simulations, we study the variation of the critical micellar concentration (CMC) of these model gemini surfactants with the variation of the (a) length of the spacer connecting the two hydrophilic heads, (b) length of the hydrophobic tail and (c) the bending rigidity of the hydrocarbon chains forming the spacer and the tail; some of the trends of variation are counter-intuitive but are in excellent agreement with the available experimental results. Our simulations also elucidate the dependence of the shapes of the micellar aggregates and the magnitude of the CMC on the geometrical shape and size of the surfactant molecules and the electrical charge on the hydrophilic heads.