Simulations of a lattice model of two-headed linear amphiphiles: influence of amphiphile asymmetry

TL;DR

This study uses 2D lattice Monte Carlo simulations to analyze how the architecture and asymmetry of two-headed linear amphiphiles affect their critical micelle concentration, revealing that spacer length has a stronger impact than asymmetry.

Contribution

It systematically investigates the influence of amphiphile asymmetry on CMC using a simplified lattice model, extending understanding of surfactant aggregation behavior.

Findings

CMC increases with spacer units for s<N/2

Asymmetry has a weaker effect on CMC than spacer length

Results align with experimental observations

Abstract

Using a 2D lattice model, we conduct Monte Carlo simulations of micellar aggregation of linear-chain amphiphiles having two solvophilic head groups. In the context of this simple model, we quantify how the amphiphile architecture influences the critical micelle concentration (CMC), with a particular focus on the role of the asymmetry of the amphiphile structure. Accordingly, we study all possible arrangements of the head groups along amphiphile chains of fixed length $N=12$ and 16 molecular units. This set of idealized amphiphile architectures approximates many cases of symmetric and asymmetric gemini surfactants, double-headed surfactants and boloform surfactants. Consistent with earlier results, we find that the number of spacer units $s$ separating the heads has a significant influence on the CMC, with the CMC increasing with $s$ for $s<N/2$. In comparison, the influence of the asymmetry of the chain architecture on the CMC is much weaker, as is also found experimentally.