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Computational predictions of interfacial tension, surface tension, and surfactant adsorption isotherms

Li, Jing; Amador, Carlos; Wilson, Mark R.

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Authors

Jing Li jing.li@durham.ac.uk
PGR Student Doctor of Philosophy

Carlos Amador



Abstract

All-atom (AA) molecular dynamics (MD) simulations are employed to predict interfacial tensions (IFT) and surface tensions (ST) of both ionic and non-ionic surfactants. The general AMBER force field (GAFF) and variants are examined in terms of their performance in predicting accurate IFT/ST, γ, values for chosen water models, together with the hydration free energy, ΔGhyd, and density, ρ, predictions for organic bulk phases. A strong correlation is observed between the quality of ρ and γ predictions. Based on the results, the GAFF-LIPID force field, which provides improved ρ predictions is selected for simulating surfactant tail groups. Good γ predictions are obtained with GAFF/GAFF-LIPID parameters and the TIP3P water model for IFT simulations at a water–triolein interface, and for GAFF/GAFF-LIPID parameters together with the OPC4 water model for ST simulations at a water–vacuum interface. Using a combined molecular dynamics-molecular thermodynamics theory (MD-MTT) framework, a mole fraction of C12E6 molecule of 1.477 × 10−6 (from the experimental critical micelle concentration, CMC) gives a simulated surface excess concentration, ΓMAX, of 76 C12E6 molecules at a 36 nm2 water–vacuum surface (3.5 × 10−10 mol cm−2), which corresponds to a simulated ST of 35 mN m−1. The results compare favourably with an experimental ΓMAX of C12E6 of 3.7 × 10−10 mol cm−2 (80 surfactants for a 36 nm2 surface) and experimental ST of C12E6 of 32 mN m−1 at the CMC.

Journal Article Type Article
Acceptance Date Mar 27, 2024
Online Publication Date Mar 27, 2024
Publication Date Apr 21, 2024
Deposit Date Mar 28, 2024
Publicly Available Date Apr 18, 2024
Journal Physical Chemistry Chemical Physics
Print ISSN 1463-9076
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 26
Issue 15
Pages 12107-12120
DOI https://doi.org/10.1039/d3cp06170a
Public URL https://durham-repository.worktribe.com/output/2349719

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