Molecular Modelling of Basic Interactions in Fine Chemical Formulations
Mathias Lundgren (previous student, left the group in 2003)
This project is focusing on interfacial properties near the solid-liquid and liquid-vapor interfaces. We have performed molecular dynamics simulations at the atomistic level of small droplets on both hydrophobic and hydrophilic surfaces. The effect on addition of surface active molecules are also studied. In industry, this can be applied to sugar-based surfactants added to pesticides to approve wetting properties. Without the addition droplets of pesticide solution are likely to bounce of the hydrophobic surfaces of leafs, leading to a lack of absorption and a loss of the applied product. Our simulations are giving useful information about wetting processes at the molecular length scale.
Project Summary
To date, most theoretical work of wetting of surfaces has focused on pure liquids, and surprisingly there have been few studies of the effects of additives in liquid droplets on surfaces despite their evident industrial importance. For many industrial applications, the wetting requires to be rapid and uniform. To achieve such spreading, wetting is modified by lowering the surface tension through addition of surface-active species such as surfactants, polymers or alcohols. It is important to understand such processes at a molecular length scale.
Computer simulations have been shown to be a useful tool for the investigation of wetting phenomena. This method gives detailed information on both dynamic and structural behavior. We have performed molecular dynamics simulations at the atomistic level of droplets on both hydrophobic and hydrophilic surfaces, taking proper account of the long-range electrostatic forces. Even for droplets containing a few thousand molecules, the calculated contact angles are close to the experimental macroscopic value. An investigation of drops on a complex hydrophobic landscape where the water can enter surface pores and interact with hot spots on corners has been carried out. We have also measured the effect of short-chain surface-active molecules where interesting structural phenomena occur at the three-phase point as well at the liquid/vapor and liquid/solid interface.
Links
Snapshots and movies from simulations
Publications
Wetting of Water and Water/Ethanol Droplets on a Non-Polar Surface: A Molecular Dynamics Study, Lundgren, M.; Allan, N.L.; Cosgrove, T.; George N. Langmuir, 2002, 18, 10462
A Molecular Dynamics Study of Wetting of a Pillar-Surface, Langmuir, 2003, 19, 7127
Awards
2001 Molecular Science Research Day: 1st Price for Best Poster
2003 Molecular Science Research Day: 1st Price for Best Oral Presentation
This project is funded by the University of Bristol, EPSRC and Syngenta.
