期刊
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
卷 581, 期 -, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.colsurfa.2019.123810
关键词
Molecular dynamics simulation; Surfactants; Water droplets; Spreading; Coarse-grained models; Statistical associating fluid theory; Superspreading
资金
- European Union [778104]
- Engineering and Physical Sciences Research Council (EPSRC) of the U.K. [EP/I018212, EP/J010502, EP/R013152]
- PLGrid Infrastructure
The surfactant-driven spreading of droplets is an essential process in many applications ranging from coating flow technology to enhanced oil recovery. Despite the significant advancement in describing spreading processes in surfactant-laden droplets, including the exciting phenomena of superspreading, many features of the underlying mechanisms require further understanding. Here, we have carried out molecular dynamics simulations of a coarse-grained model with a force-field obtained from the statistical associating fluid theory to study droplets laden with common and superspreading surfactants. We have confirmed the important elements of the superspreading mechanism, i.e. the adsorption of surfactant at the contact line and the fast replenishment of surfactant from the bulk. Through a detailed comparison of a range of droplets with different surfactants, our analysis has indicated that the ability of surfactant to adsorb at the interfaces is the key feature of the superspreading mechanism. To this end, surfactants that tend to form aggregates and have a strong hydrophobic attraction in the aggregated cores prevent the fast replenishment of the interfaces, resulting in reduced spreading ability. We also show that various surfactant properties, such as diffusion and architecture, play a secondary role in the spreading process. Moreover, we discuss various drop properties such as the height, contact angle, and surfactant surface concentration, highlighting differences between superspreading and common surfactants. We anticipate that our study will provide further insight for applications requiring the control of wetting.
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