Molecular dynamics of soft wetting

Soft polymeric solids, as also found in nature, have gained a great interest among scientists and engineers. Their structure and properties allow for unique behavior and potential applications, in for example lubrication, anti-fouling, stimuli-response and filtering.

A property that is unique to these soft solids, is their low elastic modulus, and consequentially, their response to surface tensions, both in interactions with other liquids, and with gases. For example, the surface tension forces between a droplet wetting a soft solid substrate, will pull on the substrate and cause it to deform into a resulting wetting ridge. The size of such a wetting ridge reaches macroscopic scales for soft solids, meaning that the wetting behavior diverges from classical wetting laws that focus on rigid solids.

Knowing that soft wetting behavior cannot be described using classical wetting laws, this thesis aims to shed further light and insights on the wetting behavior of such soft solids, by using Molecular Dynamics simulations. Gaining a true understanding of the fundamental behavior of these substances on a molecular level, allows us to explore all possibilities that these soft solids offer.

In this thesis, we explored the wetting phase transitions present for wetted polymer brushes, and the importance of taking into account both enthalpic and entropic effects in determining what wetting states are to be found for the wetting of polymer brushes. We also explored the difference between surface free energies and surface tensions for soft solids, where we report ways to quantify the difference between the two.