Nonequilibrium configurations of swelling polymer brush layers induced by spreading drops of weakly volatile oil

Özlem Kap, Simon Hartmann, Harmen Hoek, Sissi De beer, Igor Siretanu, Uwe Thiele, Frieder Mugele*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

4 Citations (Scopus)
41 Downloads (Pure)


Polymer brush layers are responsive materials that swell in contact with good solvents and their vapors. We deposit drops of an almost completely wetting volatile oil onto an oleophilic polymer brush layer and follow the response of the system upon simultaneous exposure to both liquid and vapor. Interferometric imaging shows that a halo of partly swollen polymer brush layer forms ahead of the moving contact line. The swelling dynamics of this halo is controlled by a subtle balance of direct imbibition from the drop into the brush layer and vapor phase transport and can lead to very long-lived transient swelling profiles as well as nonequilibrium configurations involving thickness gradients in a stationary state. A gradient dynamics model based on a free energy functional with three coupled fields is developed and numerically solved. It describes experimental observations and reveals how local evaporation and condensation conspire to stabilize the inhomogeneous nonequilibrium stationary swelling profiles. A quantitative comparison of experiments and calculations provides access to the solvent diffusion coefficient within the brush layer. Overall, the results highlight the—presumably generally applicable—crucial role of vapor phase transport in dynamic wetting phenomena involving volatile liquids on swelling functional surfaces.
Original languageEnglish
Article number174903
JournalThe Journal of chemical physics
Issue number17
Early online date5 May 2023
Publication statusPublished - 7 May 2023


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