How a coating is hydrated ahead of the advancing contact line of a volatile solvent droplet.
The wettability of coatings is very sensitive to the amount of solvent they may contain. When a droplet of volatile solvent, such as water, is deposited on a substrate, its vapor may quickly condensate just ahead of the contact line. We give an estimation of the extent of solvent uptake by a coating of variable thickness e , in front of an advancing contact line of given velocity U . Depending on the values of e and U , we observe three regimes: at low velocity and for a thin coating, the coating adsorbs a fraction of solvent that can quickly equilibrate across its entire thickness, so that it mainly appears solvophilic, while this is not the case for a thick coating. For high velocities, regardless the coating thickness, the coating ahead of the contact line does not have enough time to adsorb a significant amount of solvent, so that it mainly appears solvophobic. All these phenomena appear to be controlled by a molecular cut-off length.
Tay
A
A
PPMD-SIMM, UMR, CNRS, UPMC, ESPCIParisTech, Paris, France.
Monteux
C
C
Bendejacq
D
D
Lequeux
F
F
D000178:Acrylamides / Q000737:chemistry*; D000327:Adsorption; D000465:Algorithms; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D008956:Models, Chemical; D012997:Solvents / Q000737:chemistry*; D014835:Volatilization; D014867:Water / Q000737:chemistry*; D017155:Wettability
D000178:Acrylamides; D020099:Coated Materials, Biocompatible; D012997:Solvents; C429790:poly(N,N-dimethylacrylamide); D014867:Water