Critical effect of pore characteristics on capillary infiltration in mesoporous films

International audiencea Capillary phenomena governing the mass-transport (capillary filling, condensation/evaporation) has been experimentally investigated in around 20 different silica thin films exhibiting various porosities with pores dimension ranging from 2 to 200 nm. Films have been prepared by sol–gel chemistry combined with soft-templating approaches and controlled dip coating process. Environmental ellipsometric porosimetry combined with electronic microscopy were used to assess the porosity characteristics. Investigation of lateral capillary filling was performed by following the natural infiltration of water and ionic liquids at the edge of a sessile drop in open air or underneath a PDMS cover. The Washburn model was applied to the displacement of the liquid front within the films to deduce the kinetic constants. The role of the different capillary phenomena were discussed with respect to the porosity characteristics (porosity vol%, pore dimensions and constrictions). We show that correlation between capillary filling rate and pore dimensions is not straightforward. Generally, with a minimum of constrictions, faster filling is observed for larger pores. In the case of mesopores (