Peculiar Solvent Flow along the Gel Network after Gelation at Interfaces

Area of Science:

• Physical Chemistry
• Materials Science
• Surface Science

Background:

• Miscible liquid mixtures can exhibit non-uniform spatial distributions when gelled at interfaces.
• Understanding solvent behavior at solid-liquid interfaces is crucial for materials design and processing.

Purpose of the Study:

• To map the spatial distribution of solvents within a gel near solid surfaces.
• To investigate the influence of surface wetting on solvent distribution in a gelled binary mixture.

Main Methods:

• Confocal Raman microscopy was employed to visualize solvent concentrations.
• A binary mixture of p-xylene and octanenitrile was gelled in contact with various solid surfaces.

Main Results:

• An excess of p-xylene was observed near completely wet surfaces shortly after gelation.
• The p-xylene concentration excess decreased linearly with distance from the surface, extending up to 200 μm.
• This excess distribution was kinetically stable, relaxing to a uniform state over approximately 10^4 seconds.

Conclusions:

• The observed solvent distribution is explained by hydrodynamic theory, involving solvent flow along the gel network.
• The flow is driven by a balance between spreading flux from the adsorbed layer and outward diffusion.