Rheology and Dynamics of Simple and Complex Liquids in Mesoporous Matrices

Subject of my thesis is a study of rheologic and dynamic properties of fluids confined in an isotropic pore network with pore radii of approx. 5nm embedded in a monolithic silica matrix (porous Vycor). The experimental technique bases on the capillary rise of a wetting liquid in a porous substrate, also known as spontaneous imbibition. A crucial part of the conducted experiments centers on the increasing relevance of the liquid-substrate interface in the mesopore confinement. Detailed analyses of the measurements carried out with water, silicon oils, and a series of hydrocarbons result in precise information on the boundary conditions expressed in terms of the velocity slip length. Systematic variations of the chain-length of the used hydrocarbons also allow for an assessment of the influence of the shape of the liquid's building blocks on the nanoscopic flow behavior. Supplemental forced throughput experiments additionally address the impact of the liquid-substrate interaction. Furthermore, the influences of spatial confinement on the surface freezing transition of the linear hydrocarbon n-tetracosane as well as on the mesophase transitions of the liquid crystal 8OCB are investigated. Finally, a third, more general study focuses on the kinetics of the invasion front, which is supposed to be influenced significantly by the random environment of the pore space considered.