Solvation dynamics of molecular glass-forming liquids in confinement

Triplet state solvation dynamics experiments on geometrically confined glass-forming liquids are performed in order to study the effects of confinement on length scales of several nanometres. Variations of the surface chemistry of porous glasses and the spatially selective observation of the interfacial liquid layer indicate that the surface interactions determine the difference between the dynamics of the bulk and confined situations. For 3-methylpentane in pores of 7.5 nm diameter, the timescale of interfacial dynamics is slowed down by three orders of magnitude, while structural relaxation already remains bulk-like just a few nanometres away from the silica surface. The time-resolved optical linewidths indicate dynamical heterogeneity in confined liquids, but the signature differs from the bulk case.