Relaxations in confinement as probed by solvation dynamics

Abstract
Solvation dynamics data of the probe quinoxaline in the glass-foxming liquid 2-methyltetrahydrofuran (MTHF) is employed to study the orientational dynamics of a liquid which is geometrically confined by porous glasses. In order to discriminate pure confinement from interfacial effects, we compare in detail the relaxation results obtained in pores with native and silanized glass surfaces with those for the bulk liquid. For the present case of highly viscous MTHF near T_g, the molecular orientation in silanized pores is almost identical to that observed in the bulk liquid. This indicates that confinement effects remain small and that the interfacial interaction between liquid molecules and the pore wall can dominate and are strongly affected by the surface chemistry. We also demonstrate how solvation dynamics techniques can be used to measure the dynamics selectively at the interface.