Geometric effects in the dynamics of a nonwetting liquid in microconfinement: An optical Kerr effect study of methyl iodide in nanporous glasses

Optical Kerr effect spectroscopy has been used to study the orientational dynamics of liquid methyl iodide in bulk and confined in nanoporous glasses of several different pore sizes. Consistent with the behavior of other nonwetting or weakly wetting liquids, the decays of confined methyl iodide are described well by the sum of two exponentials, the faster of which has the same decay rate as the bulk liquid. The slower exponential is interpreted as arising from the hindered reorientational dynamics of liquid molecules on or near the surfaces of the pores. The rate of surface reorientation depends significantly on the pore diameter, which along with other evidence suggests that the retardation of surface dynamics arises through geometric effects.