Dynamics of H-bonded liquids confined to nanopores

Broad-band dielectric spectroscopy ($\rm 10^{-2}\; Hz$–$\rm 10^7\;Hz$) is employed to study the molecular dynamics of three low-molecular-weight glass-forming H-bonded liquids being confined in (dielectrically inactive) porous glasses with pore sizes of 2.5 nm, 5.0 nm and 7.5 nm. From the relaxation time distribution of the dielectric spectra, a three-layer model is deduced, consisting of molecules having solid-like, interfacial and bulk-like dynamics, respectively. The quantitative analysis of the different contributions shows that the bulk-like fraction scales with the pore size, the interfacial and solid-like layers remaining relatively unchanged. Our results restrict the possible existence of cooperatively rearranging clusters in the system below nanometer scale