Cooperative motion and growing length scales in supercooled confined liquids

Using molecular dynamics simulations we investigate the relaxation dynamics of a supercooled liquid close to a rough as well as close to a smooth wall. For the former situation the relaxation times increase strongly with decreasing distance from the wall whereas in the second case they strongly decrease. We use this dependence to extract various dynamical length scales and show that they grow with decreasing temperature. By calculating the frequency dependent average susceptibility of such confined systems we show that the experimental interpretation of such data is very difficult.Comment: 7 pages of Latex, 3 figure

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