TY - JOUR A1 - Frunza, L. A1 - Kosslick, H. A1 - Pitsch, I. A1 - Frunza, St. A1 - Schönhals, Andreas T1 - Rotational Fluctuations of Water inside the Nanopores of SBA-Type Molecular Sieves N2 - The rotational molecular dynamics of water confined to nanoporous molecular sieves of a regular hexagonal (SBA-15) and of a foamlike pore structure was studied by dielectric spectroscopy in the frequency range from 10-2 to 109 Hz and in a broad temperature interval. Two relaxation processes were observed: the process at lower frequencies is related to water molecules forming a layer, which is strongly adsorbed at the pore surface, whereas the relaxation process at higher frequencies is assigned to fluctuations of water molecules situated close to the center of the pore. The relaxation times of the low-frequency process for both materials and of the high-frequency process for the SBA-15 material have an unusual saddlelike temperature dependence, reported here for the first time. To describe this temperature dependence, a model developed for water confined to nanoporous glasses by Ryabov et al. [J. Phys. Chem. B 2001, 105, 1845] was applied, which considers two competing effects. The characteristic features of these two competing processes were compared with those reported for other porous systems. PY - 2005 DO - https://doi.org/10.1021/jp044503t SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 VL - 109 IS - 18 SP - 9154 EP - 9159 PB - Soc. CY - Washington, DC AN - OPUS4-7611 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -