98
M. Seto et al.
2.4.6 Results Obtained by Quasielastic Scattering
Experiment Using Time-Domain Interferometry
of Mössbauer Gamma Rays
So far, QEGS measurements using TDI were performed for alloys, liquid crystals, molecular liquids, ionic liquids, super-ionic conducting glasses, polymers, and
polymer nanocomposites. For supercooled glass formers, van der Waals molecular
liquid o-terphenyl, hydrogen bonding liquid glycerol, ionic liquids, and polymer
polybutadiene were measured to study the microscopic dynamics toward glass transition. In glycerol and polybutadiene, the so-called de Gennes narrowing was observed
by the q-dependent studies of the structural relaxation process called as the α-process
[128]. In addition to the α-process, a local activation process called as the JohariGoldstein (JG) β-process was observed in o-terphenyl and polybutadiene [124, 128].
The branching temperature of the JG β-process from the α-process, which could
not be determined by conventional methods, such as dielectric spectroscopy, was
accurately obtained. The study of ionic liquid 1-butyl-3-methylimidazolium iodide
revealed that the ionic liquids are classified as so-called fragile glass formers [125].
For superionic conducting Na 3 PS 4 glass, it was revealed that angstrom-scale translational motion of a part of Na ions occurs at picosecond to nanosecond time scale,
while the movement of PS 4 ions rarely occur [129].
To understand the microscopic origin of the shear viscosity, a higher alcohol
3,7-dimethyl-1-octanol with nanometric domain structures was studied using the
multiline TDI system [130]. The dynamics of both nanometric- and molecularscale structures were found to relate to the slower and faster relaxation modes of
the shear viscosity. The effect of the presence of Si nanoparticles on bulk polymer
(polybutadiene) dynamics was studied for a polymer nanocomposite system [131].
B2 alloy CoGa was studied using the single-line TDI, and the possibility of the
atomic diffusion study using diffuse scattering was shown [132].
For soft materials, QEGS was applied for dynamics study of liquid crystal
molecules 4-cyano-4’-octylbiphenyl and 11-(4’-cyanobiphenyl-4-yloxy) undecyl
pentadecafluorooctanoate under layered structure in the smectic phase [133]. Both
the interlayer and intralayer molecular relaxation times were successfully observed
using the multiline TDI system. The layer order parameter of the smectic phase was
determined, and the anomalous diffusion coefficient could be obtained using the
multiline TDI system [134]. The study of cholesteric blue phase revealed that the
emergence of the mesostructure is irrelevant to the microscopic molecular structure
and dynamics in this system [135]. TDI allows the study of molecular dynamics in
smectic, nematic, and cholesteric phases.
M. Seto et al.
2.4.6 Results Obtained by Quasielastic Scattering
Experiment Using Time-Domain Interferometry
of Mössbauer Gamma Rays
So far, QEGS measurements using TDI were performed for alloys, liquid crystals, molecular liquids, ionic liquids, super-ionic conducting glasses, polymers, and
polymer nanocomposites. For supercooled glass formers, van der Waals molecular
liquid o-terphenyl, hydrogen bonding liquid glycerol, ionic liquids, and polymer
polybutadiene were measured to study the microscopic dynamics toward glass transition. In glycerol and polybutadiene, the so-called de Gennes narrowing was observed
by the q-dependent studies of the structural relaxation process called as the α-process
[128]. In addition to the α-process, a local activation process called as the JohariGoldstein (JG) β-process was observed in o-terphenyl and polybutadiene [124, 128].
The branching temperature of the JG β-process from the α-process, which could
not be determined by conventional methods, such as dielectric spectroscopy, was
accurately obtained. The study of ionic liquid 1-butyl-3-methylimidazolium iodide
revealed that the ionic liquids are classified as so-called fragile glass formers [125].
For superionic conducting Na 3 PS 4 glass, it was revealed that angstrom-scale translational motion of a part of Na ions occurs at picosecond to nanosecond time scale,
while the movement of PS 4 ions rarely occur [129].
To understand the microscopic origin of the shear viscosity, a higher alcohol
3,7-dimethyl-1-octanol with nanometric domain structures was studied using the
multiline TDI system [130]. The dynamics of both nanometric- and molecularscale structures were found to relate to the slower and faster relaxation modes of
the shear viscosity. The effect of the presence of Si nanoparticles on bulk polymer
(polybutadiene) dynamics was studied for a polymer nanocomposite system [131].
B2 alloy CoGa was studied using the single-line TDI, and the possibility of the
atomic diffusion study using diffuse scattering was shown [132].
For soft materials, QEGS was applied for dynamics study of liquid crystal
molecules 4-cyano-4’-octylbiphenyl and 11-(4’-cyanobiphenyl-4-yloxy) undecyl
pentadecafluorooctanoate under layered structure in the smectic phase [133]. Both
the interlayer and intralayer molecular relaxation times were successfully observed
using the multiline TDI system. The layer order parameter of the smectic phase was
determined, and the anomalous diffusion coefficient could be obtained using the
multiline TDI system [134]. The study of cholesteric blue phase revealed that the
emergence of the mesostructure is irrelevant to the microscopic molecular structure
and dynamics in this system [135]. TDI allows the study of molecular dynamics in
smectic, nematic, and cholesteric phases.