References of "Baller, Jörg 50000565"
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See detailOn the Influence of Nano-Scaling on the Glass Transition of Molecular Liquids
Krüger, Jan-Kristian UL; Holtwick, R.; le Coutre, Andre et al

in Nanostructured Materials (1999), 12(1), 519-522

The nature of the glass transition is still a matter of debate. We used temperature modulated DSC (TMDSC) and Brillouin spectroscopy ( BS ) to investigate the freezing behaviour of canonical glasses ... [more ▼]

The nature of the glass transition is still a matter of debate. We used temperature modulated DSC (TMDSC) and Brillouin spectroscopy ( BS ) to investigate the freezing behaviour of canonical glasses ( salol and di-n-butyl-phtalate (DBP)) confined to controlled pore glasses (CPG) with pore diameters between 2.5 and 20 nm. The temperature behaviour of the heat capacity of the composite system deviates from the bulk fluid properties and we interpret the remaining kink-like anomaly at Tg as a static glass transition. In smaller pores Tg is only slightly shifted to lower temperatures. This operative Tg is in good agreement with sound velocity data showing a sharp kink at Tg. The working hypothesis of the existence of a static glass transition is supported by the fact that the -relaxation process disappears with decreasing pore diameter. [less ▲]

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See detailSurface-induced organization of linear molecules on nanostructured polytetrafluoroethylene: Crystalline state of poly[vinylidenefluoride-trifluoroethylene].
Krüger, Jan-Kristian UL; Heydt, B.; Fischer, C. et al

in Physical Review. B, Condensed Matter and Materials Physics (1997), 55(6), 3497-3506

Highly crystalline and uniaxial-oriented polytetrafluoroethylene films, nanostructured in one dimension, were used to produce a fully crystalline, thermoreversible morphology in the ferroelectric ... [more ▼]

Highly crystalline and uniaxial-oriented polytetrafluoroethylene films, nanostructured in one dimension, were used to produce a fully crystalline, thermoreversible morphology in the ferroelectric copolymer poly[vinylidenefluoride-trifluoroethylene]. The resulting state is built up of regularly stacked lamellar crystals of about 100 nm thickness and lateral dimensions of about 6 μm. [less ▲]

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See detailPhases and phase transitions of KPF6
Huber, P.; Krummeck, H.; Baller, Jörg UL et al

in Ferroelectrics (1997), 203(1), 211-219

Potassium hexafluorophosphate KPF6 has been investigated by X-ray powder diffraction, calorimetry and Brillouin spectroscopy. With decreasing temperature, the crystal shows a sequence of phases: NaCl-type ... [more ▼]

Potassium hexafluorophosphate KPF6 has been investigated by X-ray powder diffraction, calorimetry and Brillouin spectroscopy. With decreasing temperature, the crystal shows a sequence of phases: NaCl-type cubic-monoclinic-monoclinic with two-phase coexistence regions in between. In the cubic phase the elastic constants have been determined. c44 and c12 show a slight softening. [less ▲]

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See detailSecond-order elasticity of liquid crystals within their nematic state at high frequencies
Krüger, Jan-Kristian UL; Grammes, C.; Jiménez, R. et al

in Physical Review. E : Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics (1995), 51(3), 2115-2128

Within this work we present Brillouin and ultrasonic investigations performed on the liquid crystals p-methoxybenzylidene p-(n-butylaniline) (MBBA), p-azoxyanisol (PAA), 4-cyano-4-n-alkylbiphenyles (nCB ... [more ▼]

Within this work we present Brillouin and ultrasonic investigations performed on the liquid crystals p-methoxybenzylidene p-(n-butylaniline) (MBBA), p-azoxyanisol (PAA), 4-cyano-4-n-alkylbiphenyles (nCB), and 4-n-pentoxybenzylidene-4'-n-octoaniline (5O.8). Special attention has been paid to the evolution of a significant splitting of the two longitudinal polarized acoustic modes within the nematic phase. Angle-resolving Brillouin spectroscopy allowed the determination of the complete stiffness tensors and hence a discussion of the propagation of quasitransverse polarized acoustic modes in the nematic state of liquid crystals. We analyze the behavior of the eigenvectors of the relevant acoustic modes and discuss their significance for the propagation of quasishear modes. For 5O.8 we report an acoustic instability within its nematic state. We confirm the existence of a universal thermal relaxation mechanism of weak activation energy for the nematic state of classical liquid crystals. The observed hypersonic anisotropy is discussed in terms of that relaxation mechanism and is compared with that of glass-forming liquid crystals. [less ▲]

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See detailUniversal relaxation behavior of classical liquid crystals at hypersonic frequencies.
Grammes, C.; Krüger, Jan-Kristian UL; Bohn, K.-P. et al

in Physical Review. E : Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics (1995), 51

Within this work we present comparative Brillouin and ultrasonic investigations of p-methoxybenzylidene p-(n-butylaniline), p-azoxyanisol, and 4-cyano-4’-pentyl-biphenyl performed in the vicinity of the ... [more ▼]

Within this work we present comparative Brillouin and ultrasonic investigations of p-methoxybenzylidene p-(n-butylaniline), p-azoxyanisol, and 4-cyano-4’-pentyl-biphenyl performed in the vicinity of the nematic-isotropic transition. We confirm the existence of a universal hypersonic relaxation mechanism of weak activation energy and a related significant splitting of the two principal longitudinal acoustic modes within the nematic phase. Brillouin refractometry is proposed as a method to determine the magnitude of the nematic order parameter simultaneously with the second-order elastic stiffness constants. The origin of the hypersonic anisotropy is discussed in terms of thermal relaxations and the evolution of the nematic order parameter. [less ▲]

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