Transition temperature shift spectroscopy

On the basis of the calibration by melting points and phase transitions, a number of shift thermometers have been developed for solid-state NMR spectroscopy in various temperature ranges. Wehrle et al. 144), for example, used the line splitting in the N CP/MAS NMR spectrum of the organic dye molecule tetra-methyldibenzotetraaza annulene (TTAA) in the temperature range 123—405 K. A high-temperature shift thermometer for temperatures of up to 790 K was developed by van Moorsel et al. 40) on the basis of Sn MAS NMR spectroscopic... 

A similar measurement, based on molecular spectroscopy, has been made with a pre-heated test limiter in TEXTOR [59,60]. This case, with high flux densities, also shows a transition from molecules to atoms with increasing surface temperature as indicated also in Fig. 1.11. Compared to the beam experiments, the transition temperature is shifted by some 100 K. 

Does a shift of the glass transition temperature reflect a change in the relaxation time distribution or in its mean value only This makes a fundamental difference underlining the power of microscopic techniques like Broadband Dielectric Spectroscopy. 

The results published for the shift of the glass transition temperature range for freestanding PS films between -70K (thickness 20nm) as measured by ellipsometry ° and OK (thickness 20 nm) as measured by atomic force microscopy (AFM)-based shear modulation spectroscopy or ellipsome-try and The situation is similarly puzzling for... 

The purpose of this chapter is to review the application of Mossbauer spectroscopy to the study of dynamics. The main emphasis will be on the new areas in which significant advances have been made in recent years, such as the study of diffusive processes, the influence of motion on lineshape, time-dependent studies and dynamics at phase transitions. Rather less attention will be devoted to areas such as /-factors in solids, the Goldanskii-Karyagin effect and temperature shift, which have been studied more extensively in the past. The trends towards future areas for this research will also be considered, together with an evaluation and comparison between Mossbauer spectroscopy and other methods for investigating these phenomena. 

Polymer-polymer interactions in the bulk state have been studied by a number of experimental tools see Table 4.4. For phase-separated compositions, dynamic mechanical spectroscopy (Chapter 8) measures shifts in the glass transition temperature, which provides a measure of the extent of molecular mixing in partially mixed systems. Electron microscopy is used to determine domain size and shape see Section 4.5.6 (50-52). 

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