Solid-echo spectra

Fig. 13. Calculated 2H solid echo spectra for log-Gaussian distributions of correlation times of different widths. Note the differences of the line shapes for fully relaxed and partially relaxed spectra. The centre of the distribution of correlation times is given as a normalized exchange rate a0 = 1/3tc. For deuterons in aliphatic C—H bonds the conversion factor is approximately 4.10s sec-1...

Figure 14.3 Deuterium solid-echo spectra of unfilled (a) and filled (b) polyfdimethylsiloxane] networks at 305 K with and without mechanical stress as given by the parameter X [23]. This example demonstrates the sensitivity of the NMR lineshape and thus of the spin interactions to internal and external conditions...

It has been usually argued that the NMR fine-shape reaches the solid-state, rigid-lattice limit at temperatures around Tg (cf. Fig. 38), and consequently no dynamical effects are expected when measuring solid-echo spectra. While such... 

The influence of hydrophilic Aerosil on the chain dynamics in the adsorption layer becomes evident with the help of comparison of solid-echo spectra for a series of filled PDMS samples containing different amounts of Aerosil as shown in Fig. 3 [21]. 

Fig. 3. Three fully relaxed solid-echo spectra for mixtures of PDMS containing (a) 40 (149 phr), (b) 60 (336 phr), and (c) 89 (1813 phr) vol% of hydrophilic Aerosil (380 g ) [21] spectra containing a very weak broad component are also...

Thus, the H relaxation experiments and the analysis of the solid-echo spectra show that the adsorption of PDMS chain units on the surface of hydrophilic Aerosil significantly restricts the motion of chain tmits adjacent to the filler surface. However, chain units in the adsorption layer are not rigidly linked to the surface of Aerosil at temperatures well above the Tg. Motions of chain units in the adsorption layer become less restricted as the temperature increases. 

The Ti relaxation in this sample is characterized by two relaxation times, which indicate the dynamical heterogeneity of the sample. In order to assign the two T components to the chain units inside and outside the adsorption layer, solid-echo spectra at different stages of T] relaxation have been... 

Fig. 5. Partially relaxed solid-echo spectra of filled PDMS containing 60 vol% of hydrophilic Aerosil (380 g" )...

Fig. 11. A compai ison of selected experimental solid echo spectra of 8 at 28 K (middle column) with the best fit theoretical spectra obtained using the DQR (left column) and AB model (right column). In the AB fits, the amplitudes of the peak in the centre are systematically overestimated. At this temperature, the value of k,/k = c — 1.95 was obtained in the DQR fit. (Reproduced from Ref. 51. Copyright, 2001, with permission from Elsevier).

Recently, some of the methyltriptycene derivatives were re-investigated with use of the methodology of Ref. 51 (Section 4.2) to line shape analysis. In these liquid-phase studies, instead of the solid echo spectra, the Carr-PurceU (CP) echo spectra were... 

Equation (3.2.14) is the starting point for numerical simulation of dynamic wideline NMR spectra. With the Jeener-Broekaert echo the imaginary part of the exponential depending on h is measured, and with the stimulated echo the real part is measured. The lineshapes of solid-echo spectra follow from (3.2.14) with t , = 0. 

Fig. 24. Variable-temperature experimental and simulated dynamic MAS NMR (left) and H-solid echo spectra (right) for a bulk loading of two adsorbed benzene molecules per Ag-Y zeolite supercage. The numerical values accompanying the simulated MAS C-NMR spectra are the centers of a 1.9 decade EWHM log-normal rate distribution, which was varied to obtain the simulations. (Reprinted with permission from Ref. 626. Copyright 1999 American Chemical Society.)...

The network structure of unfilled and filled elastomers was probed by the analysis of the quadrupolar splitting in H solid echo spectra of uniaxially strained samples (55) (see Fig. 6). The local chain order at a given elongation is larger by a factor of 1.5-2 in the filled system. A decrease of local chain mobility in the absorption layer is observed under stress. The same method was applied to investigate molecular dynamic in thermoplastic elastomer based on hydrogen bonding complexes (61,62). 

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