Experimental NMR Methodology

Multiple field data can be used to determine the dominant interaction and to provide an estimate of the quadrupole interaction even when a distinct quadrupole lineshape cannot be discerned. As an example, the linewidths of the Ti-O-Si fragments in the above amorphous gel determined at 5.6 and 14.1 T are shown in Table 6.1. 

If measurements are taken at a second magnetic field (B02) so that = (B02/B01) then the total linewidth at the second field may be written as 

measurements at the two fields allow these two contributions to be estimated, from which the quadrupole interaction can also be estimated by simulating the line derived by superposition of the two contributions. 

From van Eck and Smith (1998). C. Observed and simulated H- 0 CP echo NMR spectrum of Mg(OH)x(OCH3)2-x without using proton decoupling during acquisition. From van Eck and Smith (1998). All figures used by permission of the copyright owners. 

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Over the last 15 years, several advanced experimental NMR methodologies, in both the solution and the solid state, have been developed for the analysis of complex silicone systems, their structures, and the mechanisms of aging and degradation. As discussed above, chemical shift data and relaxation phenomena have been exploited for decades to gain insight into, e.g., the identity of crosslinks in PDMS networks, the dynamical behavior of melt-state polymer chains, correlations among physical and chemical properties of polymeric material and a variety of NMR observables, etc. While these... 

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