Spin diffusion Goldman-Shen experiment

In this section 10.2, we review the various solid-state NMR methods used to investigate interpolymer interactions, molecular motion and the spatial structure of a polymer blend. An interaction between component polymers affects the chemical shifts and lineshapes (see Section 10.2.2.1) and the molecular motions of the component polymers (see Section 10.2.2.2). In Section 10.2.3.1, microheterogeneity from 2 to 50 nm is studied by measuring spin diffusion indirectly from its effects on H spin-lattice relaxation. The spin-diffusion processes can also be monitored by several methods based on the Goldman-Shen experiment [8] (see Section 10.2.3.2). Homonuclear and heteronuclear two-dimensional correlation experiments reveal how and to what extent component polymers interact with each other (see Section... 

Fig. 10.11. (a) Pulse sequence for the modified Goldman-Shen experiment with detection and (b) plots of H magnetization change versus square root of the spin-diffusion time for PVPh/PEO = 58/42 at 310 K. Straight lines are drawn through the initial linear portion of the data to determine the intercept time L. (Reprinted with permission from Ref. [34]. 1992 American Chemical Society, Washington, DC.)... 

Fig. 10.22. Plots of normalized deviations from the sample-averaged proton polarizations (per spin) for nylon and PBZT protons in nylon/PBZT-40/60. MP refers to the multiple-pulse version of the spin-diffusion experiment (the modified chemical-shift selective Goldman-Shen experiment) PLS indicates the proton lineshape version (the T2-selective Goldman-Shen experiments with C detection). (Reprinted with permission from Ref. [82]. 1990 Huthig Wepf Verlag.)...

Solid state proton line shape experiments on PMP and Goldman-Shen proton spin diffusion experiments on PMP were performed on a Bruker MSL 300. The 900 pulse width was typically 2 is. The Goldman-Shen experiments were performed at a temperature of 350 K with a discrimination time of )ps. 

Figure 4 Schematic rf pulse representation of the slightly modified Goldman-Shen experiment to monitor proton spin diffusion between two domains of dissimilar mobility via high-resolution detection of carbon-13 signals. The dipolar dephasing delay (xi) was fixed at 15 ps, the spin-diffusion mixing period (12) was either 0.01 ps or 10 ms, and the iH-i3C cross-polarization contact time was 100 ps.

NMR is particularly suited for the measurement of domain sizes in the range of 5 - 20oA (145), which can be probed with a spin diffusion experiment, e.g., Goldman-Shen sequence (146) and dipolar filter pulse sequence (147). The use of multidimensional techniques to study length scales in heterogeneous polymers has been previously reviewed by Spiess (148). 

A recent example from the literature which is particularly illustrative of this approach is the so-called WISE experiment [137], in which the lineshape is detected as a function of chemical shift in a two-dimensional experiment. This sequence has also been modified to permit observation of the effects of spin diffusion in what is essentially a heteronuclear two-dimensional variant of the Goldman-Shen type experiment. This has allowed clear observation of the effects of micro heterogeneity in compatible blends of PS/PVME. 

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