Magic angle spinning techniques

In order to study the cure behavior of the PTEB system, 1JC NMR of uncured and cured PTEB in the solid state was performed using crosspolarization magic-angle spinning techniques. The results show the polymerization to be via aromatization. The extent of cure versus cure temperature was determined quantitatively. It was found that the material was almost completely cured after one hour at 215°C. As the cure goes to completion, the ability to react decreases due to the corresponding rapid increase in Tg. Chemical shifts of the resonances in the cured material are consistent with a highly crosslinked condensed aromatic network. 

We can successfully measure 170 MAS NMR spectra of poly(L-Ala)s using high-field and high-speed magic-angle spinning technique. From the 170 MAS spectra three kinds of NMR parameters such as chemical shift, quadrupolar coupling constant and asymmetric parameter were obtained exactly and understood the relationship... 

The basic spectrometer we have employed for the study of solid polymers by cross-polarization/magic-angle spinning techniques is a Nicolet TT-14 pulse-FT system operating at 1.4T with resonance frequencies of 15.087 MHz, 60.0 MHz and 56.4 MHz for 1r and... 

High-resolution NMR in solution requires the sample to be soluble in a solvent such that the various nuclear spin interactions can be averaged or removed by molecular micro-Brownian motions. Unfortunately, elastomers used in various applications are normally crosslinked materials and therefore not soluble in any solvent. Thus, solid state NMR with magic angle-spinning technique has been used with great success in the study of cured elastomers. However, this technique demands extended instrument facilities and expertise. 

Obviously, the magic angle spinning techniques described briefly above rely on coherent averaging out of resonance line-broadening interactions. An alternative approach is to cause solids to assume the incoherent motion of molecules in the liquid phase. Essentially, two such methods exist. The first is the so-called ultra-fine particle NMR (UFPNMR) method which was proposed originally by Yesinowski [21 ] and developed further by Kimura [22,23]. The second is the sonically induced narrowing of the NMR spectra of solids (SINNMR) that was demonstrated recently by Homer et al. [24,25]. 

Fig. 6. NMR spectrum of Si in a-Si H as obtained using cross polarization and magic angle spinning techniques. The numbers represent a suggested decomposition into five separate contributions. [From Lamotte et al. (1981b).]...

Solid-state NMR spectra were observed using the cross-polariza-tion/magic angle spinning technique on a Bruker CXP-300 spectrometer operating at 7 T. Contact time, repetition time and high... 

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