DD/MAS spectra

Figure 22 shows the Ala Cp peak in a time series of DD/MAS and CP/MAS spectra. Within lOOhours from the start, DD/MAS spectra show a Cp peak whose... 

Figure 15 (A) C H CP/MAS NMR spectra and (B) DD/MAS spectra of dry (black) and wet, supercontracted C/ N-enriched spider dragline silk. A CP time of 1 ms was used, and the DD experiment was performed with a 1-s recycle delay. Reproduced from [173] with permission of The Royai Society of Chemistry.

An example for the polymer network characterization by the 13C CP MAS NMR is shown in Fig. 35. The chemical structure of the cured polystyrylpyridine resins (PSP), synthesized from terephthalic aldehyde and collidine (2,4,6-trimethylpyridine), is determined from CP-MAS spectra by comparison with the solution state spectra of the model compounds and supported by selective DD observations. The CH and CH2 of the crosslinking points, as deduced from the model BP2, give rise to a composite line at about 45 ppm the assignment of other signals is indicated in the figure 239). 

Fig. 14. DD/MAS 13C NMR spectra of different polyethylene samples crystallized under high pressure, obtained by a n/4 single pulse sequence [ti/4-FID-t ] (a) Fraction 1, (b) Rigidex 9, (c) HO20-54P, (d) Hifax. The repetition time x( is indicated in each spectrum...

Fig. 16. 50 MHz DD/MAS 13C NMR spectra of highly drawn polyethylene samples with different draw ratios, obtained by a tt/4 single pulse sequence (7i/4-FID-3Tlc)...

Phase structure. It was confirmed in the previous section that the bulk iPP crystal consists of three phases the crystalline, noncrystalline amorphous phase and crystalline-amorphous interphase. Hence, it is also assumed that the bulk sPP crystal forms a three-phase structure in a similar manner. The question here is whether the sPP crystal involves such a phase structure in forming a gel or not In order to study this problem, we have analyzed 13C NMR spectra of the sPP gel. The noncrystalline contributions to each resonance of CH2, CH and CH3 carbons in the DD/MAS 13C NMR spectrum of the gel can be seen, as indicated by the arrows in Fig. 27, where their assignment as noncrystalline resonances was confirmed by the spin-lattice and spin-spin relaxation times as described above with relation to the results in Table 13. We carried out the line-decomposition analysis of the resonance lines of the methine and methyl carbons, since these resonances are most pertinent for the present purpose because of the simplicity of the spectral shape. 

DD/MAS NMR Spectra. Figure 16 shows the equilibrium NMR spectra of those samples that were obtained by the pulse sequence (Ti/4-FIDDD-3Tic)n at room temperature. Here the sample A is the undrawn dried gel, B is the sample obtained from A by annealing at 145 °C for 4 minutes, and C, D, and E are samples drawn 50,100, and 50 times, respectively. For most spectra there is a recognized downfield resonance at ca. 33 ppm assignable to the orthorhombic crystalline component and an upheld resonance at ca. 31 ppm assignable to the noncrystalline component. 

Fig. 13. " Si CP/MAS (a) and - Si DD/MAS NMR (b) spectra of PDPhSM at room temperature. The signal corresponding to the non-crystalline region is indicated by an asterisk.

Fig. 15.2.27. " C MAS spectra of DGEBA-DDS with 100% stiochiometry (a) 23°C with cross-polarisation and (b) 290°C without CP (c) expanded.

Figure 21.3 shows the methyl resonance region of the 67.9 MHz DD/MAS NMR spectra of P(3HB) and P(3HB-co-3HV) samples. Each of the 3HB and 3HV methyl resonances was resolved into two peaks contributed from the crystalline and amorphous phases, respectively. Hence, from these measurements, the relative contributions from the crystalline and noncrystalline regions can be quantitatively estimated. The resulting chemical shifts and the relative peak intensities are listed in Table 21.2. 

Table 21.2. Chemical shifts and peak intensities of methyl carbon resonances in DD/MAS NMR spectra... 

Clearly, both the C CP-MAS and DD-MAS NMR spectra of [3- C]Ala-bR resonating at 14-18 ppm arise from at least seven resolved C NMR signals. The individual peaks are ascribed to the portions of the transmem-... 

In contrast, the DD-MAS NMR spectra of the [l- C]-amino acid (Ala, Leu, Val, etc.)-labeled bR detect signals only from the residues at the flexible surface area as illustrated for [l- C]Ala-bR in Fig. 24.18, whereas the CP-MAS NMR spectrum is selectively able to detect signals from the transmembrane helices and loops [76]. This distinction simply arises from the fact that the Tj valuses of the 1- C carbons in the N- or C-terminus and... 

Table 2 shows the results obtained by CP/MAS, DD/MAS and dipolar-dephasing CP/MAS measurements. Assignment and analysis of the spectra were followed as in past work.100 It is found that the results for raw coal and coal heated at 104 °Cmin-1 are in accord with each other. A similar tendency is found with the results of all three types of NMR measurements. When... 

Fig. 7. I3C CP-MAS NMR (upper traces) and DD-MAS NMR spectra (lower traces) of l tC=0, Ca and Cp carbons from [ 1,2,3-13C3]Ala-labeled bacteriorhodopsin.81 Reproduced with permission from the Japanese Biochemical Society.

---