Stick-type spectrum

Fig. 21. (a) CP/MAS 13C NMR spectrum of poly(tetramethylene oxide) at 0 °C. (b) The partially relaxed spectrum. (c) Stick-type spectrum in CDCI3 at room temperature... 

Fig. 25. DD/MAS 13C NMR spectrum of isotactic polypropylene at different temperature with stick-type spectrum in solution...

Figure 1 shows a 50 MHz CP/MAS C NMR spectrum of ramie cellulose and a stick-type nmr spectrum of low molecular weight cellulose( DP <10) In deuterated dimethyl sulfoxide solution(DMSO) (8 ) (The broken and solid lines In the CP/MAS spectrum will be explained below.). As already reported(9,10), the assignments for the Cl, C4 and C6 carbons are relatively easy, based on analogies with the solution state spectrum. However, It should be noted that these resonance lines shift downfleld by 2.3-9.6 ppm In the solid state compared to the solution state. The cause of such large downfleld shlfts(to be explained In the next section) Is attributed to the different conformations about the P-l,4-glycosldlc linkage and the exo-cyclic C5-C6 bond in which these carbons are Involved. 

Figure 1. 50MHz CP/MAS HMR spectrum of ramie and stick-type scalar-decoupled HMR spectrum of low molecular weight cellulose In DMS0-d5 solution (.8). Broken and thin solid lines In the CP/MAS spectrum are for the crystalline and noncrystalllne components, respectively.

Figure Bl.16.22 shows a stick plot siumnary of the various CIDEP mechanisms and the expected polarization patterns for the specific cases detailed in the caption. Each mechanism clearly manifests itself in the spectrum in a different and easily observable fashion, and so qualitative deductions regarding the spin multiplicity of the precursor, the sign of Jin the RP and the presence or absence of SCRPs can innnediately be made by examining the spectral shape. Several types of quantitative infonnation are also available from the spectra.

Figure 3. Low field wing of ESR spectrum of Na+N- in THP at 27°C. a In the absence of glyme b In the presence of 0.006M tetraglyme c Stick model showing both types of ion pairs.

For positrons and Ps in polymeric surfaces, one needs to consider three additional important effects in addition to the bulk (1) the diffusion of the positron and Ps back to the surface, (2) the formation of Ps from the positrons by abstracting the surface electron, and (3) the Ps emission to the vacuum from the surface or the sticking of Ps on the polymeric surfaces. The dynamic behavior of the positron and Ps near the surface is schematically shown in Figure 11.2 below. The lifetimes of the positron and of Ps are different among those three types in addition to that of the bulk. If each has one distinct lifetime, a typical PAL lifetime spectrum could contain eight lifetimes for a complete analysis. This is beyond the current resolving power of the PAL data analysis method, either discrete or continuous. A practical approach is to invoke some good theoretical models before one applies the conventional data analysis method to a PAL spectrum near the surface for polymeric materials. 

UPEOC was Y-irradiated up to 2.8 Mrad and ESR spectra of the produced radicals were observed under various conditions. Though a detailed discussion of the observed spectra must be omitted here, a stable spectrum observed after the heat treatment at room temperature was identified as coressponding to the free radicals CHj—CH—O—CHj. The stable spectrum observed at 293 K is shown in Fig. 5.4. in which a stick diagram explains the afore-mentioned identification. This stable radical is a secondarily produced radical originating from a scission-type radicaF, CH -CHj-O-CHj. 

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