Narrow component

Fig. 6. NMR lineshape for glow discharge deposited a-Si H film grown at 25°C. The top curve is the experimental data and the middle and bottom curves are the deconvolution of the data into broad and narrow components (Reprinted with permission from Reimer et al., 1981a, Pergamon Press, pic).

The area below the absorption curve is proportional to the number of protons in the sample which permits the decrease of free plasticizer to be calculated from the change of this area upon cooling. For each sample the area below the curve is constant, regardless of whether the absorption is narrow or broad. Below the glass temperature the narrow component of the absorption curve can be attributed to the plasticizer, whereas the broad component represents the glassy polymer and that part of the plasticizer which is already immobilized. 

Irradiated polyethylene exhibits different effects on the two observed broad and narrow components 26 27,28 29). The first effect of irradiation on motional behavior... 

Two component spectra of plasma polymerized styrene (PPS) observed above 50 QC were interpreted in terms of a mesh-like crosslinked network structure. Broad and narrow components are attributed to the protons in crosslinked regions and oligomeric structures (which act as plasticizers), respectively 3i). 

Recently Bergmann and Nawotki12-15) have developed a method to decompose such spectra for polyethylene into three components broad, intermediate, and narrow components. The methylene groups of the polymer were divided into three classes rigid, hindered-rotational, and micro-Brownian mobile CH2-groups, and these were... 

In the following chapters we will discuss the phase structure of linear polyethylene samples in the solid state by analyzing the broad-line proton NMR spectrum by a technique developed by Bergmann and Nawotki12-14), decomposing the spectrum into three parts broad, medium, and narrow components. We first therefore review the three-component analysis used in this series of work. 

Here, H can be conveniently expressed as the deviation of the field from the center of the resonance in gauss units H=H —H0 yb,ym, and yn are the elementary spectra of the broad, the medium, and the narrow components, respectively. These are considered to be contributed from protons belonging to the crystalline region, and hindered-rotational and micro-Brownian mobile methylene groups in the amorphous region, respectively. pb,pm, and 0n determine the line-width and breadth of the respective elementary spectra wb, wm, and iv designate the respective mass fractions. Each elementary spectrum is normalized as... 

Narrow Component. As discussed in Chapter II, the absorption spectrum for polyethylene cannot be described by a single Lorentzian even in the molten state. However, the deviation from one Lorentzian is not enhanced for well-fractionated samples in the melt and, furthermore, becomes negligible as the temperature decreases42. Accordingly, the differential form of a Lorentzian distribution can be used for the elementary spectrum of the narrow component ... 

However, since the line-width of the narrow component is generally rather small for most samples studied, the line shape is distorted by the amplitude of the modulation Hm, as pointed out already. It is well known that if the condition Hm A///5 is fulfilled, distortions due to the Hm are negligible. Since this condition is generally... 

The spectrum for samples with a very low molecular weight, ie., lower than about 1000, is fairly independent of the mode of crystallization, whether from the melt or from dilute solution. The spectrum is characterized by a very large broad component (wb 0.95) and a medium component with a large second moment, but no narrow component. In such samples the extended molecular chain length will be comparable to or slightly larger than the lamella thickness. The conformation of molecular chains to form the lamellar crystallites will be similar to that depicted schematically in Fig. 10 (B), independent of the crystallization mode. 

C for the bulk-crystallized sample, as shown in Fig. 12. A similar effect of drawing is also evident in the behavior of the narrow component, suggesting that the -relaxation process is shifted to a higher temperature with increasing draw ratio. 

For the 10-fold drawn sample the A Hn remains at a very low level, about 0.4 G, over the temperature range examined. As discussed already, the narrow component for such a highly drawn sample will be contributed mainly by protons belonging to methyl end-groups or adjacent methylene groups insensible to the macroscopic drawing. Such components will be fairly mobile even at lower temperatures. The very small value of AHn for the highly drawn sample can thus be easily understood. 

The expressions for the linewidths in a spectrum with quadrupole splittings for nuclei with I = 3/2 has been derived (13). Thus the central peak has the same linewidth as the narrow component in Equation lib. In Ref. 13 the linewidths of the two satellites have also been calculated to be ... 

Our broad-line XH NMR analysis showed that this type of sample generally consists of the phase structure of lamellar crystallites and noncrystalline overlayer with a negligible amount of the noncrystalline amorphous phase [16,62]. In broad-line H NMR spectra of solution-grown linear polyethylene samples, a narrow component that suggests the existence of a liquid-like amorphous phase is hardly recognized. In Table 2, the three-component analysis of the broad-line XH NMR spectra of linear polyethylene samples with different molecular weights that were crystallized isothermally from 0.08% toluene solution at 85 °C for 24 hours under a nitrogen atmosphere is summarized. 

The mass fraction of the narrow component that corresponds to the rubbery noncrystalline amorphous phase is as small as 0.003-0.006. The mass fraction does not increase appreciably with increasing temperature, but stays almost unchanged up to 70 °C. Hence, it is concluded that solution-grown samples do not actually comprise a rubbery amorphous phase. This conclusion is confirmed by high-resolution solid-state 13C NMR with more detailed information. 

Fig. 7.21. Angular correlation curves for mixtures of O2 and CI2 gases with an overall pressure of 120 atmospheres, (a) Pure O2, (b) O2 with 0.02 atmospheres of Cl2, (c) O2 with 0.05 atmospheres of CI2, (d) 02 with 0.2 atmospheres of CI2 and (e) O2 with 1 atmosphere of CI2. Goldanskii and Mokrushin (1968) attributed the components labelled Wi, W2 and W3 to the annihilation of thermalized para-positronium atoms (Wi, the narrow component), the annihilation of free positrons in O2 (W2) and the annihilation of positrons in the PsCl compound (W3). The intensity of the last, i.e. W3, grows progressively with the addition of CI2 to the O2 buffer.

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