Resolution crystalline peak

DEAE-cellulose column was further purified on Sephadex G-200 but resisted all efforts at crystallization. Figure 14 (4) shows the polyacrylamide gel electrophoretic pattern of crude rat liver extract with two bands, the resolution of these bands by DEAE-cellulose, and the crystalline peak I preparation. The crystalline enzyme had an approximate molecular weight of 100,000 estimated by sucrose density gradient... 

We will now consider three cases where satisfactory peak resolution was much more difficult to achieve. Case (a), a specimen of PET fibre used for texturising, having poorly defined crystalline peaks and possibly an additional peak due to an intermediate phase (11) case (b), a specimen from a range of PET fibres with different shrinkages (.12.), again an additional intermediate phase peak was a possibility case (c), cold drawn polypropylene fibres (13). an additional paracrystalline peak was most likely here. 

Because of the possibility that an intermediate phase exists in PET, see Case (b), the resolution was carried out with four peaks and zero background parameters. Eventually, and only after several attempts, a good fit was found with three crystalline peaks, one very broad noncrystalline peak, and a polynomial background. On adding the broad peak to the new background, an identical result to that of Figure 6 (Table III) was obtained, casting doubt on the existence of a true intermediate phase. 

Figure 7. Crystalline peak resolution. Corrected and smoothed equatorial trace of a PET fiber specimen resolved into three crystalline peaks, 010, 110, 100, and...

Resolution of polyester specimen PET 06 into three crystalline peaks, and three crystalline peaks and a paracrystalline peak... 

Figure 11. Good resolution with constrained optimization and addition of a paracrystalline peak. Corrected equatorial trace of a polypropylene fiber specimen cold drawn X-5.5. Total theoretical trace now comprised of realistic crystalline peaks 110, 040, 130, 111, 131, 041, and paracrystalline peak at 15.5°. Compare...

GID and GOD data taken for very shallow angles, i.e. Oi = 0.10° and = 0.11°, have been used to determine the crystalline stmeture of nanocrystallites. Using GID at the high-resolution beamline IDIOB, several crystalline peaks of the film become visible due to the strong reduction of the substrate scattering. As shown in Figure 10.4 at least 9 sharp reflections are visible for the thickest sample (t 200 nm). 

There are several practical techniques for the determination of crystallinity. The peak resolution method is based on the approach of Hermans and Weidinger (1950) which was used on cellulose. A 20 scan including the intensive crystalline peaks and the amorphous halo is made. The diffractogram of the semicrystalline polymer consists of sharp Bragg reflections of the total intensity and an amorphous halo with a total scattered intensity I. The mass crystallinity (loj is determined from the following equation ... 

Four major computational steps are necessary to separate the individual peaks and the different profile-broadening components (i) correction and normalisation of the diffraction data, (ii) resolution of the total peak scattering from the so-called background scatter, and resolution of crystallographic, para-crystalline, and amorphous peaks from each other, (iii) correction of the resolved profiles for instrumental broadening, (iv) separation of the corrected profiles into size and distortion components. In this paper we will discuss these steps in turn, but most attention will be paid to the hitherto largely neglected step of profile resolution. 

Resolution of cold drawn polypropylene specimens into crystalline and paracrystalline peaks... 

Peak resolution is usually easier if well chosen background parameters are input and if constrained optimization methods are utilised. Misleading results can be obtained if the constraints are too limited and tests with unconstrained optimization are desirable if at all possible. In particular, the possible presence of paracrystalline or intermediate phase peaks must be tested with extreme care in order to avoid ambiguity. It is not sufficient to have a good mathematical resolution alone, all peaks must be significant in crystallographic or structural terms. The incidental measurement of peak-area crystallinity is considered to be of secondary importance to the resolution of overlapping peaks. 

The structure of the crystalline polymer was thoroughly examined and documented (158—160). High resolution nuclear magnetic resonance spectra showed only two sharp peaks characteristic for the CH3- and... 

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