Meridional scattering

The meridional scattering curve of intrinsic crazes has not been analyzed in detail. However, it may be worth mentioning that this scattering component continuously increase up to very high intensities at small reciprocal vectors. The same type of scattering behavior has previously been reported for extrinsic crazes J. Brown and Kramer assumed that internal reflections at the craze-matrix boundary strongly contribute to the intensity measured along the meridian. 

An important feature of the diffraction pattern predicted by these models is the occurrence of a series of meridional reflections which are orders of a 10.33 A periodicity. This periodicity is associated with the axial projection of the asymmetric unit, which consists of seven residues. Astbury and Bell (1939) had noted such a periodicity in a-keratin and given spacings for the first four orders, whereas a spacing of 1.49 A, close to the seventh order, had been noted by MacArthur (1943). More recently, meridional scatter in the vicinity of the fifth, ninth, and eleventh orders has been reported (Fraser and MacRae, 1961b). In a field where structural models had been considered plausible if they predicted one reflection the suggestion of the coiled-coil models was thus a very significant advance. 

SAXS pattern of radiation-polymerized PTOX in Figure 3A shows only a sharp equatorial scattering, but no meridional scattering. Those for PTOX obtained by plasma initiated polymerization (samples PTOX-20-1P and PTOX-40P shown in Figures 3B and 3C) are similar. In the case of PTEOX, those polymerized through radiation initiation but post-polymerized below 80°C (sample PTEOX-12)... 

It is noteworthy that, for an oriented nematic liquid crystalline polymer, the equatorial scattering provides important information regarding the interchain correlation, while the meridional scattering represents the correlation along the chains, which in general is featureless in the experimental X-ray diffraction patterns. 

Figure 5.9 Calculated meridional scattering of one-dimensional crystal with different root-mean-square displacement a. Y axis is the intensity while X axis is the scattering vector 2qa, q = The percentage is derived from a//, and / is the length of layer that is 30 A. 

For the two-dimensional liquid, the scattering signature is similar to that of the nematic liquid crystalline polymers discussed in the previous section. It should have a diffuse equatorial scattering whose intensity is significantly lower than that of the meridional scatterings from the one-dimensional crystal. 

Figure 3.18 shows a schematic representation of double-oriented-kebab strac-ture. Stacks of parent lamellae is responsible for meridional scattering the SAXS patterns, whereas stacks of daughter lamellae exhibited equatorial scattering. The equatorial scattering is attributed to the overlap of scattering from daughter lamellae and shish. 

Figure 2.1 shows SAXS patterns of PTeOX and PTOX. PT OX post-polymerized at a temperature below 70 °C indicates no meridional scattering, which is rimilar to that of PTOX obtained at 55 °C. On the otha- hand, PTgOX obtained over 80 °C shows clear meridional as well as equatorial scattering, and the spot-like scatterings also are observed outside the broad meridional scattering. 

The meridional scattering pattern is less sensitive to heating of the sample (Figure 17). At 20-300°C (the structure of CPE is biphasic), each... 

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