Wide Angle X-ray Diffraction Studies

The coexisting two phases - Ff and Fnf - for these copolymers can be transformed into a single all-trans ferroelectric phase by using the following methods  

Uniaxial drawing in low VF2 content samples causes not only a molecular orientation of the material, but also a transformation of the Fnf phase into an 

Another possibility to transform the non-ferroelectric into the ferroelectric phase is by application of an electrical field [38]. Poling at room temperature causes a transformation similar to that obtained by drawing [38], However, compositions with high VF2 content which do not contain a minimum amount of disorder as that found in the melt solidified samples, show no significant improvement of molecular packing as a result of poling treatment [59,60]. 

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Bouwstra, J.A., et al. 1992. Structure of human stratum corneum as a function of temperature and hydration A wide-angle X-ray diffraction study. Int J Pharm 84 205. 

The inclusion complex formation between PEO blocks of the Pluronic copolymers and a-CD in the hydrogels was confirmed with wide-angle X-ray diffraction studies of the hydrogels [68], The effect of a-CD to aid the gelation of... 

Wide-Angle X-Ray Diffraction Studies. An interesting feature of the Nafion membranes is its ability to crystallize in spite of the long side-chain groups. The presence of crystallites in perfluorinated... 

Effect of Crystallinity. While neutralization is known to exert a strong influence on mechanical relaxations, it is conceivable that the degree of crystallinity is also significant. To explore this aspect, an amorphous Nafion salt sample was prepared by rapid quenching from the melt (40). The original Nafion salt (EW = 1200) had a degree of crystallinity of ca. 7% as revealed by a wide angle X-ray diffraction study (40). The quenched sample was also found to be completely amorphous by the absence of the crystalline diffraction peak. 

J. A. Bouwstra. G. S. Gooris, M. A. Salomons-de Vries, J. A. van der Spek, and W. Bras. Structure of human stratum comeum as function of temperature and hydra-lion. A wide angle x-ray diffraction study. Int. J. Phaim. 84 (IW2) 205-216. 

Wide angle X-ray diffraction studies on the highly drawn sheets show that the crystallographic c-axes are highly aligned parallel to the fibre axis and the easy shear therefore occurs parallel or perpendicular to the c-axes, although its exact nature is not known from these studies. 

They are designated, alphabetically, PP-A to PP-F. The densities of these films, measured at 295.2 K using an ethyl alcohol/water density gradient column, are tabulated in Fig. 1, together with a summary of the results of a qualitative wide-angle x-ray diffraction study of the crystalline orientation(s) in the films using a flat plate camera. Three diffraction patterns were recorded for each film with the x-ray beam parallel to the film normal (N), to the machine direction (M), and to the transverse direction (T). 

The wide angle x-ray diffraction study makes it clear that amphiphile molecules aggregate in a crystalline form in the composite membrane. Also, the small angle x-ray scattering investigation tells us existence of the multilamellar liposome composed of bimolecular lamellae. 

Most polyphenylquinoxalines show no crystallinity in wide-angle X-ray diffraction studies. Their amorphous nature is primarily due to the configurational disorder carried out in the backbone of the polymer chains by the presence of... 

Somani R H, Hsiao B S, Nogales A, Fruitwala H, Srinivas S and Tsou A H (2001) Structure development during shear flow induced crystalhzation of i-PP in situ wide-angle x-ray diffraction study, Macromolecules 34 5902-5909. 

A similar type of pseudo-phase diagram is shown in Fig. 5.18 for random copolymers of ethylene terephthalate (PET), and ethylene naphthalene 2,6-decarboxylate (PEN).(l 12,137) The data points corresponding to the different crystallization procedures are very close to one another. Wide-angle x-ray diffraction studies have shown that significant crystallinity is present in fibers of these random copolymers. 

Wide-angle x-ray diffraction studies of crystalline networks of both polyethylene and natural rubber show that with increasing cross-linking density there is a progressive broadening of the reflections from various crystalline planes.( 13,14,23) This broadening can be attributed to either a decrease in crystallite size, the development of ftuther imperfections in the crystals, or to strain. Irrespective of which of these... 

Somani RH, Hsiao BS, Nogales A, Srinivas S, Tsou AH, Sics I, Balta-Calleja FJ, Ezquerra TA (2000) Structure development during shear flow-induced crystallization of i-PP in-situ small-angle X-ray scattering study. Macromolecules 33 9385-9394 Somani RH, Hsiao BS, Nogales A, Fruitwala H, Srinivas S, Tsou AH (2001) Structure development during shear flow induced crystallization of i-PP in situ wide-angle X-ray diffraction study. Macromolecules 34 5902-5909... 

Most polyphenylquinoxalines show no crystallinity in wide-angle X-ray diffraction studies. Their amorphous nature is primarily due to the configurational disorder carried out in the backbone of the polymer chains by the presence of different isomers. Glass transition temperature values decrease from 360 °C for polymer 15 to 320 °C for 16 and 290 °C for 17. However, the Tg significantly increases when the polymers are heated at... 

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