Small-angle X-ray diffraction SAXD

The possibility also exists that the hard-segment domains are really crystalline, but the crystals are so small that they are not detected by WAXD. In this regard, small angle x-ray diffraction (SAXD) does detect the domains, so we know that they exist, that they have some order,... 

The above disadvantage of the lack of spatial information can be overcome by a combination of NMR data and other techniques. From the aH pulse NMR, the fraction and the molecular mobility of different molecular environment can be obtained as free induction decays (FIDs) within a short time, which is suitable for a practical, better understanding of the morphology-property relationship. Wide angle X-ray diffraction (WAXD) and small angle X-ray diffraction (SAXD) as well as electron microscopy provide direct information between the nano- and micrometre scale. A combination of NMR data with those from X-ray diffraction and electron microscopy should be able to analyse the structure from the atomic level to the macro scale. In this review, the morphology-property relationship, the dynamics of morphological transition, the kinetics of crystallisation, etc. analysed by a combination of NMR and other tools are introduced. 

LB films of five new hybrid dimethyidioctadecylammonium/heteropolyanions DODA/HPA (HPA=[PZ(H20)M0 03,], Z=Co, Cu, Mn, Zn, Ni) were prepared and characterized by it-A isotherms, UV-Vis absorption spectra, IR spectra, small-angle X-ray diffraction (SAXD), and atomic force microscope (AFM). The results show that these compounds have good film-forming property on the air-water interface. The collapse pressure of LB films is 28.7-37.5mN/m. The area per molecule is 28.18-49.07 nm mol". The LB films have lamellar structures in which the monolayers of the heteropolyanions alternate with bilayers of DODA to form centrally symmetrical LB films. 

Cholesteric mesophases in general resemble the nematic mesophase when observed by both small-angle X-ray diffraction, SAXD, and WAXD. The smectic mesophase, in contrast, produces both diffuse rings at 4--5 A and sharp rings at a distance generally, but not necessarily, equal to the repeat length of the monomer unit, between 15 and 50 A. 

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