Guinier Analysis Research Articles

X-ray structural analysis of activated silica

The structure of silica activated by different substituents/activators, Rn (Table I) was analysed by the method of radial distribution functions. The structural parameters of the space configuration of silica were determined beforehand. Fourier analysis of the angular distribution of X-ray radiation supports the existence of a tetrahedral configuration of silicon with respect to oxygen in a silica of the SiO2 + Rn type. The preliminary analysis makes grounds for further quantitative analysis, which permits the construction of a structural model of pure and activated silica with the activators built in it, and quantitative analysis of the local ordering degree in larger areas. Further specification of the structural parameters obtained by radial distribution functions [1], and of the parameters of long-range ordering obtained in the method of small-angle diffusion by Guinier analysis, are the next stage of the studies of approximation of the real structure of the analysed noncrystalline system, and are discussed in subsequent papers [1].

Small-angle neutron scattering studies of starch granule structure

Starch granules from the potato, wheat, barley, millet, waxy maize, mung bean, smooth pea and wrinkled pea have been examined as slurries in D 2O by the technique of small-angle neutron scattering (SANS). All starches except that from wrinkled peas exhibit a Bragg peak at 100 Å approximately but this disappears on gelatinization. The Bragg peak is believed to arise from alternating amorphous and crystalline regions. By the use of different D 2 O H 2 O mixtures, the isopicnic point was shown experimentally to occur at 52% D 2O w/w which was close to that calculated theoretically (50·4% D 2O w/w). Examination of native and defatted wheat starches in an isopicnic D 2 O H 2 O mixture showed evidence of a lipid peak at 152–167 Å. On the basis of this evidence and that from Debye-Scherrer broadening of the 100 Å peak it is proposed that the lipid occurs radially. Further evidence in support of these dimensions and conclusions comes from Guinier analyses of the gelatinized starch granules. Using the racemose model for amylopectin, then each raceme was found to fit optimally the SANS scattering data when it was assumed to be either a squat cylinder or ellipsoid with dimensions of 150 × 60 A ̊ .

SAXS from a poly(amido-amine)-heparin complex in aqueous solutions: a comparison between two analysis methods

Joerchel's method is applied to SAXS spectra of a poly(amido-amine)-heparin complex in aqueous “non diluted solutions”, showing a noticeable interference effect. The results are compared with those obtained by the classical Guinier analysis applied to diluted solutions of the complex.

Small‐angle X‐ray and neutron scattering studies of the morphology of ionomers

AbstractPreliminary small‐angle neutron scattering (SANS) studies have been made of different ionomers in the dry state and after saturation with water. Scattering from the dry samples arises from differences in the neutron scattering cross sections of the ionic and nonionic units in the polymer. The SANS technique is complementary to previous small‐angle x‐ray scattering (SAXS) studies since the SANS contrast differences are generally quite different than those for SAXS. A quantitative comparison is made of SANS and SAXS intensities for a dry cesium salt of an ethylene‐methacrylic acid (E‐MAA) copolymer. For water‐saturated samples the technique of isotopic replacement can be used in conjunction with SANS since saturation can be effected with either H2O or D2O. In this case information about the chemical composition of the phases is obtained from an analysis of the intensity ratio I/I. Results are consistent with the presence of a separate phase containing water molecules and ions in a matrix of the nonionic units. A Guinier analysis gives a radius of gyration of 17 Å for a water‐saturated cesium salt of an E‐MAA copolymer.