Estimation of parameters of the scattering particles in elastoidin by low-angle X-ray methods

Low-angle x-ray scattering methods have been used to evaluate some parameters like specific inner surface of the dispersed phase, transverse lengths, the length of in homogeneity, the length of coherence, and the air-fraction of the scattering particles in Elastoidin. The low-angle Kratky camera of the latest design was used for the experimental measurements. Since the sample under investigation is a densely packed solid polymer, the theories of Kratky and Kratky and Porod have been used to evaluate these parameters.     

Estimation of the molecular weight and other parameters of macromolecules in jute by low-angle X-ray methods

Summary Low-angle X-ray scattering methods have been applied to determine the molecular volume and the molecular weight of the macromolecules present in jute fibres. The well-known low-angle scattering camera ofKratky (1) was used and the angular range investigated is from 0.17×10^–3 to 3.0×10^–3 radians. The evaluation of the parameters and the quantities were made after the theories ofGuinier (2),Kratky (3), andPorod (4).The particles in jute fibres may be of the lamella type as pointed out byKratky (30) and also recently byRoy andDas (33). The molecular volume of the macromolecules is found out to be 9.995 × 10⁶ ų . The molecular weight is 7.703×10⁶.With 5 figures and 1 table     

A small-angle X-ray scattering study of bromine-containing latex particles

A small-angle X-ray scattering (SAXS) study of two-stage latices (TSL), composed of polystyrene (PS) and polytribromostyrene (PTBrS), is presented. The analysis of the scattering curves leads to the conclusion that the TSL particles have a concentric core-shell structure. When a PTBrS latex was used as a seed, its particles were overcoated with a PS shell during the second-stage polymerization. However, only a small portion of the seed particles were overcoated with a PTBrS shell when using a PS seed. The size distributions of the TSL and the PTBrS latex particles were determined from the scattering curves, using the method of Indirect Fourier Transformation. The resulting average radii were in good agreement with the values obtained from TEM observations. © 1996 John Wiley & Sons, Inc.     

Considerations in the determination of orientational order parameters from X-ray scattering experiments

An assessment of the data processing and analysis methods used to obtain the second- and fourth-rank orientational order parameters of liquid crystals from X-ray scattering experiments has been carried out, using experimental data from four extensively studied alkyl-cyanobiphenyls and calculated data generated from two general types of theoretical orientational distribution function. The application of a background subtraction and two different baseline correction methods to the scattering profiles is assessed, along with three different methods to analyse the processed data. The choice of baseline correction method is shown to have a significant effect: an offset to zero overestimates the order parameters from the experimental and calculated data sets, particularly for lower order parameters arising from broad distributions, whereas an offset to a value estimated from regions of low scattering intensity provides experimental values close to those reported from other experimental techniques. By contrast, the three different analysis methods are shown generally to result in relatively small absolute differences between the order parameters. We outline a straightforward general approach to experimental X-ray scattering data processing and analysis for uniaxial phases that results in order parameters that match well with those reported using other experimental techniques.     

Low-angle x-ray estimation of macromolecular parameters of the scattering particles in Agave sisalana

Various macromolecular parameters of Agave sisalana (sisal) fiber were investigated by the low-angle x-ray scattering method. The well known Kratky camera of the latest design was utilized for the experimental measurements. The sample studied was a densely packed colloidal system belonging to a general micelle system, and the theories of Kratky and Kratky and Porod were utilized to estimate the parameters. Pore analysis of the substance yields a value for the specific inner surface of the dispersed phase of 0.406 × 10^?1 m²/cm³; the transversal length is the same as the length of inhomogeneity, 107.31 Å, and the length of coherence is 342.21 Å. The air fraction of the scattering particles was found to be 0.01%.     

Investigation of the adsorption of surfactants on the poly(styrene) latex particles by small-angle X-ray scattering

We present the study of the adsorption of a non-ionic surfactant onto latex particles by small-angle X-ray scattering (SAXS). The analysis of the process of adsorption by SAXS is discussed in detail. It is demonstrated that SAXS allows to monitor the gradual built-up of the surface layer with increasing amount of added surfactant. SAXS also allows to obtain the radial volume fraction of the hydrophilic tails of the surfactant. Possible limitations of this analysis are discussed.     

Gel-permeation chromatography: X. Molecular weight detection by low-angle laser light scattering

Effluent from a gel-permeation chromatographic column has been simultaneously and continuously monitored with a differential refractometer and a low-angle laser light-scattering (LALLS) photometer. This provides a true and direct determination of molecular weight distribution rather than through a calibration method as obtained by conventional GPC techniques. Computer assisted data reduction provides a rapid determination of M?_w, M?_n, M?_z, M?_w/M?_n, as well as a plot of molecular weight distribution. Samples of very narrow molecular weight distribution (MWD) polystyrene from Pressure Chemicals Co. and relatively wide MWD samples of poly(methyl methacrylate) in chloroform have been characterized.     

Determination of static microstructure of dilute and concentrated suspensions of anisotropic particles by ultra-small-angle X-ray scattering

Ultra-small-angle X-ray scattering was performed on suspensions of anisotropic polystyrene particles of varying degrees of anisotropy. The wave vector dependence of particle form factors is well described by a model developed by Debye for the scattering from fused spheres. As volume fraction is raised, all suspensions undergo a disorder/order phase transition. The scattering from disordered and ordered suspensions of anisotropic particles is the same as that of spheres up to volume fractions of 0.45, suggesting that, in the dilute crystalline phase, the anisotropic particles order into a rotator or plastic crystal phase, where the particle centers of mass are ordered, but the particle directors are randomly distributed. Further increase in particle volume fraction leads to differences in scattering between homonuclear dicolloids and spheres, implying that the homonuclear dicolloids form a body-centered tetragonal phase with both positional and directional order. This conclusion is supported by real-space imaging of dried films of the particles.     

Morphology of dry lignins and size and shape of dissolved kraft lignin particles by X-ray scattering

Lignin is a highly branched polymer consisting of phenylpropane units, and it is one of the ingredients of the supporting matrix in plant cell walls. The morphology of several lignins extracted from plant cell walls using different methods was studied by small-angle and ultra-small-angle X-ray scattering. A power-law type intensity was observed for the dry lignins, but on the basis of the power-law exponent the fractal approach often applied to lignins is not fully justified. However, the intensity of kraft lignin did show a power law with surface fractal dimension D(s) = 2.7 +/- 0.1. The specific surface area of the lignins ranged from about 0.5 to 60 m(2)/g with 20% relative accuracy. The radius of gyration was determined from small-angle X-ray scattering data for aqueous solutions of kraft lignin. The shape of the particles in NaCl and NaOH solutions was found to be elongated. The particles were about 1-3 nm thick, while the length (5-9 nm) depended on the solvent and on the lignin concentration. The size of these primary particles was approximately the same as the size of the pores in the fractal aggregates of the dry kraft lignin. Their size was determined to be about 3.5 nm.     

Light scattering by cubic particles in the Rayleigh-Gans region

Summary The light scattered by cubic particles in theRayleigh-Gans domain is considered and an expression is derived for the particle scattering factor of a dispersion of randomly oriented cubes. Numerical results are presented for the dissymmetry as a function of the side length of the cube and the wavelength of the incident radiation. The total scattering cross section is also considered.

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Zusammenfassung Das von kubischen Teilchen imRayleigh-Gans-Bereich gestreute Licht wird untersucht und ein Ausdruck für den Teilchen-Streufaktor einer statistisch orientierten Verteilung von Würfeln abgeleitet. Die numerischen Ergebnisse für die Dissymmetrie sind dargestellt als Funktion der ScitenlÄnge des Würfels und der WellenlÄnge der einfallenden Strahlung. Der totale Streuquerschnitt wird ebenfalls angegeben.

     

Light scattering by polyhedral particles in the Rayleigh-Gans domain

Summary The light scattering properties of certain regular polyhedral particles in theRayleigh-Gans region are considered. The particle scattering factors are derived for dispersions of square pyramids and dispersions of octahedra, oriented at random to the incident beam. Numerical results are presented both for the average scattering factor and for the average 45° dissymmetry of arrays of such particles.

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Zusammenfassung Es wurde die Lichtstreuung pyramidenf?rmiger und oktaedrischer Teilchen imRayleigh-Gans-Bereich untersucht und Ausdrücke für den Teilchen-Streufaktor bei statistischer Orientierung solcher Teilchen abgeleitet. Für den mittleren Teilchen-Streufaktor und für die mittlere Dissymmetrie wurden numerische Ergebnisse angegeben.

     

X-ray scattering by black foam films

The x-ray scattering by the three types of black foam films (common black, Newton black, and stratified black films) was experimentally studied. A special device in which flat black films with an area of ca. 2 cm² can be produced was developed and x-ray diffraction patterns were obtained by a vertical diffractometer. The three types of films differ significantly in their x-ray reflections, which proves that they have different structure. For common black films, the comparison of observed and calculated intensities lead to a model, which corresponds to the three-layer model. The Newton black films exhibit diffraction trace with only one highly asymetric peak and there is, as of yet, no unambigous interpretation. The patterns of the stratified black films have several pronounced sharp peaks corresponding to the areas of different films with a given thickness.     

Incoherent X-ray scattering by K-shell electrons

Values of the incoherent scattering function S_K for scattering of photons from K-shell electrons are computed for ₂He, ₃Li, ₄Be and ₅B at photon energies 6, 10, 14, and 18 keV by using screened hydrogenic wavefunctions. The screening has been taken into account by the Thomas-Fermi model of the neutral atom. Unlike the previous calculations we have used a distorted Coulomb wavefunction for the ejected electron. The effects of Coulomb distortion and of screening corrections are discussed. It is shown that the screening correction and the Coulomb distortion in the ejected electron wavefunction play significant roles in the study of incoherent X-ray scattering by bound electrons.     

Estimation of morphological characteristics of single particles from light scattering data in flow cytometry

Numerical methods for solving the reverse problem of light scattering for single particles and a variety of experimental results have been reviewed. In particular, the two-dimensional Mie scattering method for the estimation of sizes and refractive indices of single particles has been developed. The method of triple two-dimensional Mie scattering has been elaborated, which extends the range of particle sizes with correct solutions of the reverse light scattering problem. The flying light scattering indicatrix method, which allows the estimation of the parameters of spherical particles, is presented. The results of the use of a flow cytometer of standard design for the anaysis of milk microflora and for an AIDS immunoassay by latex agglutination are given. The design of a scanning flow cytometer is considered. The results of measuring the light scattering from polystyrene latex particles are given.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1181–1190, July, 1994.The author is grateful to A. K. Petrov and M. A. Kamkhe for supporting the work on cytometry, E. G. Saprykin for useful discussion and comments, G. Alm (Swedish Agricultural Univ.) for initiating the interest to immunological studies, and A. V. Chernyshev, T. S. Mashnin, V. I. Prots, and A. A. Doroshkin for cooperation.     

The effect of annealing on the dielectric properties of horn keratin in theβ form

Summary The dielectric properties of horn keratin which has had its crystalline portions converted from the helical form to the random form have been examined and various relaxation processes were studied.The method of transforming from the a to the random form introduced internal stresses and the effect of these stresses on the relaxation processes was studied by relieving the stresses with a temperature cycling procedure which annealed the random keratin.It was found that the annealing increased markedly the relaxation time of the relaxation process associated with main chains in the amorphous regions. The d. c. conductance also was reduced by annealing. The dielectric properties of the annealed random keratin were so similar to those of keratin that it is highly probable that the dielectric properties are those of the amorphous material.

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Zusammenfassung Die dielektrischen Eigenschaften von Hornkeratin, dessen kristalline Anteile aus der-Helix-Form in die statistische-Form umgewandelt wurden, sind vermessen worden. Die Umwandlung von der- in die-Form läßt Verspannungen im Material entstehen. Die Auswirkung dieser Verspannungen auf das Relaxationsverhalten läßt sich näher studieren, wenn man das umgewandelte Horn-Material mit verschiedenen Temperatur-Zeitprogrammen behandelt, tempert und nach solchen Behandlungen die Auswirkung auf das Relaxationsverhalten prüft.Es zeigt sich, daß die Temperung die Relaxationszeit, die mit der Hauptkettenbeweglichkeit in den amorphen Bereichen verknüpft ist, merkbar erhöht. Die Gleichstrom-Leitfähigkeit wird durch die Temperung ebenfalls beeinflußt, vermindert.Die dielektrischen Eigenschaften des getemperten-Keratins sind dem von-Keratin so ähnlich, daß wir es als höchstwahrscheinlich betrachten, daß die dielektrischen Eigenschaften die des amorphen Materials darstellen.

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With 6 figures and 2 tables     

Physical gels from PVC: molecular structure of pregels and gels by low-angle neutron scattering

In this paper we report on investigations into the short-range molecular structure of pregels (aggregates formed in dilute solutions) and gels as a function of ageing time, temperature and solvent type. In some solvents (diethyl oxalate and bromobenzene) it is found that the structure of the pregels is cylinder-like or ellipsoid-like. The structure is seen to be the same for the gels and the pregels in the investigated range of transfer momentum which leads us to conclude that the gels are probably fiber-like, a statement in agreement with the morphology observed by Yang and Geil. The fiber section is also about the same order of magnitude as that reported by these authors. Also, further evidence is given for the existence of a second type of physical knot, different from those formed by the more syndiotactic sequences. The validity of the molecular structures deduced from these experiments is discussed in the light of macroscopic properties such as compression modulus and swelling.