Subject small-angle

This state of partial deformation has been determined recently by small angle neutron scattering [194] and has been a favorite subject of investigation in the... 

The conformation of polymer chains in an ultra-thin film has been an attractive subject in the field of polymer physics. The chain conformation has been extensively discussed theoretically and experimentally [6-11] however, the experimental technique to study an ultra-thin film is limited because it is difficult to obtain a signal from a specimen due to the low sample volume. The conformation of polymer chains in an ultra-thin film has been examined by small angle neutron scattering (SANS), and contradictory results have been reported. With decreasing film thickness, the radius of gyration, Rg, parallel to the film plane increases when the thickness is less than the unperturbed chain dimension in the bulk state [12-14]. On the other hand, Jones et al. reported that a polystyrene chain in an ultra-thin film takes a Gaussian conformation with a similar in-plane Rg to that in the bulk state [15, 16]. 

X-ray scattering from coal was the subject of several early studies which led to the postulation that coal contains aromatic layers about 20 to 30 A in diameter, aligned parallel to near-neighbors at distances of about 3.5 A (Hirsch, 1954). Small-angle x-ray scattering, which permits characterization of the open and closed porosity of coal, has shown a wide size distribution and the radius of gyration appears to be insufficient to describe the pore size. Application of the Fourier transform technique indicated that some coals have a mesoporosity with a mean radius of 80 to 100 A (Guet, 1990). 

As explained in Sec. 7.1, epoxy networks have been and are still the subject of controversy. This is mainly based on the particular interpretation of results obtained using microscopy techniques. On the contrary, results obtained with small-angle neutron scattering (SANS) proved that typical diepoxy-diamine networks were homogeneous (Wu and Bauer, 1985). 

Distinct butterfly patterns have also been observed when inhomogeneous gels are deformed by uniaxial deformation. The length scales in such systems, however, are usually much smaller that those encountered for polymer solutions subject to flow, and small-angle... 

Small-angle light scattering has also been extensively applied to PLCs subject to flow [173]. As in the case of scattering dichroism, SALS patterns arise principally from fluctuations in orientation, and these arc strongest in the vicinity of disclinations, or defects in the director field. The experimental geometries used for SALS in liquid crystals normally use polarizers placed before and after the sample. The arrangements include VV scatter-... 

Produced by the EW technique CNM were subjected to investigation using XRD analysis, electron microscopy, and mass-spectrometer analysis. The typical XRD patterns for the exploded materials in different conditions are shown in Fig. 1 and Fig. 2. It is immediately obvious that there is a presence of additional diffraction peaks at small angle values besides those typical for common graphite. This fact clearly demonstrates the appearance of new structural compositions in the synthesis products. A phase analysis performed shows that these diffraction peaks correspond to those for carbonic spatial materials with the fullerene-like structure of the C60-C70 types. 

The most common dynamic method is oscillatory testing, in which the sample is subjected to a sinusoidal oscillatory strain, and the resulting oscillatory stress measured. The more sophisticated rotational viscometers have the additional capability of dynamically testing liquid-like materials using small angle oscillatory shear. A parallel disc viscometer can be set up for testing solid-like materials (e.g., butter), in oscillatory shear. Some UTM-type solids rheometers, in which the moving crosshead can be made to reciprocate sinusoidally, can be used to test solid-like materials in oscillatory deformation in compression, tension or shear. 

Fig. 1.17 Small-angle neutron scattering pattern for a sample of per-deuterated lightly branched polyethylene containing 10% of hydrogen containing linear polyethylene. The sample is molten and has just been subjected to deformation in a channel die. The flow axis is horizontal and the effective extension ratio is 3.

Most of the research effort on the ionomers has been devoted to only a small number of materials, notably the ethylenes the styrenes, the rubbers(9)5 and those based on poly(tetra-fluoroethylene), the last of which is the subject of the present volume. As a result of these extensive investigations, it has become clear that the reason for the dramatic effects which are obsverved on ion incorporation is, not unexpectedly, the aggregation of ionic groups in media of low dielectric constant. Small angle X-ray and neutron scattering, backed up by a wide range of other techniques, have demonstrated clearly the existence of ionic... 

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