Local Aspects of Non-Elastic Deformation in Atactic Glassy Polystyrene

1986 ◽  
Vol 79 ◽  
Author(s):  
G. Coulon ◽  
J. M. Lefebvre ◽  
M. Rawiso
Keyword(s):  
Elastic Deformation ◽  
Monomer Unit ◽  
Shear Banding ◽  
Variation Method ◽  
Isotopic Labelling ◽  
Contrast Variation ◽  
Phenyl Rings ◽  
Thin Thread ◽  
Chemical Resolution ◽  
Different Parts

AbstractAtactic glassy polystyrene has been deformed by shear banding. The influence of the macroscopic shear stress down to a scale smaller than the dimensions of the macromolecules has been investigated by small-angle neutron scattering. The chemical resolution has been improved by using isotopic labelling on different parts of the monomer unit. The analysis of the experimental scattering curves has been made according to the thin thread model with a superimposed thickness. On the other hand, the contrast variation method has been applied in order to determine both the structure factor of the phenyl rings and that of the backbone part of the chain. This allows us to precise the influence of non-elastic deformation on the local structure of the chain.

Neutron diffraction, inelastic scattering and the structure of amphiphiles and macromolecules in solution

1975 ◽  
Vol 345 (1640) ◽  
pp. 119-144 ◽  
Keyword(s):  
Neutron Diffraction ◽  
Inelastic Scattering ◽  
Cross Sections ◽  
Biological Molecules ◽  
Variation Method ◽  
Contrast Variation ◽  
Structure And Dynamics ◽  
Spin Resonance ◽  
Scattering Lengths ◽  
Scattering Cross Sections

The methods by which neutron diffraction and inelastic scattering may be used to study the structure and dynamics of solutions are reviewed, with particular reference to solutions of amphiphile and biological molecules in water. Neutron methods have particular power because the scattering lengths for protons and deuterons are of opposite sign, and hence there exists the possibility of obtaining variable contrast between the scattering of the aqueous medium and the molecules in it. In addition, the contrast variation method is also applicable to inelastic scattering studies whereby the dynamics of one component of the solution can be preferentially studied due to large and variable differences in the scattering cross sections. Both applications of contrast variation are illustrated with examples of amphiphile-water lamellar mesophases, diffraction from collagen, viruses, and polymer solutions. Inelastic scattering observations and the dynamics of water between the lamellar sheets allow microscopic measurements of the water diffusion along and perpendicular to the layers. The information obtained is complementary to that from nuclear magnetic resonance and electron spin resonance studies of diffusion.

scholarly journals Small-angle scattering from multiphase fractals

2014 ◽  
Vol 47 (1) ◽  
pp. 198-206 ◽  
Author(s):  
A. Yu. Cherny ◽  
E. M. Anitas ◽  
V. A. Osipov ◽  
A. I. Kuklin
Keyword(s):  
Power Law ◽  
Small Angle ◽  
Small Angle Scattering ◽  
Variation Method ◽  
Multiphase System ◽  
Model Parameters ◽  
Contrast Variation ◽  
Crossover Point ◽  
Two Phase ◽  
Angle Scattering

Small-angle scattering (SAS) intensities observed experimentally are often characterized by the presence of successive power-law regimes with various scattering exponents whose values vary from −4 to −1. This usually indicates multiple fractal structures of the sample characterized by different size scales. The existing models explaining the crossover positions (that is, the points where the power-law scattering exponent changes) involve only one contrast parameter, which depends solely on the ratio of the fractal sizes. Here, a model that describes SAS from a multiphase system with a few contrast parameters is described, and it is shown that the crossover position depends on the scattering length density of each phase. The Stuhrmann contrast variation method is generalized and applied to experimental curves in the vicinity of the crossover point beyond the Guinier region. The contrast variation is applied not to the intensity itself but to the model parameters, which can be found by fitting the experimental data with the suggested interpolation formula. The model supplements the existing two-phase models and gives the simple condition of their inapplicability: if the crossover point depends on the contrast then a two-phase model is not relevant. The developed analysis allows one to answer the qualitative question of whether one fractal `absorbs' another one or they are both immersed in a surrounding homogeneous medium like a solvent or solid matrix. The models can be applied to experimental SAS data where the absolute value of the scattering exponent of the first power-law regime is higher than that of the subsequent second power-law regime, that is, the scattering curve is `convex' near the crossover point. As is shown, the crossover position can be very sensitive to contrast variation, which influences significantly the length of the fractal range.

scholarly journals Neutron diffraction measurements of live frog muscle using the contrast variation method

1999 ◽  
Vol 39 (supplement) ◽  
pp. S189
Author(s):  
S. Fujiwara ◽  
Y. Takezawa ◽  
Y. Sugimoto ◽  
K. Wakabayashi
Keyword(s):  
Neutron Diffraction ◽  
Frog Muscle ◽  
Variation Method ◽  
Contrast Variation
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