| Autor: |
Davidson, P., Pansu, B., Levelut, A. M., Strzelecki, L., Davidson, P., Pansu, B., Levelut, A. M., Strzelecki, L. |
| Zdroj: |
Journal de Physique II; January 1991, Vol. 1 Issue: 1 p61-74, 14p |
| Abstrakt: |
The X-ray diffraction patterns of mesomorphic side chain polymers in the SAphase present diffuse streaks in shape of “butterfly wings”. We show that this diffuse scattering may be due to the presence of edge dislocations. On the basis of a previous description of edge dislocations within the framework of the elastic continuum theory of the SAphase given by De Gennes, we have calculated the Fourier transform of the deformation field. Optical diffraction experiments on sketches of defects have also been made to reproduce the X-ray scattering patterns. Both methods show that this diffuse scattering may indeed be due to the presence of edge dislocations. Their density may be roughly estimated to some 108/cm2. The size of their cores should be only a few Ångströms. From the decay of their elastic deformation field, a typical length λ= (K/B)1/2≈1,5 Å can be obtained which shows that the elastic constant Bof compression of the layers should be about two orders of magnitude larger in the “polymeric” SAphase than in the “conventional” one. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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