Neutron scattering studies of molecular conformations in liquid crystal polymers |
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Authors: | L Noirez F Moussa J P Cotton P Keller G Pépy |
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Institution: | (1) Laboratoire Léon Brillouin (CEA-CNRS), CEN-Saclay, 91191 Gif-sur-Yvette Cedex, France |
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Abstract: | A comblike liquid crystal polymer (LPC) is a polymer on which mesogenic molecules have been grafted. It exhibits a succession of liquid crystal phases. Usually the equilibrium conformation of an ordinary polymeric chain corresponds to a maximum entropy, i.e., to an isotropic spherical coil. How does the backbone of a LCP behave in the nematic and smectic field? Small-angle neutron scattering may answer this question. Such measurements are presented here on four different polymers as a function of temperature. An anisotropy of the backbone conformation is found in all these studied compounds, much more pronounced in the smectic phase than in the nematic phase: the backbone spreads more or less perpendicularly to its hanging cores. A comparison with existing theories and a discussion of these results is outlined. |
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Keywords: | Conformations of polymers small-angle neutron scattering liquid crystal structures polymers transitions of liquid crystals |
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