Numéro |
J. Phys. II France
Volume 4, Numéro 6, June 1994
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Page(s) | 1033 - 1048 | |
DOI | https://doi.org/10.1051/jp2:1994182 |
J. Phys. II France 4 (1994) 1033-1048
SANS study of deformation and relaxation of a comb-like liquid crystal polymer in the nematic phase
A. Brûlet1, F. Boué1, P. Keller1, P. Davidson2, C. Strazielle3 and J. P. Cotton11 Laboratoire Léon Brillouin (CEA-CNRS), CE-Saclay, 91191 Gif-sur-Yvette Cedex, France
2 Laboratoire de Physique des Solides, Bât. 510, Université Paris XI, 91405 Orsay Cedex, France
3 ICS-CRM, 6 rue Boussingault, 67083 Strasbourg, France
(Received 14 October 1993, received in final form 17 February 1994, accepted 23 February 1994)
Abstract
A comb-like liquid crystal polymer is stretched and quenched after a certain time in the nematic phase. The conformation of
the deformed chain is determined using small angle neutron scattering (SANS) as a function of the temperature of stretching,
the stretching ratio and the duration of the relaxation. The scattering data are well fitted to junction affine and phantom
network models. Some data are even well fitted by a totally affine model that we call " pseudo affine " because the only parameter,
the stretching ratio, is found to be well below the macroscopic stretching ratio. The latter result, never encountered with
amorphous polymers, is attributed to the cooperative effects of the nematic phase. We also note that the form factors of the
chain in the underformed sample remain similar in the isotropic, nematic and glassy state ; they correspond to a Gaussian
chain. The same samples were studied by wide angle X-ray scattering. On one hand, the orientation of the mesogenic groups
is found to be parallel or perpendicular to the stretching direction depending on the stretching temperature. This result
is discussed as a function of the presence of smectic fluctuations. On the other hand, longer relaxations at constant elongation
ratio do not lead to a disorganization of the mesogenic group orientation whereas the polymer chains are partly relaxed.
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