J. Phys. II France
Volume 2, Numéro 1, January 1992
Page(s) 87 - 92
DOI: 10.1051/jp2:1992115
J. Phys. II France 2 (1992) 87-92

On the spacer and mesogenic unit QNS reorientational motion investigation in liquid crystal polyacrylate

B. Cvikl and J. Peternelj

Faculty of Engineering, University of Maribor, Maribor, Slovenia, Yugoslavia and "J. Stefan" Institute, University of Ljubljana, Ljubljana, Solvenia, Yugoslovia

(Received 24 July 1991, accepted 27 September 1991)

The incoherent quasi elastic cold neutron scattering data of the side chain dynamics of the backnbone deuterated linear polymer polyacrylate of Benguigui et al. J. Phys. II France 1 (1991) 451), have been successfully interpreted in the isotropic, smectic A and re-entrant nematic phases. The spacer dynamics of the twelve protons are interpreted in terms of the mode1 according to which the protons are subjectec to the transverse oscillations of the standing wave variety with only the fundamental mode of vibrations being excited. The motion of the biphenyl group, constituting the mesogenic unit, can be appropriately described in terms of the uniaxial restricted reorientational model, according to which the benzene rings are subjected, to small step stochastic angular displacements, around their para axis, within a circular segment of an apex angle $\phi_{0}$.


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