Reorientation instabilities and viscoelastic measurements in a main chain thermotropic nematic polymer optical and NMR studies

P. Esnault, J. P. Casquilho, F. Volino, A. F. Martins, A. Blumstein

Research output: Contribution to journalArticle

52 Citations (Scopus)

Abstract

The reorientational behaviour of a nematic monodomain, in a static magnetic field, following the rotation of the mean director through an angle α ≈ π/2 to the magnetic field direction, is investigated by optical polarizing microscopy and proton NMR spectroscopy. Optical evidence supporting a reorientation process through a pure bend transient distortion of the director field is reported for poly (4,4′-dioxy-2,2′-dimethylazoxybenzene nonanediyl), a main-chain nematic thermotropic polymer. The time evolution of the distortion and flow patterns are deduced from a detailed analysis of the NMR lineshapes recorded during the reorientational process. The viscosity coefficients γ1, α1, α2, ηc and the ratio K3/K1 of the bend to splay Frank elastic constants are determined and discussed in terms of the existing theories.

Original languageEnglish
Pages (from-to)607-628
Number of pages22
JournalLiquid Crystals
Volume7
Issue number5
DOIs
Publication statusPublished - 1 Jan 1990

Fingerprint Dive into the research topics of 'Reorientation instabilities and viscoelastic measurements in a main chain thermotropic nematic polymer optical and NMR studies'. Together they form a unique fingerprint.

Cite this