Issue |
Europhys. Lett.
Volume 59, Number 3, August 2002
|
|
---|---|---|
Page(s) | 364 - 369 | |
Section | Atomic and molecular physics | |
DOI | https://doi.org/10.1209/epl/i2002-00203-9 | |
Published online | 01 September 2002 |
Transient and stationary flow behaviour of side chain liquid-crystalline polymers: Evidence of a shear-induced isotropic-to-nematic phase transition
1
Laboratoire Léon Brillouin (CEA-CNRS),
CE-Saclay - 91191 Gif-sur-Yvette, France
2
Department of Physics & Astronomy and Polymer
IRC, University of Leeds Leeds LS2 9JT, UK
Received:
15
November
2001
Accepted:
30
April
2002
This letter describes the non-linear rheology of the isotropic phase of a thermotropic side chain liquid-crystal polymer (SCLCP), from which we infer a flow-induced iso- tropic-to-nematic (IN) phase transition above a critical shear stress and construct non-equilib- rium phase diagrams. In contrast to the well-studied wormlike-micellar solutions and predictions for simple liquid-crystalline systems, the critical stress does not vanish as the equilibrium transition temperature is approached from the above. We postulate that this is due to: i) the coupling between mesogens and the polymer backbone, whose equilibrium oblate nematic backbone conformation contrasts with the prolate non-equilibrium conformation; and ii) the peculiar topological constraints in SCLCP melts, which have been previously postulated as leading to long-lived clusters.
PACS: 36.20.Ey – Conformation (statistics and dynamics) / 64.70.Md – Transitions in liquid crystals / 83.50.Ax – Steady shear flows, viscometric flow
© EDP Sciences, 2002
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