VISCOSITY MEASUREMENTS IN THE NEMATIC AND SMECTIC A PHASES OF A LIQUID CRYSTAL CRITICAL BEHAVIOUR

L. Léger , A. Martinet

Measurements in a rectangular channel of the three viscosities η1, η3, η2 for laminar flow with the director parallel or perpendicular to the velocity or homeotropic orientation respectively, are reported for 4-n-octyloxy-4-cyanobiphenyl. In the nematic range, η1 has a pronounced divergence near the nematic/smectic transition temperature TNA compatible with a critical exponent ν= 0.36 ± 0.05, over three decades of temperature, while η2 and η3 remain regular. The twist viscosity γ1 and the surface tension have also been measured. The divergence of γ1 is compatible with that of η1. In the smectic range, a permeation regime is observed when the flow is normal to the smectic layers leading to a very large anisotropy of the viscosities (η1/η2 ≈ 150 for ƊT ≈ 3 x 10-1 °C).

Domaines: Articles anciens

L. Léger, A. Martinet. VISCOSITY MEASUREMENTS IN THE NEMATIC AND SMECTIC A PHASES OF A LIQUID CRYSTAL CRITICAL BEHAVIOUR. Journal de Physique Colloques, 1976, 37 (C3), pp.C3-89-C3-97. ⟨10.1051/jphyscol:1976316⟩. ⟨jpa-00216499⟩