Shear deformation of homeotropic monodomains: Temperature dependence of stress response for flow‐aligning and tumbling nematics
作者:
Dong‐Feng Gu,
Alex M. Jamieson,
期刊:
Journal of Rheology
(AIP Available online 1994)
卷期:
Volume 38,
issue 3
页码: 555-571
ISSN:0148-6055
年代: 1994
DOI:10.1122/1.550474
出版商: The Society of Rheology
关键词: NEMATIC CRYSTALS;SHEAR FLOW;TEMPERATURE DEPENDENCE;RHEOLOGY;OSCILLATIONS;PHASE TRANSFORMATIONS;RESPONSE FUNCTIONS;VISCOELASTICITY
数据来源: AIP
摘要:
The rheological behavior of two low molar mass nematogens (LMMN), pentylcyanobiphenyl (5CB) and octylcyanobiphenyl (8CB), is studied. Over a major part of its nematic phase, 8CB shows shear stress oscillations in flow startup and step flow, characteristic of director tumbling, whereas pure 5CB has no oscillatory response but, over its entire nematic range, shows a stress overshoot, typical of flow alignment. For 8CB, the oscillation periodicity is a strong function of temperature, particularly near the SmA–N transition, and near the N–I transition where the crossover from tumbling to flow‐aligning response occurs. The transient shear response functions of each material are analyzed at different temperatures via Ericksen’s transversely isotropic fluid model to extract the Leslie viscosity coefficients α1, α2, and α3and the Miesowicz viscosity ηb. Our results are in good agreement with reported literature values.
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