Tolane oligomers: Model thermotropic liquid crystals
作者:
RobertJ. Twieg,
Vano Chu,
Cattien Nguyen,
ChristineM. Dannels,
Christopher Viney,
期刊:
Liquid Crystals
(Taylor Available online 1996)
卷期:
Volume 20,
issue 3
页码: 287-292
ISSN:0267-8292
年代: 1996
DOI:10.1080/02678299608032037
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
The liquid crystalline phases of several rigid-rod, non-polar tolane oligomers are characterized by differential scanning calorimetry and transmitted polarized light microscopy. We determine that a stable nematic phase can be formed at ambient pressure if the molecular axial ratio (length-to-width ratio) is greater than 4.5. A smectic phase forms in addition to the nematic phase if the axial ratio exceeds 6.1. Symmetrical fluorination of the terminal phenyl groups reveals that the liquid crystalline phase behaviour of these rigid rods is highly sensitive to perturbations of the charge distribution along the molecules. Nematic tolane oligomers can exhibit high stregth disclinations (s= ±3/2 and ±2) in their schlieren textures, and we discuss conditions that promote the stability of these defects.
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