Banana-calamitic dimers: unexpected mesophase behaviour by variation of the direction of ester linking groups in the bent-core unit

A five-ring bent-core unit and a phenyl benzoate moiety are linked together by means of a flexible spacer. Starting from dimers having different length of the aliphatic parts, that is the terminal alkyloxy chains and the spacer, the direction of each of the four ester connecting groups in the bent-c...

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Bibliographic Details
Published in:Liquid crystals 2010-06, Vol.37 (6-7), p.853-874
Main Authors: Tamba, Maria Gabriela, Baumeister, Ute, Pelzl, Gerhard, Weissflog, Wolfgang
Format: Article
Language:English
Subjects:
bent-core mesogens
Chemical compounds
Crystallography
Dimers
Electric fields
Esters
ferroelectric behaviour
Joining
liquid crystalline dimers
Materials science
Mesophase
Nematic
nematic-nematic transition
Phases
Spacers
Temperature
Thermodynamics
Transition temperature
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Summary:A five-ring bent-core unit and a phenyl benzoate moiety are linked together by means of a flexible spacer. Starting from dimers having different length of the aliphatic parts, that is the terminal alkyloxy chains and the spacer, the direction of each of the four ester connecting groups in the bent-core unit is reversed step by step. In this way thermodynamically stable polar and non-polar mesophases in unusual sequences could be obtained. For instance, a SmC s P AF -SmC s ´P AF transition and the existence of two nematic phases (N, N X ) have been observed. The nematic phases of the banana-calamitic dimers exhibit unusual properties comparable to those of the nematic phases reported for some monomeric bent-core mesogens. The electric field-induced enhancement of the SmCP-SmA transition temperature of one compound proves the existence of polar clusters already in the non-polar SmA phase.
ISSN:0267-8292
1366-5855
DOI:10.1080/02678291003798172