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|Title:||Studies on some smectogenic compounds with large bilayer spacings|
Urs, Subramanya Raj M.
|Publisher:||Gordon and Breach Science Publishers.|
|Citation:||Molecular Crystals and Liquid Crystals, 1983, Vol.97, p49-75|
|Abstract:||In mesomorphic compounds with strongly polar end groups, near neighbor molecules have antiparallel correlations. This results in a bilayer structure which in turn leads to several interesting phenomena like reentrance and smectic polymorphism. After a brief review of the development of this subject, we report some unusual properties in several compounds with relatively large bilayer spacings (ge 1.6 times the molecular length). For example, 4-n-decylphenyl-3'-methyl-4'-(4"-nitrobenzoyloxy)benzoate (10 PMNBB) shows a remarkably large expansion (~20%) of the bilayer spacing on cooling in the SA phase, the rate of expansion increasing with decrease of temperature. Further, the dielectric anisotropy reverses sign, becoming negative at lower temperatures. When the nitro group is replaced by a cyano group (10 PMCBB), (a) the rate of expansion of the bilayer spacing decreases with decrease of temperature, and (b) an SA - SA transition takes place with a jump of ~0.4 Å in the layer spacing at TAN - T sime 15°. We present results on several homologues of both the compounds as also on compounds with a lateral methoxy substituent.|
|Description:||Restricted Access. Paper presented at the 9th international conference on liquid crystals held at Bangalore in 1982.|
|Copyright:||1983 OPA (Overseas Publishers Association) N.V.|
|Appears in Collections:||Research Papers (SCM)|
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|1983 MCLC V97 p49.pdf|
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