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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 21, Number 1
BKCSDE 21(1)
January 20, 2000 

 
Title
Dimesogenic Compounds with Chiral Tails: Synthesis and Liquid Crystalline Properties of a Homologous Series of a aa a, w ww w-Bis[4-(4'-(S)-( - )-2-methylbutoxycarbonyl-biphenyl-4-oxycarbonyl)phenoxy]alkanes
Author
E-Joon Choi, * Bong-Ku Choi, Jae-Hoon Kim, Jung-Il Jin
Keywords
Abstract
A series of new liquid crystalline dimesogenic compounds with chiral tails was synthesized, and their thermal and liquid crystalline properties were studied. The chain length of the central polymethylene spacers (x) was varied from dimethylene (2) to decamethylene (12). These compounds were characterized by elemental analysis, IR and NMR spectroscopy, differential scanning calorimetry (DSC), and cross-polarizing microscopy. All compounds were found to be enantiotropically liquid crystalline, and the values of melting (Tm) and isotropiza-tion temperature (Ti) as well as enthalpy change (ΔHi) and entropy change for isotropization (ΔSi) decreased in a zig-zag fashion revealing the so-called odd-even effect as x increases. Their mesomorphic properties fall into three categories depending upon x; (a) compounds with x=2 and 4 formed two different mesophases, smectic and cholesteric phases in that order on heating, and vice versa on cooling, (b) compounds with x=3, 7, 8, 10 and 11 reversibly formed only the cholesteric phase, and (c) compounds with x=5, 6, 9 and 12 exhibited only a cholesteric phase on heating, whereas on cooling they formed two different mesophases, cholesteric and smectic phases, sequentially.
Page
110 - 117
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