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KMID : 1059519980420060679
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Journal of the Korean Chemical Society
1998 Volume.42 No. 6 p.679 ~ p.695
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α,ω-Bis[4-(4'-(S)-(+)-2-methylbutylbiphenyl-4-carboxy)phenoxy]alkanes-Synthesis and Liquid Crystalline Properties of New Dimesogenic Compounds
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Kim Jae-Hoon
Lee Soo-Min
Jin Jung-Il
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Abstract
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A series of α,ω-bis[4-(4'-(S)-(+)-2-methylbutylbiphenyl-4-carboxy)phenoxy]alkanes were synthesized, and their thermal and liquid crystalline properties were studied. The chain length of the central polymethylene spacers, x, of the chiral twin compounds was varied from 3 to 12. These compounds were characterized by elemental analysis, IR and NMR spectroscopy, differential then-nal analysis (DSC), and crosspolarized microscopy. All compounds were found to be enantiotropic liquid crystalline, and the values of melting (Tm) and isotropization temperature (Ti) as well as ΔHi and ΔSi decreased in a zig-zag fashion, revealing the socalled odd-even effect as x increased. Their mesomorphic properties fell into four categories depending upon x; (a) compounds with x=3, 4 and 5 formed only a cholesteric phase on heating, while on cooling they went through two transitions of isotropic (I)-to-cholesteric (Ch) and Ch-to-smectic A (SA) phases before crystallization. (b) compounds with x=6, 8 and 10 exhibited only a cholesteric phase both on heating and on cooling. (c) compounds with x=7 and 9 went through three transitions of crystal (C)-to-SA, SA-to-Ch, and Ch-to-I phases on heating while on cooling they went through four transitions of 1-to-Ch, Ch-to-SA, SA-to-Smectic C (Sc), and SC-to-C phases in that order, and (d) compounds with x=11 and 12 went reversibly through four transitions of C-to-SC, SC-to-SA, SA-to-Ch, and Ch-to-I phases.
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