| Summary: | A number of compounds were synthesized with the ultimate goal being the synthesis of
C₂ symmetric molecules which displayed thermotropic liquid crystalline behaviour. The
compounds prepared were 4-alkoxy benzophenones, 3,4-bis-alkoxy benzophenones, 4-
alkoxy dibenzylidene acetones, 3,4-bis-alkoxy dibenzylidene acetones and 4-alkoxy-
1, 9-diphenyl-nona-l,3,6,8-tetraen-5-ones. The length of the linear alkoxy side chain was
varied from C₆H₁₃ to C₁₂H₂₅.
All compounds were characterized by FTIR, ¹H, and ¹³C NMR spectroscopy. Mesophase
behaviour of the synthesized compounds was investigated using differential scanning
calorimetry and polarizing optical microscopy.
It was determined that both the alkoxy side chain length, as well as the number of alkoxy
side chains have an effect on the ability of this class of C₂ symmetric compounds to selfassemble
into liquid crystalline phases. In addition, the overall core size and extent of
conjugation also affected mesophase formation. The mono-alkoxy benzophenones and
dibenzylidene acetones were non-mesogenic, while all four of the mono-alkoxy 1,9-
diphenyl-nona-l,3,6,8-tetraen-5-ones (alkoxy side chain of lengths C₆H₁₃, C₈H₁₇, C₁₀H₂₁
and C₁₂H₂₅)self-assembled into nematic liquid crystalline phases. Increasing the number
of alkoxy side chains from one to two per aromatic moiety helped induce liquid
crystalline formation: the corresponding bis-C₆H₁₃ benzophenone and bis-C ₆H₁₃, bis
C₈H₁₇, and bis-C₁₀H₂₁ dibenzylidene acetones were mesogenic, displaying smectic A
(benzophenone) and nematic (dibenzylidene acetone) mesophases respectively.
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