Chiral Polymorphic Hydrazine-based Asymmetric Liquid Crystal Trimers with Resorcinol as Linking Group

Author(s): Yit-Peng Goh, Wan-Sinn Yam*, Foo-Win Yip, Gurumurthy Hegde*

Journal Name: Current Organic Synthesis

Volume 18 , Issue 4 , 2021


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Abstract:

Introduction: This is the first report on chiral polymorphic hydrazine-based asymmetric liquid crystal trimers, 1-[4'-(4''-(5-Cholesteryloxy)carbonyl)butyloxy]-3-[N-benzylideneoxy-N'-(4'''-decyloxybenzylidene) hydrazine] butyloxybenzenes, and 1-[4'-(4''-(10-cholesteryloxy)carbonyl)nonyloxy]-3-[N-benzylideneoxy-N'-(4'''- decyloxybenzylidene)hydrazine]butyloxybenzenes., in which the hydrazine and cholesterol arms were connected via two flexible methylene spacers (n = 3-12 units and m = 4 or 9, respectively) to the central resorcinol core.

Materials and Methods: FT-IR, 1D and 2D NMR spectroscopy, and CHN microanalysis were used to elucidate the structures of the trimers. Differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction were used to study the transitional and phase properties of the trimers, which were length and spacer parity dependent. Trimers with short spacer length in the cholesteryl arm, m = 4 showed an interesting phase sequence of BP/N*-TGBA*-SmA*.

Results and Discussion: The TGBA* phase was sensitive to spacer length as it was only observed in trimers with short ester linkage. For the long analogues, m = 9, characteristic visible reflection and a much simpler phase sequence with only N* and SmA* phases were observed.

Conclusion: The X-ray diffraction measurements revealed that layer periodicities of the SmA* phase were approximately half the estimated all-trans molecular length (d/L ≈ 0.44-0.52), thus suggesting that the molecules are either strongly intercalated or bent.

Keywords: Polymorphic, hydrazine, TGBA, blue phase, XRD, layer periodicity.

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Article Details

VOLUME: 18
ISSUE: 4
Year: 2021
Published on: 02 February, 2021
Page: [352 - 365]
Pages: 14
DOI: 10.2174/1570179418666210202123935
Price: $65

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