Supramolecular self-assembly of a novel hydrogen-bonded cholesteric liquid crystal exhibiting macromolecular behaviour |
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| Authors: | Mahdi Roohnikan Seyed Reza Ghaffarian Nobuyuki Tamaoki |
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| Institution: | 1. Faculty of Polymer Engineering and Color Technology , Amirkabir University of Technology , Tehran , Iran;2. National Institute of Advanced Industrial Science and Technology , Tsukuba , Japan;3. Research Institute for Electronic Science , Hokkaido University , Sapporo , Japan |
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| Abstract: | The mesomorphic, thermoptic and glass-forming properties of 4-6-((cholesteryloxy) carbonyl)oxy hexyloxy] benzoic acid (Ch-BA) have been investigated as a novel supramolecular hydrogen-bonded cholesteric mesogen. Fourier transform infrared and 1H nuclear magnetic resonance studies have confirmed the chemical structure and the hydrogen-bond formation between the mesogens. According to polarising optical microscope observations, the compound exhibited smectic and chiral nematic phases. Differential scanning calorimetry indicated an unexpected glass transition (T g) around 32°C and a liquid crystalline region between 32 and 122°C, in which the cholesteric phase appeared at 80°C. As a result of the glass formation, samples of Ch-BA which were rapidly cooled below the T g were found to preserve the long-range ordering of the liquid crystalline state and retained the iridescent colours of the cholesteric phase. These results led to the conclusion that the formation of identical dimers by intermolecular hydrogen-bonding of the terminal carboxylic acids accompanying the lateral packing of the rigid cores, built a trimeric arrangement and this was responsible for the macromolecular behaviour of Ch-BA, despite its relatively simple structure and low molecular weight. |
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| Keywords: | Macromolecular behaviour cholesteric liquid crystal hydrogen-bonding supramolecular self-assembly |
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