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Browsing by Author "Lee, Jey-Jau"

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    Broad Ranges and Fast Responses of Single-Component Blue-Phase Liquid Crystals Containing Banana-Shaped 1,3,4-Oxadiazole Cores
    (2014-01-08)
    Chiang, I-Hung
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    Long, Chun-Ji
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    Lin, Hsin-Chieh
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    Chuang, Wei-Tsung
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    Lee, Jey-Jau
    In this study, we synthesized two novel 1,3,4-oxadiazole-based bent-core liquid crystals (OXD7*, OXD5B7F*) containing a chiral tail that display broad ranges of the blue phase III (34 and 7 K, respectively); we characterized them using polarized optical microscopy, differential scanning calorimetry, and circular dichroism. The electro-optical responses of both of these liquid crystals are much faster than those of previously reported single-component blue-phase liquid crystals. To optimize its electro-optical performance, we mixed OXD7* (the blue-phase range of which is broader than that of OXD5B7F*) with its analogue OXD6 (at weight ratios of 6:4 and 4:6). We also performed molecular modeling of single-component BPLCs (OXD7* and OXD5B7F*) to analyze the possible parameters affecting their blue phase ranges.
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    Synthesis and study of hybrid hydrogen-bonded bent-core liquid crystal complexes containing C-60- and Si-based proton donors
    (2015-01-01)
    Liu, Shih-Hsien
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    Yang, Po-Jen
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    Wei, Chong-Lun
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    Chiang, I. -Hung
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    Liao, Chun-Yen
    Novel hydrogen-bonded (H-bonded) C-60- and Si-based bent-core liquid crystal (LC) complexes containing a bent-shaped proton acceptor and C-60- and Si-based single/double armed proton donors were synthesized and mixed to produce hybrid H-bonded LC complexes. The SmCP phases could be introduced in the hybrid LC complexes with a very high C-60-based moiety up to 90 mol%. Among our H-bonded LC complexes, the hybrid LC complexes with low amounts of the C-60-based moiety (<= 24 mol%) possessed the highest spontaneous polarization value (ca. 494 nC cm(-2)), the widest mesophasic range (40.8 degrees C) and the lowest saturated electric field (8.8 V-pp mu m(-1)). Under electric fields of modified triangle waveforms, both series of hybrid H-bonded LC complexes displayed an anti-ferroelectric (AF) to a ferroelectric (FE) polar switching as the C-60-based moiety increased up to 24-50 mol%. Therefore, the hybrid H-bonded LC complexes containing a broad molar ratio (0-90 mol%) of C-60-based moiety revealed a tunable route for the electro-optical applications of C-60-based H-bonded liquid crystals.