Syntheses and Properties of Luminescent Liquid Crystals

• Main Authors: Chih-Chien Cho, 卓志鍵
• Other Authors: 余良杰
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/33001443982253207077

博士 === 淡江大學 === 化學學系博士班 === 94 === Star-shaped discogens consisted of triphenylamine and 2,4,6-trisubstituent aniline as the central core with different styryl-based side arms, and having 3 and 9 peripheral chains were synthesized. Columnar phases, uniaxially negative, were observed for compounds consisted of 9 peripheral chains (longer than 6 carbon units), but not with 3 peripheral chains. Hexagonal packing of columns was observed from the results of X-ray diffraction. However, the diameter of the column is less than the molecular dimension indicating the interdigitations of peripheral chains of the neighboring columns. Compound AN-ST-A, mixing with TNF (1/4) could induce columnar mesophase due to the intermolecular charge transfer interaction. X-shaped mesogens consisted of 1,4-di-(4-hydroxy-stryryl)-2,5-bis-(2-hydroxy-ethoxy)benzene as the central core with different side arms, and having 2, 4, 6 and 12 peripheral chains were synthesized and each of peripheral chains has 12 carbon units. The compounds having 2 and 4 peripheral chains exhibit rod-like mesophases (N, SA and SC phases) and the others exhibit disc-like mesophases. Increasing the benzoate unit in side arms did not change the mesophase behaviors but increase the clearing temperature. New merocyanine dyes were synthesized basing on 4-vinylpyridine coupling with various dihydroxybenzene by Heck reaction : 1,2-di-(N-methylpyridinium-4-ylviny)-4,5-dihydroxybenzene (I-c), 1,3-di-1,3-di-(N-methyl N-methylpyridinium-4-ylviny)-4,6-dihydroxybenzene (II-c) and 1,4-di-(N-methylpyridinium- 4-ylviny)-2,5-dihydroxybenzene ( III-c ). Solvatochromism behaviors of these dyes in various solvents were studied by UV-vis absorption and fluorescence spectroscopy. These stocky shifts resulted from the degree of solvation between dyes and solvents, including ICT (intramolecular charge transfer) from proton transfer or electron transfer. Molecule II-c exhibited the largest negative solvatochromism (Δλ = 4196 cm-1 from DMF to H2O) and can be used to be proton sensor or probe.