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Structure, Photochromism and Liquid Crystal Properties of 1-Alkyl-2-(Arylazo)Imidazoles (Raai-C<sub>n</sub>H<sub>2n+1</sub>, n (Even) = 10 - 22)
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作者 avijit nandi Chandana Sen +2 位作者 Debashis Mallick Randhir K. Sinha Chittaranjan Sinha 《Advances in Materials Physics and Chemistry》 2013年第2期133-145,共13页
Photochromism is the reversible structural change of the molecules upon light irradiation having different spectral pattern before and after irradiation. Liquid crystal (LC) is a long-range orientational order of the ... Photochromism is the reversible structural change of the molecules upon light irradiation having different spectral pattern before and after irradiation. Liquid crystal (LC) is a long-range orientational order of the molecules in between solid and isotropic liquid phases which share the properties of the crystal and liquid phases. 1-Alkyl-2-(ary-lazo)imidazoles, (Raai-CnH2n+1, R = H, Me and n = 10, 12, 14, 16, 18, 20, 22) exhibits photochromism and two of them (Haai-C18H37 and Haai-C22H45) show Liquid crystal (LC) properties. One of these compounds, Meaai-C16H33 is structurally characterized by single crystal X-ray diffraction study. The compounds upon irradiation with UV light show E-to-Z isomerisation. Quantum yields (φE→Z) of E-to-Z isomerisation vary with the molar mass of the compounds. The reverse transformation, Z-to-E, is recorded in thermal condition. The activation energy (Ea) of isomerisation is determined by the controlled temperature reaction. Liquid crystal property of the molecules is examined by polarizing optical microscopy (POM) and DSC. The carbon chain length n = 18 shows nematic (N)-isotropic (I) phase transition and an unknown Smectic (Sm) phase is observed with n = 22 on heating cycle. 展开更多
关键词 Arylazoimidazoles STRUCTURE PHOTOCHROMISM Liquid Crystal Nematic-Isotropic PHASE Transition SMECTIC PHASE
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