Banti Baishya , Amit Kumar Pradhan , Abhijit Paul , Arghyadeep Bhattacharyya , Homen Dahal , Mrinmoy Roy , Achalkumar Ammathnadu Sudhakar , Manoj Kumar Paul
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New azo-functionalized symmetrical liquid crystal dimers: Synthesis, photophysical studies, mesomorphism and DFT studies
New azo-functionalized symmetrical liquid crystal dimers linked by flexible methylene ether spacers were synthesized. The achiral four-ring rod-shaped monomer comprises a 4-n-nonyloxy terminal chain containing imine, ester, and photochromic azo groups as linking moieties. The lateral methyl group is introduced in the monomeric units to reduce the phase transition temperature. Thermogravimetric analysis was employed to assess the thermal stability of the azo-functionalized dimers. The thermal stability of the dimers increased with increasing spacer lengths. Azo functionalized dimers display a wide range of enantiotropic nematic phases. The azo-functionalized dimers (BDAN-n) were fluorescent with large Stokes shift. The bi-exponential model successfully fitted the emission lifetime decays, yielding two lifetime components τ1 = 0.8–1.0 ns and τ2 = 1.5–2.3 ns. The photoisomerization of the azo-functionalized dimers under ultraviolet irradiation showed a conversion efficiency that diminished as the alkylene spacer length increased. Computational studies confirmed the stable geometries and chemical reactivity of the dimers.
期刊介绍：
Dyes and Pigments covers the scientific and technical aspects of the chemistry and physics of dyes, pigments and their intermediates. Emphasis is placed on the properties of the colouring matters themselves rather than on their applications or the system in which they may be applied.
Thus the journal accepts research and review papers on the synthesis of dyes, pigments and intermediates, their physical or chemical properties, e.g. spectroscopic, surface, solution or solid state characteristics, the physical aspects of their preparation, e.g. precipitation, nucleation and growth, crystal formation, liquid crystalline characteristics, their photochemical, ecological or biological properties and the relationship between colour and chemical constitution. However, papers are considered which deal with the more fundamental aspects of colourant application and of the interactions of colourants with substrates or media.
The journal will interest a wide variety of workers in a range of disciplines whose work involves dyes, pigments and their intermediates, and provides a platform for investigators with common interests but diverse fields of activity such as cosmetics, reprographics, dye and pigment synthesis, medical research, polymers, etc.
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