In this work, we validate that cellulose nanocrystals (CNCs), surface-functionalized with pro-mesogenic azobenzen pendants, can act as photoswitchable chiral solutes in a nematic liquid crystal (N-LC). Upon UV illumination, the...
Today, it is of great importance to synthesize new azo compounds as well as to conduct research in different areas of use. More than one usage area is increasing day by day in high-tech products (laser printing materials, printer toners, liquid crystals, etc.) as well as in many sectors such as paper, food, cosmetics, textile and leather. In this study, considering these advantages, the compounds of 3-amino-1H-pyrazol-5-ol, 1H-1,2,4-triazol-3-amine and 3amino-5-hydroxy-1-phenyl pyrazole were used as starting materials. As a result of azo coupling of diazonium salts with resorcinol and 3,5-dihydroxy benzoic acid, new azo compounds were synthesized, their structures were characterized by spectroscopic methods such as FT-IR and 1 H-NMR, and different solvent effects on visible absorption spectra were investigated. Molecular geometry and vibration frequency calculations of synthesized compounds were made with Density Functional Theory (DFT) using 6-311G (d,p) basis set at the B3LYP level. Additional, electronic properties and HOMO-LUMO orbital calculations were carried out with time dependent DFT (TD-DFT) approach. As a result of this study, it has been observed that azo compounds containing heterocyclic amine groups have bathochromic effects and bright colors. It is anticipated that this study will make important contributions to the literature and the dyestuff industry and will form a basis for potential applications.
In our continuing
pursuit to generate, understand, and control
the morphology of organic nanofilaments formed by molecules with a
bent molecular shape, we here report on two bent-core molecules specifically
designed to permit a phase or morphology change upon exposure to an
applied electric field or irradiation with UV light. To trigger a
response to an applied electric field, conformationally rigid chiral
(S,S)-2,3-difluorooctyloxy side
chains were introduced, and to cause a response to UV light, an azobenzene
core was incorporated into one of the arms of the rigid bent core.
The phase behavior as well as structure and morphology of the formed
phases and nanofilaments were analyzed using differential scanning
calorimetry, cross-polarized optical microscopy, circular dichroism
spectropolarimetry, scanning and transmission electron microscopy,
UV–vis spectrophotometry, as well as X-ray diffraction experiments.
Both bent-core molecules were characterized by the coexistence of
two nanoscale morphologies, specifically helical nanofilaments (HNFs)
and layered nanocylinders, prior to exposure to an external stimulus
and independent of the cooling rate from the isotropic liquid. The
application of an electric field triggers the disappearance of crystalline
nanofilaments and instead leads to the formation of a tilted smectic
liquid crystal phase for the material featuring chiral difluorinated
side chains, whereas irradiation with UV light results in the disappearance
of the nanocylinders and the sole formation of HNFs for the azobenzene-containing
material. Combined results of this experimental study reveal that
in addition to controlling the rate of cooling, applied electric fields
and UV irradiation can be used to expand the toolkit for structural
and morphological control of suitably designed bent-core molecule-based
structures at the nanoscale.
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