The trans-cis-trans isomerization process for a series of azobenzene hybrid materials has been studied by UV-Vis spectroscopy. The photoisomerization process is mainly independent of the position and chemical nature of the substituents. The kinetics of the thermal back reaction for the azo-hybrids depend strongly on the chemical nature of the substituent and substitution pattern, with thermal relaxation rate constant ranging from 3.29×10-5 to 6.49×10-2 s-1. The photoresponsive properties can be tune up by changing substituent nature and position on the azo-chromophore. These photoresponsive hybrid materials are optimal molecules for storage data applications and for designing fast optical switching devices.
In this paper, a detailed optical characterization of a series of 4-nitro/cyan, 2-nitro/cyan and 2,4-nitro/cyan substituted azobenzenes is carried out. The first-order hyperpolarizabilities of organic chromophores were determined by solvatochromic method. Different nonlinear optical behaviour is evidenced when the ortho position of an azo molecule is
occupied by acceptor and donor substituents. An increase of first-order hyperpolarizability was noticed in the case of 2,4-disubstituted azobenzenes as compared to the monosubstituted ones. Solvent effect on the UV-Vis absorption spectra
of azo-polymers was investigated using Kamlet-Taft multiparameter equation. Kamlet-Taft equation revealed that
hydrogen bond acceptor properties and dipolarity/polarizability of the solvent have a significant contribution upon the solvatochromic behavior of azo-derivatives.
In this paper we report a series of side-chain polymers bearing a push-pull azo-moiety, from pseudo-stylbene type
molecules. The azobenzene monomer is chemically incorporated through radical copolymerization in: poly(methacrylate), poly(styrene); and poly(oxazoline) matrices. The different classes of azo-polymers are discussed comparatively to one another from the point of view of: solubility, molecular weights, glass transition temperatures and thermal stability, chromophore contents, and as well as from the point of view of their spectral features.
In this paper we present a series of side-chain polymers bearing original azo-moieties, namely:
poly(methacrylate)s and poly(maleimide-styrene)s; designed for nonlinear optics (NLO). The different classes of azopolymers
are discussed comparatively to one another from the point of view of: solubility, molar weights, glass transition
temperatures & thermal stability, chromophore contents, and as well as from the point of view of their third-nonlinear
response. The third-order nonlinear absorptive and refractive effect of the polymers containing different substituted
azobenzene chromophores were investigated by the Z-scan technique. The effect of substituents on the azobenzene group
and the composition of the polymer chain were investigated by UV-Vis spectroscopy.
Colored micron-sized methyl methacrylate particles have been obtained by dispersion polymerization of methyl
methacrylate and an azo-monomer in the presence of vinyl silane oxazoline macromonomer used as stabilizer. The
polymerizable dye has a methacryloyl group for copolymerization and suitable azobenzene moiety to improve the
solubility in the solvent. The particles showed a spherical morphology and large size distribution, features which were
appreciated by scanning electron microscopy. The azo-dye could be covalently incorporated up to 4 wt% in the particles.
The thermal properties of the particles were investigated by simultaneous DSC-TGA analysis. The particles showed clear
Tgs at 128 °C and thermal stability up to 292 °C. The copolymer's chemical structures were confirmed by 1H-NMR and
FT-IR spectroscopy and their average molecular weights were evaluated by SEC.
We report the synthesis of five new hybrid polymeric structures obtained by free radical copolymerization of
some organic azo-based methacrylate monomers and 3-methacryloxypropyl trimethoxysilane (MEMO). The copolymers
are soluble in common solvents like methylene chloride, chloroform, dichlorbenzene, dimethylsulfoxide,
dimethylformamide. The copolymeric structures might be interesting from the point of view of nonlinear optical
response due to a rich content in chromophoric units determined by
H-NMR spectroscopy. The structures were also
characterized by FT-IR spectroscopy, TGA and SEC analysis.
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