3D Orientational Structures in Azopolymers Studied by UV Absorption Method

Yaroshchuk, O.; Tereshchenko, A. G.; Zakrevskyy, Yuriy; Shanski, I.

doi:10.1080/10587250108025737

Cited by 18 publications

(14 citation statements)

References 8 publications

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“…Analyzing various experimental approaches we concluded that the most efficient methods for this purpose are the methods operating with components of the refractive index tensor. The absorption methods are not universal but they can be successfully used in some experimental cases to estimate the components of order parameter tensor of azochromophores and other molecular fragments [3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Photoinduced 3D Orientational Order in Liquid Crystalline Azopolymers Studied by the Method of Attenuated Total Reflection

Yaroshchuk¹,

Bidna²,

Dumont³

et al. 2004

Molecular Crystals and Liquid Crystals

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The attenuated total reflection (ATR) technique is applied to study 3D ordering in the films of liquid crystalline (LC) polymers. We used a series of LC sidechain polyesters differing by the tail substitutes (NO 2 , OCH 3 and OC 4 H 9 ) in azochromophore. The 3D order is studied in non-irradiated films as well as in the films irradiated by polarized light with k ex1 ¼ 365 nm or=and with k ex2 ¼ 457 nm strictly distinguished by absorption efficiency of azochromophores. The orientation under irradiation is compared to that after irradiation. Biaxial, uniaxial as well as isotropic 3D ordering of azochromophores is realized. The observed uniaxial spatial structures can be classified by analogy with crystal optics; 1) positive C films with preferential out-of-plane orientation of azochromophores; 2) negative C films with in-plane random orientation of azochromophores having symmetry axis in the film normal direction; 3) positive A films with in-plane uniaxial orientation, and 4) negative A films characterized by oblate orientational distribution having symmetry axis in-plane of the film. The initial states as well as the stationary states of the films are characterized by uniaxial order of azochromophores, except in the case of intensive pumping with 365 nm, which results in isotropic ordering. The change of the tail substitute in the succession NO 2 ! OCH 3 ! OC 4 H 9 leads to orientation transition from the structure of negative C plate to the structure of positive C plate (non-irradiated films), increase of the tendency of isotropic ordering (k ex1 ¼ 365 nm irradiation), and transition from the The studies were supported by personal NATO grant for Dr. O. Yaroshchuk. structure of positive A plate to the structure of negative A plate (k ex2 ¼ 457 nm irradiation).

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Section: Introductionmentioning

confidence: 99%

Photoinduced 3D Orientational Order in Liquid Crystalline Azopolymers Studied by the Method of Attenuated Total Reflection

Yaroshchuk¹,

Bidna²,

Dumont³

et al. 2004

Molecular Crystals and Liquid Crystals

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“…Dependences δI E (1-3) and δI H (4, 5) on the time t, respectively, after the start of irradiation by a linearly polarized light with λ irr = 411 nm and after cessation of irradiation of specimens with the films of PA (1), PA-Ni(2,4), and PA-Co(3,5) at Θ = 90 o as well as dependences of δI E on Θ for specimens with films of PA (6), PA-Ni(7), and PA-Co (8) previously irradiated by a linearly polarized light with λ irr = 411 nm for 50 min. The vertical arrow indicates the moment of turning-off of the light with λ irr .…”

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confidence: 99%

“…with λ irr leading to the appearance and accumulation, in the polymeric films, of photoinduced dipoles of the isomers of azobenzene groups [4][5][6], which manifests itself in the appearance of a transient current pulse on the dependences of j d on t and in the increase of j d after irradiation of the specimens by light with λ irr (Fig. 1, curves 4-7).…”

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Electro- and Magneto-Optical Properties of Films of Polycomplexes of 4-Methacryloyloxy-(4′-Carboxy-3′-Oxy)Azobenzene with Metals

Давиденко

Savchenko

et al. 2005

J Appl Spectrosc

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The electrical conductivity, photoconductivity, and electrical and magneto-optical properties of the films of new polycomplexes of 4-methacryloyloxy-(4 ′ -carboxy-3 ′ -oxy)-azobenzene with nickel and cobalt have been investigated. The electrical conductivity and photoconductivity in the visible region of light are determined by the orientation effects of azobenzene groups as well as by generation and transfer of charge carriers between them. A change in the spatial orientation of photoinduced dipole moments of azobenzene groups in an external electric or magnetic field is attributed to the appearance of forces acting on electrically charged magnetic ions of a metal and that are rigidly connected with these groups.Introduction. Films of polymeric compositions with the monomers of azo dyes [1-3] or containing azobenzene side groups chemically bound with the base by a polymer chain [4][5][6] are of interest as optically active media. Under the action of a linearly polarized light, an induced polarization appears in them which at room temperature may persist for a rather long time. The induced polarization can change under the action of an external thermal or mechanical effect, on irradiation by light, and on superposition of an external electric or magnetic field. In an external field, rotation of the dipole moments occurs, and sometimes the effect of photoconductivity is observed, owing its origin to the photogeneration of charge carriers, which makes it possible to use such materials in xerography [6]. To enhance the influence of the magnetic field, polymeric compositions are prepared either on the basis of metal-containing monomers [7] or with addition of magnetic nanoparticles [8,9]. Since the mechanism of the effect of the electric and magnetic field is associated with the appearance of forces that rotate the dipole moments of azo compounds [10,11], an assumption suggests itself that the electro-optical and magneto-optical effects must manifest themselves in polymers with azo groups and ions of magnetic metals that are chemically bound with the polymer. Therefore, the aim of the present work is investigation of the electro-and photophysical properties of the films of such polycomplexes.Objects, Specimens, and Experimental Technique. For investigations we have synthesized for the first time the polymer poly-4-methacryloyloxy-(4 ′ -carboxy-3 ′ -oxy)azobenzene (PA) and polycomplexes 4-methacryloyloxy-(4 ′ -carboxy-3 ′ -oxy)azobenzene with nickel (PA-Ni) and cobalt (PA-Co), the structural formulas of which have the form

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“…Films of polymeric compositions ͑PCs͒ containing azobenzene dyes 1-3 or azobenzene lateral groups [4][5][6] are of interest for their application as optically active media, in particular, as polarization sensitive media for optical holographic recording. Induced polarization appears in the PC films under the influence of linearly polarized light which is absorbed by the azobenzene groups and causes changes of isomeric structures.…”

Section: Introductionmentioning

confidence: 99%

Electro-optical effect in films of azobenzene polycomplexes with cobalt

Davidenko

Давиденко

Savchenko

et al. 2008

Journal of Applied Physics

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Polymeric films containing azobenzene fragments with donor and acceptor groups were produced as well as films of polycomplexes of these fragments with cobalt. Absorption spectra of these films before and during application of an external electric field were investigated. Electro-optical properties of the films are conditioned by spatial reorientation of dipole moments of azobenzene groups induced by polarized light in an external electric field. Increase in dipole moments of azobenzene groups reduces the influence of cobalt ions on the electro-optical properties of the polycomplex films. In the proposed phenomenological model, the electro-optical effect is explained by effect of induced forces upon azobenzene isomers and metallic ions.

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3D Orientational Structures in Azopolymers Studied by UV Absorption Method

Cited by 18 publications

References 8 publications

Photoinduced 3D Orientational Order in Liquid Crystalline Azopolymers Studied by the Method of Attenuated Total Reflection

Photoinduced 3D Orientational Order in Liquid Crystalline Azopolymers Studied by the Method of Attenuated Total Reflection

Electro- and Magneto-Optical Properties of Films of Polycomplexes of 4-Methacryloyloxy-(4′-Carboxy-3′-Oxy)Azobenzene with Metals

Electro-optical effect in films of azobenzene polycomplexes with cobalt

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