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

Abstract

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

Synthesis and Electrooptical Properties of Metal-Containing Azopolymers. The Influence of Steric Factors on the Electro-Optical Effect in Polycomplexes of Azobenzene Derivatives with Cobalt

“…The electric field had a more appreciable effect on the light transmission when the samples were pre irradiated by polarized light in the absorption range of azobenzene groups (k < 550 nm). The most significant change in I 0 induced by an external electric field is observed after exposure of the samples to light transmitted through the polarizer (exposure time t > 30 s) and when an analyzer with h ¼ p=2 is used [7]. Figure 1 shows the dependences of dI E on k, measured for h ¼ p=2 after a long-term exposure of the samples by polarized light with k < 550 nm.…”

“…In the latter case the sample was located between two polarizers at an angle of ninety degrees. The electric field (E ¼ 1 Â 10 8 V=m) was produced by the corona discharge [7]. The value dI E was determined in dependence on time (t) of the illumination with polarized light and after this illumination, light wavelength k, angle h between directions of polarized axes of the polarizer and analyzer.…”

Electro-optical effect in films of azobenzene polycomplexes with cobalt

“…The most intensive changes of I 0 in applied electric field happen after illumination of the samples with polarized light for t Ͼ 30 min for analyzer angle = / 2. 12 The experimental spectral dependencies of ␦I E after quite a long illumination of the samples with polarized light with Ͻ550 nm are shown in Fig. 4 ͑ = / 2͒.…”

Films made of substituted azobenzene polycomplexes with cobalt for polarization holography

“…Films of polymer composites with azo dye monomers or containing azobenzene side groups chemically bonded to the polymer backbone have optically active properties, which can be used to design electro-optical light modulators [1,2] and holographic recording media [3][4][5][6][7]. When these films are exposed to linearly polarized light, photoinduced optical anisotropy appears, which is caused by a change in the concentrations of trans and cis isomers of the azobenzene groups.…”

“…This effect is a determining factor for using the materials under consideration as recording media for polarization holography [4][5][6][7], in which extremely high information recording density can be achieved [8]. Reorientation of photoinduced dipole moments of the isomers of the azobenzene groups when exposed to an external electric or magnetic field is determined by the presence of metal ions within the films [1,9,10]. The latter indicates that azobenzene polycomplexes with metals may be new polarization holographic media, the characteristics of which change when exposed to an external electric or magnetic field.…”