Synthesis and photophysical properties of soluble polyimides and polyquinazolones containing side-chain chalcones or azo chromophores

Soluble aromatic and carboxyl- and hydroxyl-containing polyimides, mixed polyimides, and polyquinazolones of various chemical structures, as well as a series of new dicyanoazobenzene chromophores, are synthesized. From 20 to 80 mol % of chromophore groups are incorporated into side chains of the polymers. The thermal, photosensitive, and nonlinear optical properties (second-harmonic generation) of the chromophore-containing polymers are investigated. The polymers with covalently attached groups of the dye DR-13 or azo-derivatives of 4-phthalonitrile demonstrate the highest nonlinearity. The T _g values of the polyimides vary from 165 to 215°C; their temperatures corresponding to 5% weight loss lie in the range 290–350°C; and the measured coefficients of second-harmonic generation, d ₃₃, for a number of polarized films based on chromophore-containing polymers attain several tens of picometers per volt. The incorporation of chromophore groups into the side chains of the polymers causes an increase in the photosensitivity of polyimides by an order of magnitude relative to that of the parent polymers (S _0.1 = (3?4) × 10⁵ cm²/J in the range of dye absorption).     

Synthesis of heterocyclic compounds using oxaloacetic ester (review)

Published data on the use of oxaloacetic ester in the synthesis of various heterocyclic systems are discussed. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 163–187, February, 2008.     

Feature of kinematic diffraction of nonmonochromatic divergent X-ray beams in a crystal with a periodically strained lattice

Coherent scattering of a nonmonochromatic divergent beam of X-ray quanta in a crystal excited by an acoustic wave is described using a kinematic approach. The possibility of manifestation of a peculiar effect of amplification of the diffracted X-ray beam by the acoustic wave is predicted using this approach.     

On the Applicability of the Relations of the Cubic Timoshenko-Type Theory of Shells to the Study of the Postcritical Behavior of Rods

The question of whether the nonlinear Timoshenko-type theory of shells can be applied to the study of the initial postcritical behavior of a rod under compression is considered. The Koiter asymptotic theory in the Budyanskii form is used. The exact solution of the problem is obtained and a formula for the coefficient of postcritical behavior allowing for the effect of lateral-shear strains is derived. It is shown that the expressions (specified to within cubic terms) for lateral-shear strains and curvature permit us to use the nonlinear theory of shells to analyze the initial supercritical behavior of rods     

Dynamic spectral response of solid solutions of the bismuth-strontium ferrite Bi1 − x Sr x FeO3 − δ in the frequency range 0.3–200 THz

Ceramic samples of Bi_{1 ? x} Sr _x FeO_{3 ? δ} have been investigated using X-ray diffraction analysis, Raman spectroscopy, and infrared spectroscopy. It has been shown that the spectra of these solid solutions should be considered as a superposition of resonant phonon responses of the cubic perovskite and a relaxation response. No relaxators are observed in the pure compounds BiFeO₃ and SrFeO_{3 ? δ}. It has been found that two concentration phase transitions occurs with the symmetry changes $R3c \leftrightarrow Pm\bar 3m$ in the range 0.1 < x < 0.2 and $Pm\bar 3m \leftrightarrow P4mm$ in the range 0.8 < x < 1.0.     

Influence of the Mechanical and Geometric Parameters of Composite Cylindrical Shells with Local Deflection on the Behavior of the Equilibrium Curves Under Axial Compression

International Applied Mechanics - A procedure for analytical solution of the problem of the stability and post-buckling behavior of composite cylindrical shells with local deflection under axial...     

Synthesis of Ethyl 2,2-Bis{[(benzoylcarbamothioyl)oxy]methyl}propanoate and Its Complexes with Copper(II) and Cobalt(II) Ions

Russian Journal of General Chemistry - The structures of ethyl 2,2-bis{[(benzoylcarbamothioyl)oxy]methyl}propanoate and its 1 : 1 complexes with copper(II) and cobalt(II) ions were determined by...