Anton Airinei

Polyelectrolyte complexes. II. Specific aspects of the formation of polycation/dye/polyanion complexes

We report on the formation of the polycation/dye/polyanion (PC/D/PA) complexes by the interaction between nonstoichiometric polycation/dye (PC/D) complexes with polyanions. Polycations differed in their content of the (N,N-dimethyl-2-hydroxypropylene ammonium chloride) units in the main chain. Poly(sodium acrylate) (NaPA), poly(sodium 2-acrylamido-2-methylpropane sulfonate) (NaPAMPS) and poly(sodium styrenesulfonate) (NaPSS) were used as polyanions. Crystal Ponceau 6R (CP6R) and Ponceau 4R (P4R) with two or three sulfonic groups were used as anionic dyes. The interaction between nonstoichiometric PC/D complexes and polyanions was followed by UV-VIS spectroscopy, viscometry, and conductometry measurements. Formation of PC/D/PA complexes takes place mainly by the electrostatic interaction between the polyanion and the free positive charges of the nonstoichiometric PC/D complex. The stoichiometry and the stability of the tricomponent complexes depended on the polycation structure, the structure and molecular weight of polyanion, the dye structure, and the P/D molar ratio. A high amount of the dye was excluded from the complex before the end point when a branched polycation was used. The higher the solubility of the dye the lower the stability of the PC/D/PA complexes.

On the electrical properties of some modified polysulfones in thin films

Abstract The temperature dependence of the electrical conductivity and the Seebeck coefficient for some chelate-modified polysulfones (PSF-Cs) derived from chloro-terminated polysulfones and bis (2,4-dihydroxybenzaldehyde) Cu2+ were studied. The measurements were performed using the thin films deposited from solution. The investigated polymers have semiconducting properties. The correlations between these properties and the molecular structure of the respective polymers are discussed.

Optical properties of some new azo photoisomerizable bismaleimide derivatives.

Novel polythioetherimides bearing azobenzene moieties were synthesized from azobismaleimides and bis-2-mercaptoethylether. Kinetics of trans-cis photoisomerization and of thermal conversion of cis to trans isomeric forms were investigated in both polymer solution and poly(methyl methacrylate) doped films using electronic absorption spectroscopy. Thermal recovery kinetics is well described by a two-exponential relation both in solution and polymer matrix, while that of low molecular weight azobismaleimide fit a first-order equation. The photoinduced cis-trans isomerization by visible light of azobenzene chromophores was examined in solution and in polymer films. The rate of photoinduced recovery was very high for azobismaleimides.

Intermolecular interactions in solutions of some amino-nitro-benzene derivatives, studied by spectral means

The spectral shifts in the visible electronic absorption spectra of three amino-nitro-benzene derivatives in different solvents were correlated with the macroscopic parameters (refractive index and electric permittivity) of the solvents. The wavenumbers in the maximum of the visible charge transfer absorption band of o-nitro-aniline, 4-amino-3-nitrophenol and 3-amino-4-nitrophenol depend linearly on the Baur-Nicol function of electric permittivity. This dependence allows to estimate the electric polarizability in the electronic excited states if the electric polarizability in the ground state of the spectrally active molecule is determined by other procedures, such as by quanto-mechanical calculations.

Pendant functional group copolyether sulfones. II. Modified copolyether sulfones with aminoazobenzene units

Modified copolyether sulfones with bulky azo pendant groups were synthesized by a polycondensation reaction of some polysulfones containing aldehyde groups with p-aminoazobenzene. The corresponding model compound and an azo oligomer were also prepared to compare their properties. The structure of the resulting compounds was confirmed by IR, 1H-NMR spectra, and elemental analyses. The polymers were characterized by reduced viscosity, thermogravimetric analysis, and differential scanning calorimetry. The photochemical behavior of the azoaromatic chromophores was followed by UV-visible absorption spectroscopy. Two kinds of photoreactions (photoisomerization and photodecoloration) operate in these polymers.

Coordination Polymers. 9. Chelate Polymers Derived from Bisphenolic Complexes and Propylenediamine

Abstract Chelate polymers derived from bis(2,4-dihydroxybenzaldehyde)propyl-enediimine M and bis(2,4-dihydroxyacetophenone)propylenediimine M (M = Fe2+, Co2+, Ni2+, Cu2+, Zn2+) with aromatic acid chlorides were prepared by interfacial polycondensation. Also, chelate polysiloxanes were obtained from the same monomers and α,ω-dichloropolydimethyl-siloxane. The spectral, thermal, magnetic, and electrical properties of the polychelates were studied.

Solvent effects on the photophysical properties of poly[1,4-dihydroxyanthraquinoneimine-1,3-bis(phenylene-ester-methylene)tetramethyldisiloxane]

Absorption and fluorescence spectra of a polyquinoneimine, PQI, built on 1,4-dihydroxyanthraquinone and a siloxane diamine, 1,3-bis(amino-phenylene-ester-methylene)tetramethyldisiloxane, have been investigated in solvents of different polarities. The effect of solvents on the spectral properties was investigated using Lippert-Mataga and Bakhshiev polarity functions and Cataláns multiple linear regression approach. Absorption and fluorescence spectra in studied solvents exhibit hypsochromic and bathochromic shifts, respectively. The polarity of the solvent was the main parameter which changes the spectral properties of PQI. Also, the binary mixtures of chloroform with methanol and dimethyl sulfoxide were used to analyze the intermolecular interactions and preferential solvation. The preferential solvation parameters (local mole fraction (X₂(L)), excess function (δs₂) and preferential solvation constant (KPS)) were calculated from spectral data and discussed as a function of cosolvent content. The values of quantum yield, decreased linearly with increasing solvent polarity (for non-polar and polar solvents).

Molecular structure and modeling studies of azobenzene derivatives containing maleimide groups

The molecular orbital calculations have been carried out to investigate the structure and stability of (E) / (Z) isomers of some azobenzene derivatives containing maleimide groups. A special attention has been devoted to the compound (E)-1, (E)-1-(4-(phenyldiazenyl)phenyl)-1H-pyrrole-2,5-dione, for which the available crystallographic experimental data have been used to validate the modeling structures computed at the theoretical levels AM1, PM3, RHF/6-31+G(d,p) and B3LYP/6-31+G(d,p). To this end, the discrepancy between experimental and calculated structural parameters has been ascertained in terms of root-mean-square deviation (RMSD). The quantum calculations at the level RHF/6-31+G(d,p) yield the most accurate results on (E)-1 structure giving a deviation error from crystallographic data of about 5.00% for bond lengths and 0.97% for interatomic angles. The theoretical electronic absorption spectra of azobenzene derivatives of concern have been computed by means of configuration-interaction method (CI) at the level of semi-empirical Hamiltonians (AM1 and PM3). Likewise, the molecular energy spectra, electrostatic potential and some quantitative structure activity relationship (QSAR) properties of studied molecules have been computed and discussed in the paper.

Polyurethane cationomers with nitroazoaromatic groups

Novel polyurethane cationomers bearing p-nitroazoaromatic groups covalently incorporated in the polymer chain were synthesized. Their photobehavior in polymer films and solutions was investigated by electronic absorption spectroscopy and was also evaluated comparatively with an ionic azodiol model. Under UV irradiation, in the first stage of the photoprocess the trans-cis isomerization occurs, followed then by a photobleaching reaction in the second stage of the process.

A silicon-containing polyazomethine and derived metal complexes: synthesis, characterization, and evaluation of the properties

A new dialdehyde-containing silicon was prepared by a reaction of Williamson-type and structurally characterized. By its subsequent condensation with 2,5-bis(p-aminophenyl)-1,3,4-oxadiazole, a multifunctional polyazomethine-containing imine, phenylene, oxadiazole, ether, and carbosilane groups within the chain was prepared. The complexes of this polymer with Co(II), Cu(II), and Zn(II) ions formed on the basis of electron-donor ability of the oxadiazole and azomethine groups were prepared in a one-step approach by mixing the two precursors of polyazomethine (dialdehyde and diamine) with corresponding metal salt. The ligand and metal complexes were characterized by spectral (Fourier transform infrared (FTIR), 1H, and 13C NMR) methods. The thermal, optical, electrochemical, and dielectric properties were studied and the effects of the metal insertion in dependence on its nature over these properties were evaluated. All compounds are soluble in common organic solvents and show low glass transitions due to the flexible ether and Si–C bonds, are fluorescent, mainly due to the oxadiazole ring, are redox active and have high dielectric constant due to the presence of oxadiazole, azomethine metal units.