Thermochemically induced binding of methyl orange to polycations containing primary amine groups

The thermochemical transformation of electrostatically formed complexes of methyl orange (MO) with polycations containing primary amine groups such as ammonium salts afforded new polymers with a high concentration of covalently bound 4‐N,N‐dimethylaminoazobenzene groups in the side chain. Poly(allylamine hydrochloride) and poly(β‐aminoethylene acrylamide hydrochloride) were employed as support polycations for MO. The transformation of sulfonate–ammonium ion pairs into sulfonamide bonds, via heating at an elevated temperature, was supported by the polymer properties before and after the thermal treatment. The polymer structure changes were monitored with elemental analysis, Fourier transform infrared, ¹H NMR, and ultraviolet–visible absorption spectroscopy, and thermogravimetric analysis. The spacer length between the backbone and azobenzene structures used as side chains strongly influenced the polymer properties before and after the heat‐induced reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5898–5908, 2006     

Determination of the kinetic parameters of polyvinylchloride

Kinetic equations proposed in the literature for thermal decomposition reactions may be approximated at low conversions by the relation: ^b=Dp(x). This equation reveals three kinds of behaviour under isothermal conditions, as evidenced in the thermal dehydrochlorination of Polyvinylchloride. The kinetic parameters were determined with a computing program and its performances were tested. The calculation method was applied to some Polyvinylchloride macromodels.

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Zusammenfassung In der Literatur vorgeschlagene kinetische Gleichungen für thermische Zersetzungsreaktionen können bei niedrigen Konversionen mit der Gleichung ^b=Dp(x) genähert werden. Diese Gleichung offenbart unter isothermen Bedingungen drei Verhaltensweisen, wie an der thermischen Dehydrochlorierung von Polyvinylchlorid bewiesen wird. Die kinetischen Parameter wurden mittels eines Computerprogrammes ermittelt und ihre Leistungsfähigkeit überprüft. Das Rechenverfahren wurden an einigen Polyvinylchloridmakromodellen getestet.

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, , ^b =Dp(x). , . , . .

     

Photoisomerization of AZO Aromatic Chromophobes in Polyvinyl Chloride

Abstract

The synthesis and characterization of new vinyl chloride-p-acryloyloxyazobenzene copolymers are reported. Kinetics of photoinduced trans-cis and thermal cis-trans isomerization of azo pendant groups in copolymer have also been investigated, and the kinetic parameters were evaluated. An azo acrylate model compound was used for comparison.     

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

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.     

Silicone composites containing stabilized silver clusters or nanoparticles

Silver nanoparticles are of high importance due to their electrical, magnetic, and optical properties, as well as catalytic and biocidal activity that are superior to the bulk silver and other metals. To prepare certain devices, generally, silver is incorporated into a matrix either as preformed or in situ‐generated particles. Silver nanoparticles were generated in situ into a silicone matrix formed by cohydrolysis of the mixture of silanes, each of them having a certain role: dimethyldiethoxysilane (DMDES) as a precursor for highly flexible polydimethylsiloxane, methyltriethoxysilane (MTES) as a cross‐linker highly compatible with polydimethylsiloxane, and 3‐aminopropyltriethoxysilane as a stabilizer, since it can readily complex to silver atoms through its amine functionality. Dimethylformamide (DMF) was used as a solvent for the silver nitrate and reducing agent. The samples were investigated both in sol state and as aged coating films deposited on glass substrate. The complexation of the silver and the matrix formation were emphasized by FTIR. The size of the formed silicone particles encapsulating silver was estimated by dynamic light scattering (DLS) (about 100 nm) in sol and by AFM in film (about 90 nm). The formation of the clusters or nanoparticles depending on the ratio between the reducing and complexing agents was evidenced by UV–Vis absorption spectra. Thus, it would create conditions to stop and isolate clusters at the desired size by precise control of the experimental conditions. The composites could be used alone as antibacterial‐coating materials but also, porous silica having incorporated silver clusters with potential applicability in catalysis may result after their calcination. Copyright © 2010 John Wiley & Sons, Ltd.     

On the compatibility of binary and ternary random copolymers of acrylonitrile with vinyl acetate and/or α-methylstyrene—II: The influence of the time factor

The time dependence of the microscopical aspect, crystallinity, viscosity of the spinning solutions and the thermal and tinctorial properties of films formed from binary, ternary copolymers and binary copolymer mixtures of acrylonitrile with vinyl acetate and χ-methylstyrene have been compared. The characteristics of binary copolymers and incompatible mixtures are stable with time, while those of ternary copolymers and pseudocompatible mixtures evolve towards a limiting state. with phase separation.     

Multifunctional materials based on polyazomethines derived from 2,5‐dihydroxy‐1,4‐benzoquinone and siloxane diamines

New polyazomethines have been synthesized by the reaction between 2,5‐dihydroxy‐1,4‐benzoquinone and siloxane diamines differing by the siloxane sequence length. A dimer has also been prepared as a model compound. The products were characterized by spectral (FTIR and ¹H‐NMR) and elemental analyses, GPC, viscosity measurements, solubility tests, and transmission electron microscopy (TEM). The different properties have been investigated by adequate techniques: thermal (DSC and TGA), spectral (UV–vis and fluorescence spectroscopy), redox (Differential Pulse Voltammetry). pH‐sensitivity and metal complexing ability were also evaluated. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1862–1872, 2008     

Fluorescence Modulation and Photochromism in Azobismaleimide Derivatives

A fluorophore-photochrome system incorporating an aryleneimine type fluorophore and an azobismaleimide photochrome was developed and the photochemical properties of this system were investigated. The photoisomerization of trans-azoaromatic chromophore leads to the increase of the fluorescence intensity of fluorophore. The cis azobismaleimide isomers revert photochemically to the trans form and the emission intensity decreases. The fluorescence intensity of the imine fluorophore can be modulated under irradiation with UV and visible (436 nm) light due to reversible trans-cis-trans photoisomerization of azobismaleimide partner. The photoisomerization kinetics was obeyed a first-order relationship with a rate constant of 1.95?×?10^?2 s^?1 for azobismaleimide/imine fluorophore system and for polyazothioetherimide/imine derivative the kinetics was described by a biexponential equation.     

1,3,4-Oxadiazole Derivatives. Optical Properties in Pure and Mixed Solvents

1,3,4-Oxadiazole derivatives-organic materials are an interesting and continuously developing area of research. This review describes some optical properties and highlights the current applications of these compounds in biomedical and optoelectronic fields. The relationships between polymer structures, environmental factors and optical properties (absorption and fluorescence) of several selected and relevant l,3,4-oxadiazole-containing molecules were presented in this review. These aspects were analyzed in various pure solvents and microheterogeneous media (mixed solvents). Also, the selectivity and sensitivity of some 1,3,4-oxadiazole derivatives-organic materials for different metal ions were discussed and evaluated by using spectral techniques. Finally, some important photophysical characteristics of 34 series of organic materials containing ?1,3,4-oxadiazole rings, were collected in a table.     

Electronic and Optical Properties of Some Polysulfone-Polydimethylsiloxane Copolymers in Thin Films

Polysulfone (PSF)-polydimethylsiloxane (PDMS) block copolymers (PSF-b-PDMS) with various compositions were prepared by condensing chloro-terminated polysulfone oligomers with α, ω -dihydrogensilyl-polydimethylsiloxane in refluxing chlorobenzene solution in the presence of urea as a hydrogen chloride acceptor. The temperature dependences of the electrical conductivity and thermoelectric power (Seebeck coefficient) of copolymers were studied using thin films deposited from a dimethylformamide solution (spin coating method) onto glass substrates. It was established that the various copolymers showed typical semiconducting properties. Some correlations between these properties (activation energy, ratio of carrier mobilities, etc) and molecular structure of the copolymers were found. A model based on band gap representation was found to be suitable for explanation of the electronic transport mechanism through the studied copolymers in thin films. The study of the transmission and absorption spectra (in the spectral range from 300 nm to 1400 nm) evidenced that the indirect allowed optical transitions were predominant. The values of the optical energy band gap (ranged between 1.50 eV and 1.70 eV) are in agreement with values of width of the forbidden band calculated from the temperature dependence of the electrical conductivity.