Coordination polymers. XV. Influence of diols on the reaction between unsaturated polyesters and Mg ions

An increase in viscosity of reaction mixtures of low molecular mass, COOH, and alcoholic OH-terminated polyesters with MgO is considerably reduced by the presence of diols in the system. This effect is analogous with that described for the presence of water. Joint presence of water and diol results in an additive effect. The mechanism of this effect can be interpreted by coordination chemistry. In this system both diol and water saturate the coordination sphere of Mg²⁺ ion (as ligands). Consequently, the coordination of donor groups of polyester (terminal OH and ester carbonyl groups) is suppressed by reducing the extent of linking the polyester molecules with coordination bonds; that is, the average molecular mass of the system. Moreover, coordination of low-molecular ligands modifies the final molecular structure that occurs in the system. In addition, some kinetic effects are revealed in the process because the system is diffusion-controlled by the ever-increasing viscosity. This effect is also favorable to the coordination of low molecular mass ligands. All of these factors lead to a reduction in the increase of viscosity in the present system.     

Coordination polymers. VIII. IR spectroscopic studies on the mechanism of the reaction between polyesters and zinc oxide

This article was written for the purpose of investigating the mechanisms of reactions between unsaturated polyester resins and base anhydridelike metal oxides (CaO, MgO, ZnO) which cause an increase in viscosity. As a model system ethyl-hydrogen-succinate (ESH) and ZnO were reacted in CCl₄ and complexes that contained Zn-hydroxocarboxylate units took an essential part in this reaction. Solubility measurements of the model compounds and infrared (IR) spectra of the reaction products led to the conclusion that further molecular associates were formed from the mixed metal-hydroxocarboxylate complex by the carbonyl oxygens of ester groups, which resulted in end products of polymeric structure. It is suggested by IR spectroscopical analogies between the model compounds and reaction products of an adipic acid/butanediol-1,4 polyester with ZnO that similar reactions can account for the polyesters as well.     

Dta study of the reactions of V2O5 with metal (II) oxides

The “Ignition” criteria taken from the theory of combustion are suggested for the determination of various kinetic characteristics with the thermophysical parameters depending upon the temperature. The result of application of the “Ignition” criteria to determine the activation energy of magnesite are presented. It is shown that on taking into account a linear relationship between the temperature and the heat capacity and the heat conductions of magnesite and the reference materialE proves to be much lower than the value of activation energy obtained with the assumption that the thermophysical parameters do not depend on it.     

Studies on coordination polymers : Part II. Coordination polymers of 1,6-dihydroxyphenazine

Coordination polymers of 1, 6-dihydroxyphenazine (I) with Cu(II), Zn(II), Ni (II), Co(II) and Hg(II) were prepared and studied. All the polymers formed were dark blue to black powders, very insoluble in the common solvents, apparently of low molecular weight, and decomposed at temperatures ranging from 200 to 280°. The zinc polymer was the most stable, mercury the least. Infrared studies confirmed the proposed chelation reaction between the metal ion and (I). The polymers of Co and Hg were amorphous, whereas those of Cu, Zn, and Ni were crystalline. When used as a spot test reagent, (I) gave instant color reactions with 15 common ions but neither the sensitivity nor selectivity of the reagent is impressive.     

The evolution of toxic gases from heated polymers—II. Nitrogen oxides

Various polymeric materials commonly used domestically have been subjected to temperatures ranging from 600 to 1000° under laboratory conditions and the amounts of nitrogen oxides evolved have been measured. In general, the amounts formed are small (from 0·2 to 2·0 per cent calculated on the original weight of sample). The results show little dependence on the nitrogen content of the sample.     

Chromato-mass spectral study of the reactions of organylsiloxanes with metal oxides

A study was carried out on the reaction of 1,1,3,3-tetramethyldisiloxane with metal oxides such as CuO, HgO, and Sb₂O₅ in the presence of compounds containing a siloxane bond such as hexamethyldisiloxane, octamethylcyclotetrasiloxane, and trimethylacetoxysilane, which, at 100–110°C over 0.5–10 h, leads to the formation of linear organyl siloxanes (CH₃-[-Si(CH₃)₂O-]_n-Si(CH₃)₃, CH₃-[-Si(CH₃)₂O-]_n-Si (CH₃)₂H, and H-[-Si(CH₃)₂O-]_n-Si(CH₃)₂H, where n=2–6, and cyclic organylsiloxanes. The reaction does not proceed in the presence of aluminum, bismuth, germanium, and lead oxides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1658–1660, July, 1990.     

Biodegradable polymers based on renewable resources. II. Synthesis and biodegradability of polyesters containing furan rings

A series of polyesters were synthesized by the bulk polycondensations of the respective combinations of two difuranic diesters, i.e., bis(5-(methoxycarbonyl)-2-furyl)methane ( 4a ) and 1,1-bis(5-(methoxycarbonyl)-2-furyl)ethane ( 4b ), with two 1,4 : 3,6-dianhydrohexitols [1,4 : 3,6-dianhydro-D -glucitol ( 1 ) and 1,4 : 3,6-dianhydro-D -mannitol ( 2 )], four aliphatic diols, and three oligo(ethylene glycol)s. The polycondensations were carried out at 220–230°C in the presence of titanium isopropoxide as a catalyst, giving polyesters having number average molecular weight up to 2.4 × 10⁴. These polyesters are soluble in a variety of solvents including chlorinated hydrocarbons, 1,4-dioxane, dimethyl sulfoxide, dimethylformamide, and sulfolane. Soil-burial tests along with enzymatic degradation experiments showed that these polyesters are potentially biodegradable. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2729–2737, 1997     

Response of semiconducting metal oxides to water vapor as a result of water molecules chemical transformations on catalytically active surfaces

The sensitivity (response) of six semiconducting metal oxide (SMO) structures on the basis of SnO₂ to water vapor was studied in dry and humid air over the H₂O vapor concentration range 0–2.9 vol % (0–100% RH) as the temperature of the samples changed from 200 to 600°C. The temperature dependence of the conductivity and response of SMOs to H₂O vapor had extrema at 300–400 and 250–400°C, respectively, and the sensitivity to water vapor did not decrease below 1.7–1.9 up to 600°C. Data on changes in the conductivity of SMOs and the number of OH⁻ groups in the oxygen-hydroxyl layer on the surface of SMOs depending on temperature and air humidity were obtained. A sharp change in conductivity as air humidity increased from 0 to 10% RH could be related to either a sharp change in the number of OH⁻ groups in the oxygen-hydroxyl layer because of the high polarity of water molecules or a decrease in the intergrain energy barrier. The phenomena observed and the behavior of SMO conductivity in dry and humid air were interpreted. The experimental data were used to suggest a mechanism of the formation of hydroxyl groups on the surface of SMOs. The paper contains practical recommendations concerning the temperature conditions under which the influence of humidity on changes in the conductivity of SMOs is weakest.     

Hydroxamic acid polymers. Effect of structure on the chelation of iron in water: II

The effect of structure on the ability of hydroxamic acid polymers to chelate iron(III) was examined. The polymers were derived from acryloyl or methacryloyl backbones that bore side chains terminated in hydroxamic acids. The side chain length, which establishes the atomic chain distances between hydroxamic acid groups, had the most pronounced effect on the stability constant of the iron chelate. It was this atomic chain distance that determined how easily the three neighboring hydroxamic acids could fit the octahedral sphere of the iron. Other structural changes such as the presence or absence of methyl groups on the backbone or on the hydroxamic acid nitrogen had little measurable effect. The stability of the iron complexes appeared to be optimum at an 11-atom spacing between hydroxamic acids and decreased with shorter or longer spacing distances.     

Effect of metal oxides on the reforming of methane with carbon dioxide

The effect of basic and rare earth metal oxides on the stability of nickel-based catalysts for the CO₂ reforming of CH₄ has been studied. The addition of metal oxides increased the stability of Ni-based catalysts and reversed the values of the reaction orders with respect to both CH₄ and CO₂. In the presence of metal oxides, the values of the reaction orders with respect to CO₂ partial pressure followed the same trend of catalyst stability.     

Functional monomers and polymers. LXXXVI. Photochemical reactions on synthetic polymers with pendant thymine bases: Effect of solvents

Photodimerization of thymine bases present on the side chain of acryloyl and methacryloyl-type polymers was studied in dimethyl sulfoxide, dimethylformamide, and dimethyl sulfoxide—ethylene glycol mixture. Quantum efficiencies for photodimerization and quenching with isoprene were influenced by the solvents. The self-association of thymine bases estimated from their ultraviolet (UV) spectra and intrinsic viscosity were related to the effect of solvent on the photodimerization.     

Surface modification of polymers. II. Grafting with glycidyl acrylates and the reactions of the grafted surfaces with amines

The surface of low density polyethylene has been grafted with glycidyl acrylate and glycidyl methacrylate by photoinitiation. ESCA measurements on the grafted surface showed a 72% coverage for glycidyl acrylate and 52% for glycidyl methacrylate after 10 min of grafting with UV irradiation. ATR–IR showed a 10 times more extensive grafting for glycidyl acrylate than for glycidyl methacrylate after 10 min of grafting, indicating reaction to deeper layers. Acetone and ethanol were used as solvents: acetone yielded slightly more grafting at the surface. The grafted surfaces were reacted with 2M solutions of aniline and propylamine in ethanol. After 4 h reaction at 60°C, with aniline 52% of the epoxy groups while for propylamine 96% of the groups were consumed, as measured with ATR–IR.     

Chelate polymers: II. Some novel transition metals complexes with azomethine‐containing siloxanes and their polyesters

New Schiff bases of 2,4‐dihydroxybenzaldehyde with siloxane‐α,ω‐diamines having different numbers of siloxane units in the chain have been synthesized and characterized by spectroscopy, elemental and thermal analyses. These azomethines were found to form complexes readily with copper(II), nickel(II), cobalt(II), cadmium(II) and zinc(II). From IR and UV–Vis studies, the phenolic oxygen and imine nitrogen of the ligand were found to be the coordination sites. Thermogravimetric analysis (TGA) data indicate the chelates to be more stable than the corresponding ligands. The melting points increase with shortening of the siloxane segment from azomethine, as well as the result of complexation. The chelates obtained were covalently inserted in polymeric linear structures by polycondensation through the OH‐difunctionalized ligand with 1,3‐bis(carboxypropyl)tetramethyldisiloxane. Direct polycondensation, assisted either by acetic anhydride or N,N′‐dicyclohexylcarbodiimide as dehydrating agent and the complex 4‐(dimethylamino)pyridinium 4‐toluenesulfonate as catalyst, was used for the synthesis of these compound types. The structures of the polymers obtained were confirmed by IR, UV and ¹H NMR. Characterization was undertaken by TGA, solubility tests and viscosity measurements. Copyright © 2003 John Wiley & Sons, Ltd.     

Investigation of the influence of metal oxides on the thermal degradation of chlorine-containing polymers by thermogravimetry

The influence of oxides of zinc, magnesium, antimony and aluminium on the thermal degradations of polychloroprene, chlorinated polyethylene and epichlorhydrin homopolymer has been investigated. The investigations showed that these metal oxides can change the thermal stabilities and degradation processes of chlorine-containing polymers. A considerable acceleration of the dehydrochlorination of these polymers was found in the presence of zinc oxide.

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Zusammenfassung Es wurde der Einfluß von Zink-, Magnesium-, Antimon- und Aluminiumoxid auf den thermischen Zerfall von Polychloropren, chloriertem Polyäthylen und Epichlorhydrin-homopolymeren untersucht. Die Untersuchungen zeigen, daß diese Metalloxide die thermische Stabilität und die Zersetzungsprozesse von chlorhaltigen Polymeren verändern können. In Gegenwart von Zinkoxid wurde eine bedeutende Beschleunigung der Dehydrochlorierung dieser Polymere festgestellt.

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Quantum-mechanical study of the reaction of metal and halide ions with water molecules

Journal of Structural Chemistry -     

Effect of metal oxides on the gamma radiolysis of ammonium nitrate

The studies of radiation decomposition of ammonium nitrate in the presence of MnO₂, PbO and V₂O₅ with the absorbed dose reveal that MnO₂ retards while PbO and V₂O₅ accelerate the rate of radiolysis. G/NO ₂ ^– / values were found to increase with the mole% of V₂O₅ in an admixture. The results are explained on the basis of electron donor-acceptor properties of oxides affecting the equilibrium concentration of electrons present in pure ammonium nitrate in the presence of the added oxides.     

Effect of birefringence on the scattering of light. II. Oriented polymers

It has been considered for some time that the presence of birefringence in an oriented polymer must affect the light-scattering behavior. Previous analyses of this phenomenon are restricted to single-particle scattering. A more complete theory of the effect of birefringence on the scattering of light from correlated systems is presented. The measured scattering intensity is shown to be dependent upon the optical properties of the sample as well as the experimental technique and conditions.