Thermal properties of poly-N-vinylcarbazole derivatives

Thermal studies were carried out on some products of chemical modification of poly-N-vinylcarbazole (PNVC). The effect of a substituent introduced into the carbazole ring on the thermal stability of the polymers was investigated. The kinetic parameters of the thermal degradation process were computed.

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Zusammenfassung An chemisch modifizierten Produkten von Poly-N-Vinylkarbazol (PNVC) wurden thermische Untersuchungen durchgeführt, sowie der Effekt eines in den Karbazolring eingeführten Substituenten auf die thermische Stabilität des Polymers untersucht. Weiterhin wurden die kinetischen Parameter des Zersetzungsprozesses errechnet.

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Thermal behaviour and adsorption properties of some benzothiazole derivatives

The thermal stability and the adsorption properties have been investigated for three benzothiazole compounds: 2-mercaptobenzothiazole (MBT), N-cyclohexyl-2-benzothiazole sulfenamide (NCBSA), and 2,2′-dibenzothiazole disulphide (BTD), reported in our early studies as corrosion inhibitors for carbon steel in different media. The electrochemical results were used to calculate the degree of surface coverage (θ). The adsorption mechanism of the three inhibitors was discussed according to the free energy of adsorption ( \( \Delta G_{{\text{ads}}}^{\circ } \) ) value obtained from Temkin adsorption isotherm, this being the best way to quantitatively express the adsorption process of their molecules on carbon steel surface. Thus, a mixed type mechanism involving the synergism between physisorption and chemisorption was proposed. The thermal analysis curves showed that, for the occurred events up to 470 °C, mass losses take place with endothermic effects followed by the total oxidation of the residue with an exothermic effect around 520 °C. Consequently, their effectiveness follows the order: BTD > NCBSA ≥ MBT, while the thermal stability ranges as follows: NCBSA < BTD ≤ MBT.     

Thermal and electrical properties of porphyrin derivatives and their relevance for molecule interferometry

The authors present new measurements of thermal and electrical properties for two porphyrin derivatives. They determine their sublimation enthalpy from the temperature dependence of the effusive beam intensity. The authors study H2TPP and Fe(TPP)Cl in matter-wave interferometry. Both molecules have nearly equal de Broglie wavelengths but different internal characteristics: only Fe(TPP)Cl exhibits an electric dipole moment of about 2.7 D and the authors discuss its influence on the molecular interference pattern. The authors add an external electric force field to the interferometer and use it to measure the scalar polarizability. They compare their experimental values alpha(H2TPP)=105+/-4+/-6 A3 and alpha(Fe(TPP)Cl)=102+/-9+/-6 A3 to ab initio calculations and they discuss the influence of thermal excitations on the polarizability.     

Thermal isomerization of dewarbenzene derivatives

The rates of thermal conversion of seven simple dewarbenzene derivatives to their corresponding benzene isomers were measured. Relatively minor substituent changes were found to have profound effects; isomerization rates increased with the number and strength of electron-withdrawing moieties. Surprisingly, the rate of thermal isomerization for one derivative was the same in fluid solution as in a solid polymer matrix, suggesting that this reaction has a low volume of activation. Other preliminary experiments suggest that the putative intermediate has some polar character. These data may provide some insights into the reaction mechanism.     

Thermal decomposition of N-fluoroazoxy derivatives

Conclusions The kinetics of the thermal decomposition of 2-nitro- and 2-difluoroamino-2-N-difluoro-azoxypropane, members of the class of N-fluoroazoxyalkanes, were investigated. It was shown that the reaction takes place in the gas phase according to a molecular mechanism through a six-site activated complex. The NF₂ group in the position affects the decomposition of the N-fluoroazoxy group more strongly than NO₂.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1721–1724, August, 1984.     

Thermal properties of oxide

To evaluate the thermal stability of oxide glasses, various criteria have been used. Not only the simple parameters, as characteristic temperatures and values of activation energy and enthalpy changes, but also the combined criteria E/RTp and kf(T) have been taken into account. Three glasses with the composition of Li₂O·2SiO₂ (a), Li₂O_·2SiO₂·0.03TiO₂ (b) and Li₂O·2SiO₂·0.1TiO₂ (c) were prepared and the validity of the criteria was tested by applying them to these glasses. The results indicate that the sequence thermal stability of the studied glass system vs. crystallization depends not only on their composition but also on the used criteria. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal properties of biocomposites

Thermal properties of new biocomposites prepared from modified starch matrix reinforced with natural vegetable fibres were studied. DSC and TG methods were applied to study thermal behaviour of biocomposites. Biocomposites were obtained in the laboratory twin-screw extruder. Two kinds of natural fibres were used, i.e. flax and cellulose in the amount of 0–40 mass%. DSC curves of biocomposites reveal glass transition temperature, attributed to the amorphous nature of the plasticized starch matrix. In general, incorporating natural fibres into modified starch matrix leads to an increase in glass transition temperature. Thermal degradation of modified starch matrix and cellulose reinforced biocomposites proceeds in three steps, whereas the degradation process of flax reinforced biocomposites occurs in two steps. For unreinforced matrix as well as for all biocomposites, regardless of type and amount of reinforcement, the major mass loss is observed at the temperature above 300°C. The increase in thermal stability with introduction of natural fibre is observed for both flax and cellulose reinforced biocomposites.     

Thermal properties of polylactides

A thermal analysis of a series of polylactides (PLA) was carried out based on the number of average molecular mass (M _n), and the nature of isomer (D, L and DL). It is confirmed that the glass transition temperature (T _g) of PLA increased as a function of molecular mass irrespective of isomer type except sample with a high polydispersity index. The melting temperature (T _m) and enthalpy of crystal fusion (ΔH _f) of L-isomer increased as the M _n was increased from 1100 to 27500. The degree of crystallinity (χ_c%) increased as a function of molecular mass. However no crystallization peak was detected in the lower molecular mass range (550–1400). The non-isothermal crystallization behavior of the PLA melt was significantly influenced by the cooling rate. Both D and L isomers exhibited insignificant difference in thermal properties and DL lactides exhibited amorphous behavior at identical molecular masses. Change in microstructure showed significant difference between two isomers. Analysis of the FTIR spectra of these PLA samples in the range of 1200–1230 cm⁻¹ supported DSC observation on crystallinity.     

Thermal stability and degradation of starch derivatives

Thermal behaviour of different starch derivatives, i.e. starch esters and ethers having degree of substitution (DS) in the range of 0.02–0.18 were studied. Potato, maize and wheat starches were used. Measurements were carried out by coupled thermal analysis/ mass spectrometry method (STA-MS) in air atmosphere. The major DTG peak during the investigation for starch derivatives is observed below 300°C. The mass loss up to a temperature of 300°C is about 50%. The most abundant ions found areH₂O⁺ and CO₂ ⁺. For the studied starch derivatives with a low degree of substitution (DS<0.18) no correlation was found between thermal stability and the level of substitution regardless of the nature of substitution.     

Thermal properties of pentavanadates

The thermal properties of K₃V₅O₁₄,Rb₃V₅O₁₄ and Tl₃V₅O₁₄ were studied in the temperature range 20–1000 in air atmosphere using DTA. K₃V₅O₁₄, is the most stable pentavanadate. Tl₃V₅O₁₄ is thermally stable up to 360; at higher temperature it decomposes to TlVO₃ and Tl₂V₆O₁₆. Rb₃V₅O₁₄ is stable up to 300 at higher temperature it decomposes to RbVO₃ and Rb₂V₆O₁₆, and at even higher temperature Rb₂V₆O₁₆, reacts with part of the RbVO₃ and Rb₂V₄O₁₁ is formed.

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Zusammenfassung Die thermischen Eigenschaften von K₃V₅O₁₄, Rb₃V₅O₁₄ und T1₃V₅O₁₄ wurden im Temperaturbereich von 20 bis 1000 in Luft durch DTA untersucht. K₃V₅O₁₄ ist das stabilste Pentavanadat. Tl₃V₅O₁₄ ist thermostabil bis zu 360; bei höheren Temperaturen wird es zu TlVO₃ und Tl₂V₆O₁₆ zerstetzt. Rb₃V₅O₁₄ ist bis zu 300 stabil, bei höheren Temperaturen wird es zu RbVO₃ und Rb₂V₆O₁₆ zersetzt und bei noch höheren Temperaturen reagiert Rb₂V₆O₁₆ mit einem Teil des RbVO₃ zu Rb₂V₄O₁₁.

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Résumé On a étudié les propriétés thermiques de K₃V₅O₁₄, Rb₃V₅O₁₄ et Tl₃V₅O₁₄ par ATD entre 20 et 1000 dans l'air. K₃V₅O₁₄ est le pentavanadate le plus stable. Tl₃V₅O₁₄ est thermiquement stable jusqu'à 360; à des températures plus élevées il se décompose en TlVO₃ et Tl₂V₆O₁₆ · Rb₃V₅O₁₄ est stable jusqu'à 300; à des températures plus élevées il se décompose en RbVO₃ et Rb₂V₆O₁₆ et à des températures encore plus élevées, Rb₂V₆O₁₆ réagit avec une partie du RbVO₃ et il se forme Rb₂V₄O₁₁.

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K₃V₅O₁₄,Rb₃V₅O₁₄ Tl₃V₅O₁₄ 20– 1000 . K₃V₅O₁₄ . Tl₃V₅O₁₄ 360, TlVO₃ Tl₂V₆O₁₆. Rb₃V₅O₁₄ 300, RbVO₃ Rb₂V₆O₁₆. RbVO₃ Rb₂V₄O₁₁.

     

Thermal properties of complexes

Complexes of saponified polyacrylonitrile with the bivalent metals Ca, Co, Cu, Mg, Ni and Zn, were obtained. Thermal analysis of the complexes was carried out. The highest thermal stability was found for the complexes with Co and Ni.     

Thermal properties of hydrofluorides

Data are presented on the properties of alkali metal and alkaline earth hydrofluorides. Melting, thermal decomposition and interaction of hydrofluorides with various classes of inorganic substances are discussed. Some regularities of changes in thermal properties within the sequences of the above hydrofluorides are established. Future directions of research in this field are outlined.

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Zusammenfassung Angaben über die thermischen Eigenschaften von Alkali und Erdalkali-hydrofluoriden werden bekanntgegeben. Schmelzen, thermische Zersetzung und Reaktion von Hydrofluoriden mit verschiedenen Gruppen anorganischer Substanzen werden erörtert. Einige Regelmäßigkeiten der Änderungen der thermischen Eigenschaften innerhalb der Sequenzen obiger Hydrofluoride werden festgestellt. Umrisse der zukünftigen Richtlinien für die Forschungsarbeit auf diesem Gebiete werden gegeben.

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Résumé On présente les données se rapportant aux propriétés thermiques des hydrofluorures des métaux alcalins et alcalino-terreux. La fusion, la décomposition thermique et l'interaction des hydrofluorures avec différents groupes de substances inorganiques sont discutées. On montre qu'il existe une certaine régularité dans l'évolution des propriétés thermiques à l'intérieur de la séquence des hydrofluorures mentionnés ci-dessus. On présente la direction future des recherches dans ce domaine.

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Thermal rearrangements of some indole alkaloid derivatives

Under both static and flow thermolysis conditions, several compounds with an “aspidosperma” framework rearranged to “vinca” derivatives. Thus (-)1,2-dehydroaspidospermidine ($\text{4}$) rearranged to (-) gave vincane $\text{14}$. Compound $\text{6}$ rearranged to vincamine ($\text{13a}$) and 16-epi vincamine ($\text{13b}$) under either condition ; increasing the temperature resulted in formation of apovincamine ($\text{19}$) (pyrolysis) or vincamone thermolysis).     

Thermal behaviour of complexes of antipyrine derivatives II

Parent and mixed ligand complexes of cobalt(II) and copper(II) ions with N,N-bis-(4-antipyrylmethyl)piperazine or N,N-tetra(4-antipyryl-methyl)-1,2-diaminoethane or/and imidazole as ligand and ClO ₄ ^– or SCN^– as counterion were synthesised and their thermal behaviour was investigated.This work was performed in the framework of cooperation between the Hungarian Academy of Sciences and Romanian Academy and was supported financially, in part, by the Hungarian Scientific Research Foundation (OTKA T 029554).     

Thermodynamic properties of anthraquinone derivatives

The enthalpies of solution of a series of anthraquinone derivatives in dioxane at various dilutions were determined by isothermal calorimetry.     

Sorption properties of adamantane derivatives

The chromatographic behavior of adamantane derivatives as sorbates and sorbents was studied. The retention characteristics of adamantane derivatives and some organic compounds on an adamantylsilicone stationary phase were determined. The effect of various substituents on the chromatographic behavior of the compounds was examined. Correlations between the sorption and structural characteristics of adamantane derivatives were found.     

Antiknock properties of furfural derivatives

Preparative amounts of furfuryl alcohol ethers and furfural acetals were prepared from renewable vegetable raw materials. The blending reseach octane numbers of mixing of furan derivatives in straight-run gasoline were estimated: butyl furfuryl ether, 97.8 ± 7; propyl furfuryl ether, 112 ± 6; furfural diethyl acetal, 105 ± 6, furfural ethylene glycol acetal, 108 ± 7; furfurylamine, 194 ± 4. These results demonstrate prospects for using furan derivatives as available biofuels.     

Thermal decomposition of haemin chloride and related derivatives

Differential scanning calorimetry was used to study the thermal decomposition of haemin chloride and its derivatives protoporphyrin and bilirubin. Under a static air atmosphere, exothermic transitions due to degradation were recorded for the two former compounds, whereas bilirubin exhibited a higher thermal stability. Thermogravimetry indicated that the weight loss process with these compounds under an oxidizing atmosphere of oxygen was different from that under an inert atmosphere of nitrogen. Infrared spectra of these compounds were also recorded and are briefly discussed.     

Thermal stability of ferrocene derivatives and ferrocene-containing polyamides

Thermogravimetric data and the kinetic interpretation of the curves of mass loss for ferrocene, ferrocenecarboxylic and ferrocenedicarboxylic acids and a series of ferrocene-containing polyamides are presented. The results indicate that the degradation process occurred with more than one stage of thermal degradation. The apparent activation energy values and the FTIR spectra of the degradation products suggest that the degradation mechanism occurred by either scission of weak links or by random scission of the chain. Apparently, the N-vicinal methylene group was the primary site of attack of oxygen on the polymer chain. This revised version was published online in August 2006 with corrections to the Cover Date.