Gasphasen-Reaktionen. 92. Thermische HCl-Abspaltung aus Alkyldichlorphosphanen (H3C/H)3C?PCl2 zu Phosphaalkenen (H3C/H)2CPCl und Phosphaalkinen (H3C/H)C≡P

Gasphase Reactions. 92 Thermal Elimination of HCl from Alkyldichlorophosphanes (H₃C/H)₃C? PCl₂ to Phosphaalkenes (H₃C/H)₂C?PCl and Phosphaalkines (H₃C/H)C≡P The alkyldichlorophosphanes H₃C? PCl₂, ClH₂? PCl₂, (H₃C)H₂C? PCl₂ and (H₃C)₂HC? PCl₂ split off HCl on heating in a gasflow under reduced pressure. PE spectroscopic gas analysis proves that under these conditions the short-lived phosphaalkenes H₂C?PCl, (H₃C)H₂C?PCl and – catalyzed by [MgCl₂? MgO/SiO₂]_∞ – (H₃C)₂C?PCl as well as the phosphaalkines HC≡P and (H₃C)C≡P are formed, all of which can be isolated by low temperature condensation. Based on the PES ionization patterns recorded and on the MNDO calculations for their assignment, the π_CP multiple bonds are discussed. The presumable pathway of the HCl elimination is rationalized for (H₃C)H₂C? PCl₂ by an approximate MNDO energy hypersurface.     

Thermal and photoluminescence properties of hydrated YPO4:Eu nanowires

In this work, we used the solution precipitation route to synthesize Eu³⁺-doped YPO₄·nH₂O nanowires. The structure, morphology, composition, thermal behavior, and photoluminescence of as-synthesized product were characterized by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopic (FE-SEM) and photoluminescence (PL) spectra. The dependence of the structure, morphology, composition and luminescent properties on the thermal treatment was investigated. The results indicate that the aqueous synthesis has a better control on the structure, morphology, composition of the products, and that the heat treatment induces the transitions of the structure, composition, and luminescent properties.     

Thermal characterization and thermal degradation of poly(norbornene-2,3-dicarboxylic acid dialkyl esters) synthesized by vinyl addition polymerization

The thermal properties and degradation behaviors of poly(norbornene-2,3-dicarboxylic acid dialkyl esters) (PNB-dialkyl esters) (alkyl = Me (PNB-Me), Et (PNB-Et), Pr (PNB-Pr), and Bu (PNB-Bu)) were investigated by thermogravimetric analysis (TGA) in dynamic conditions and by infrared (IR) spectroscopy. The PNB-dialkyl esters show good thermal stability up to 350 °C, and the thermal stability decreases in the order Me > Et > Pr > Bu with the increase in size of side chain. The effect of side-chain size on the thermal degradation behaviors of PNB-dialkyl esters is evidenced by one-step thermal degradation profile for PNB-Me while two-step thermal degradation profile for PNB-Et, PNB-Pr, and PNB-Bu. Transformation is deduced to undergo β-hydrogen elimination and formation of anhydride group in the first stage of thermal degradation reaction according to TGA and IR results for PNB-Et, PNB-Pr, and PNB-Bu. The apparent activation energy and thermal degradation model of PNB-dialkyl esters are estimated by means of Ozawa-Flynn-wall method and Phadnis-Deshpande method, respectively.     

The effect of (natural) polyols on the initial colour of heavy metal- and zinc-free poly(vinyl chloride)

The propensity of (natural) polyols dispersed in heavy metal- and zinc-free PVC sheets to improve the initial colour, e.g. the colour during the first minutes of exposure to high processing temperatures (short-term stability), has been investigated. It is shown using W(Lab) values that the initial colour improves upon addition of polyols containing primary hydroxyl groups. The polyols act as HCl scavengers, presumably via an acid-catalysed S_N2 substitution of the primary hydroxyl groups by chloride ions. In contrast, polyols with only secondary or tertiary hydroxyl groups accelerate the thermal degradation of PVC. Notwithstanding, the efficacy of the (natural) polyols containing primary hydroxyl groups will be reduced if the polyol is susceptible to competitive acid-catalysed intramolecular cyclodehydration reactions under the processing conditions. This is substantiated by a comparison of the behaviour of mannitol and 3,4-di-O-methyl-d-mannitol. The methylated derivative, which is less prone to undergo intramolecular cyclodehydration, improves the initial colour of heavy metal- and zinc-free PVC sheets more significantly than mannitol itself.     

Thermal behaviour of amorphous Li2ZrO3 prepared by sol-gel technique

The results of the investigations of thermal behaviour of Li₂ZrO₃, prepared in the amorphous state by means of sol-gel technique are demonstrated. The thermal treatment was carried out in air under constant heating rate of 5 deg·min^–1 and cooling rate of 2.5 deg·min^–1. The methods of DTA, TG, Emanation Thermal Analysis (ETA) and dilatometry were used, for characterization of the thermal behaviour in dynamic conditions. The X-ray diffraction patterns were used for characterization of the phase changes observed by TA Methods.

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Zusammenfassung Ergebnisse aus Untersuchungen des thermischen Verhaltens von Li₂ZrO₃, hergestellt mittels einer Sol-Gel-Technik im amorphen Zustand werden dargelegt. Die thermische Behandlung wurde in Luft bei einer konstanten Aufheizgeschwindigkeit von 5 Grad·min^–1 und einer Abkühlgeschwindigkeit von 2,5Grad·min^–1 durchgeführt. Zur Beschreibung des thermischen Verhaltens unter dynamischen Verhältnissen wurden DTA, TG, Emanationsthermoanalyse und Dilatometrie angewendet. Zur näheren Charakterisierung der bei TG beobachteten Phasenumwandlungen wurde Röntgendiffraktion verwendet.

     

p-CH3C6H4SR型硫醚与钯(II)配合物热分解反应动力学

热重分析(TG)和微商热重法(DTG)广泛应用于各个研究领域,用非等温热重法测定固体化合物的热分解动力学参数已有报导.许多作者提出各种不同的数据处理方法.本文用的ρ-CH_3C_6H_4SR 型硫醚对钯的萃取具有选择性好、分配比高、气味较小、易溶于脂肪烃类溶剂、易于合成、是很有发展前途的一类萃取剂.我们合成五种ρ-CH_3C_6H_4SR(R:n-C_4H_9,n-C_6H_(13),n-C_8H_(17),n-C_(10)H_(21),n-C_(12)H_(25))型硫醚与钯(Ⅱ)的配合物,用TG-DTG 法研究它们的热分解过程,用微商法(Freeman-Carroll 方程)及积分法(Coats-Redfern 方程)获得了这些配合物的热分解动力学参数.     

Thermal conductivity of the urea-hexadecane inclusion compound

The thermal conductivity and the heat capacity per unit volumec _p have been measured for the urea-hexadecane inclusion compound using the transient hot-wire method. Measurements were made under isobaric conditions at a pressure of 0.1 GPa and in the temperature range of 100–300 K. There was evidence for a phase transition at a temperature of about 160 K, in reasonable agreement with previous work. For the high-temperature phase was independent of temperature within ±1%. The low-temperature phase showed a weak temperature dependence, with (d In/d InT) _p = –0.13. It was inferred that interaction between acoustic phonons and low-frequency vibrational excitations of the guest molecules made a major contribution to the thermal resistivity. For the quantityc _p a weak maximum was observed in the region of the phase transition temperature.Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena.     

含二苯甲烷结构四元共缩聚杂萘聚芳酰胺的合成与性能

采用自制二胺1,2-二氢-2-(4-氨基苯基)-4-[4-(4-氨基苯氧基)-苯基]-二氮杂萘-1-酮、商品二胺4,4′-二氨基二苯甲烷和对苯二胺与对苯二甲酰氯进行低温溶液缩聚反应,改变三种二胺的比例,得到了一系列共聚酰胺树脂,其特性粘数为1·24~2·32dL/g,用FT-IR、1H-NMR手段研究了聚合物的结构;利用DSC和TGA研究了聚合物的耐热性能,结果表明,该类聚合物具有较高玻璃转化温度(301℃以上);氮气气氛中5%热失重温度在438℃以上;用一定比例的二胺制得的聚合物分别能溶于N-甲基吡咯烷酮、N,N-二甲基乙酰胺等非质子极性溶剂中并浇注得到韧性薄膜.     

The reciprocal CuInS2+2CdSe⇔CuInSe2+2CdS system. Part I. The quasi-binary CuInSe2-CdSe system: Phase diagram and crystal structure of solid solutions

The type of interaction in quasi-binary system CuInSe₂ (CIS)-CdSe was investigated using differential thermal and X-ray phase analysis methods. The limits of existence of solid solutions based on low-temperature (α) and high-temperature (γ) CIS modifications and CdSe (β) with chalcopyrite, sphalerite and wurtzite structures, respectively, were established in sub-solidus region at 620 K and 870 K. For certain compositions of solid solutions, the structure was refined using powder X-ray diffraction. A phase diagram of the CIS-CdSe system was constructed. A peritectic process L+β⇔γ takes place in the system at 1260 K.     

Concerning the Thermal Diastereomerization of the Green Fluorescent Protein Chromophore

Summary. Two model compounds for the green fluorescent protein chromophore were prepared. One of them incorporates the natural 4-hydroxybenzylidene group of the natural tyrosin derived chromophore, the other one bears a methyl group instead of the hydroxy group. Whereas the photochemically prepared (E)-diastereomer of the first compound very effectively reverted thermally (room temperature) to the thermodynamically stable (Z)-diastereomer, the (E)-diastereomer of the second derivative proved to be stable even at elevated temperatures for more than a day. This finding can be rationalized by constructing the appropriate resonance structures showing that only in the first case an effective delocalization enables partial single bond character of the benzylidene double bond. From the standpoint of chemical etiology, only Nature’s choice of the tyrosin derived chromophore of the green fluorescent protein provides an efficient radiationless thermal relaxation channel for the unwanted photo-diastereomerization product formed after excitation besides the dominating fluorescence channel of its chromophore.