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1

VO2(B) conversion to VO2(A) and VO2(M) and their oxidation resistance and optical switching properties

Zhang Y.

Materials Science Poland

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2016

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Vol. 34, No. 1

169--176

EN

Vanadium dioxide VO2 has been paid in recent years increasing attention because of its various applications, however, its oxidation resistance properties in air atmosphere have rarely been reported. Herein, VO2 (B) nanobelts were transformed into VO2 (A) and VO2 (M) nanobelts by hydrothermal route and calcination treatment, respectively. Then, we comparatively studied the oxidation resistance properties of VO2 (B), VO2 (A) and VO2 (M) nanobelts in air atmosphere by thermo-gravimetric analysis and differential thermal analysis (TGA/DTA). It was found that the nanobelts had good thermal stability and oxidation resistance below 341 degrees C, 408 degrees C and 465 degrees C in air, respectively, indicating that they were stable in air at room temperature. The fierce oxidation of the nanobelts occurred at 426, 507 and 645 degrees C, respectively. The results showed that the VO2 (M) nanobelts had the best thermal stability and oxidation resistance among the others. Furthermore, the phase transition temperatures and optical switching properties of VO2 (A) and VO2 (M) were studied by differential scanning calorimetry (DSC) and variable-temperature infrared spectra. It was found that the VO2 (A) and VO2 (M) nanobelts had outstanding thermochromic character and optical switching properties.

2

Quantitative analysis of α-CL-20 polymorphic impurity in ε-CL-20 using Dispersive Raman Spectroscopy

Ghosh M., Venkatesan V., Sikder N., Sikder A. K.

Central European Journal of Energetic Materials

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2013

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Vol. 10, no. 3

419--438

EN

α-CL-20 polymorphic impurity in ε-CL-20 studies have been carried out using Dispersive Raman Spectroscopy. ε-, β-, α- and γ-CL-20 polymorphs were produced using crystallization methods with sample recovery from the solution being >90%, and chemical purity of about 99%. The polymorphs prepared were characterized using Dispersive Raman Spectroscopy over the Raman shift region of 100-3500 cm-1 using a 514 nm argon ion laser. The experimental studies were supported by ab initio computations performed at B3LYP level using a 6-31+G** basis set. The computed vibrational frequencies of the CL-20 conformers correspond to the ε, β and α or γ-CL-20 polymorphs when compared with the observed frequencies. α-CL-20 shows a distinct feature at 280 cm-1 as compared with those of the ε-CL-20 polymorph. Using Dispersive Raman Spectroscopy, a linear relationship was demonstrated for the absolute peak height and absolute peak area ratio of α-CL-20 versus the weight percent of α-CL-20. This method enables a detection limit of this polymorphic impurity down to 2 wt%.

3

The Influence of Processing Parameters on the Supermolecular Structure of Isotactic Polypropylene in PP/LDPE Blends

Borysiak S.

Fibres & Textiles in Eastern Europe

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2008

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Vol. 16, no. 6 (71)

93--96

EN

In order to analyse the effect of the addition of low-density polyethylene (LD-PE) on the polymorphic transformation in isotactic polypropylene (iPP), structure studies of iPP/LDPE blends have been carried out. In this work, iPP/LD-PE blends (100/0, 90/10, 80/20 and 70/30 w/w) were prepared by injection moulding under various injection speeds. The supermolecular structure of the blends by means of wide-angle X-ray scattering (WAXS) was analysed. The results have shown that polymorphs of polypropylene developed due to melt-shearing in the mould strongly depend on the injection speed as well as the content of LD-PE in the blends. The polypropylene (without the PE component) was characterized by the highest amount of the hexagonal form. The addition of polyethylene to iPP importantly depressed the formation of β-iPP. Moreover, an increase in the amount of polyethylene caused a significant decrease in the content of the hexagonal phase of polypropylene. The polymorphs of the polypropylene matrix strongly depend on the technological parameters of the processing. At a higher speed of injection, the amount of the hexagonal form of polypropylene slightly increases.

PL

Analizowano wpływ dodatku PE niskiej gęstości (LDPE) na zmiany polimorficzne izotaktycznego PP (iPP). Mieszaniny iPP/LDPE (100/0, 90/10, 80/20 oraz 70/30% wag.) zostały przygotowane przez wtryskiwanie z różną prędkością. Struktura nadcząsteczkowa mieszanin była badana z zastosowaniem WAXS. Wyniki wskazują, że zawartość odpowiednich struktur polimorficznych PP znacząco zależy od prędkości wtryskiwania oraz zawartości PE w mieszaninie. Największą zawartością formy heksagonalnej charakteryzował się PP bez dodatku PELD. Obecność PE w matrycy iPP powoduje istotne obniżenie zawartości tej odmiany polimorficznej. Ponadto, polimorfizm PP zależy również od parametrów przetwarzania. Przy wyższych prędkościach wtryskiwania zaobserwowano zwiększenie zawartości fazy heksagonalnej PP.

4

Mesylan imatinibu : metody syntezy i otrzymywanie form polimorficznych

Szczepek W.J.

Przemysł Chemiczny

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2006

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T. 85, nr 5

306-309

PL

Przedstawiono przegląd prac badawczych dotyczących metod syntezy imatinibu oraz metod syntezy soli addycyjnych imatinibu z kwasami, z uwzględnieniem aspektu polimorfizmu mesylanu imatinibu. Opisano krótko przebieg prac nad syntezą mesylanu imatinibu i jego polimorfizmem wykonanych w Instytucie Farmaceutycznym.

EN

A review with 52 refs. covering syntheses of 4-(4-methylpiperazin-1-ylmethyl)-N-{4-methyl-3-[4-(pyridin-3-yl)pyrimidyn-2ylamino]phenyl}benzamide (imatinib) and its polymorphism, prepn. of salt adducts, and particularly the 6-step synthesis of imatinib mesylate and its α-polymorph as developed at the Pharmaceutical Research Inst. (Warsaw).

5

The Role of Hydrogen Bonds in the Pressure-Induced structural Distortion of 4-Hydroxyacetanilide Crystals

Boldyreva E., Shakhtshneider T. P., Ahsbabs H., Uchtmann H., Burgina E. B., Baltakhinov V. P.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 9

1333-1346

EN

Results of X-ray diffraction and IR-specroscopy studies of the role of hydrogen bonds in the structural distortion of the monoclinic and the orthorhombic polymorphs of paracetamol induced by hydrostatic pressure (up to 4-5 GPa) are analyzed. Two groups of phenomena were studied: (i) the anisotropic structural distortion of the same polymorph, (ii) transitions between the polymorphs induced by pressure. The bulk compressibilities of the two polymorphs are practically equal. The anisotropy of pressure-induced structural distortion is qualitatively different. Lattice expansion in particular crystallographic directions was observed for the monoclinic polymorph. With increasing pressure the intermolecular NH...O and OH...O hydrogen bonds contracted and the intramolecular angles between the planes of the phenyl ring and the acetamide group decreased. Pressure- induced transitions between the polymorphs were poorly reproducible and limited by nucleation of the new polymorph.