n-Butyllithium/α-methylstyrene/benzene/diethyl ether: A suitable initiation system for anionic syntheses of model co- and homopolymers of styrene and isoprene

An initiation system of the anionic polymerization, intended for the syntheses of homopolymers and block copolymers with narrow molar mass distribution, was tested with styrene and isoprene. The actual initiating species, viz., the oligomeric α-methylstyryl anion, originates by the reaction of n-butyllithium with α-methylstyrene in a benzene/diethyl ether 1:1 (v:v) solvent mixture at room temperature. The homopolymers and two-block copolymers of styrene and isoprene, prepared by using this system, were characterized by light scattering, membrance osmometry, GPC, and ¹H NMR spectroscopy. By using the suggested initiation system, it is possible to synthesize well-defined homopolymers and block copolymers with low polydispersity (as judged by the shape of the GPC peaks and by the values of the polydispersity index), especially in a molar mass region between 4 × 10⁴ and 1.5 × 10⁵ g/mol. Above the upper limit of this interval, an appropriate decrease of the diethyl ether/benzene volume ratio is recommended, though the polymerization time must then be prolonged.     

Strukturelle Untersuchungen einiger neutraler Komplexe des zweiwertigen Molybdäns

Unit cell parameters have been calculated from x-ray powder diffraction data of Mo₂Br₄ Py ₄ (A), Mo₂I₄ Py ₄ (B), Mo₂I₄ Pic ₄ (C), Mo₂(SCN)₄ Py ₄ (D) and Mo₂(SCN)₄ Pic ₄ (E), A, B and C crystallize tetragonal. A witha=9,4₂,c=15,O₂ Å; B witha=9,4₆,c=14,9₈ Å and C witha=9,6₆ andc=15,7₂ Å D and E crystallize orthorhombic. D witha=10,0₉,b=9,1₄,c=15,0₈ Å; E witha=10,2₂,b=9,4₁ andc=15,1₅ Å.Py=pyridine,Pic=4-methylpyridine.

     

Forms of vibrations and structural changes in liquid state

Summary The forms of vibrations and displacements of particles in amorphous structures have been investigated. The particles, moving on highly non-linear amplitude, are responsible for the creation of disordered structures of amorphous bodies. The non-linear oscillators, even if 'few' in concentration, are characterized by unpredictable trajectories in phase space. The non-linear oscillators are fully developed in the liquid state above the crossover temperature T_cr and between T_cr and T_g their number decreases. Under T_g they completely disappear. The interconnection between the linear oscillators in blocks plays the most important role in the characteristic time spectra in liquid state. Using the additive properties of elements polarizibilities, the number of acoustical units in individual blocks at T_cr is estimated to be about 600 units. The diameter of blocks at T_cr was estimated to be about 1.8 nm. Even if the non-linear high amplitude motions disappear at solidification, the remnants of structural irregularity remain and the disordered structure of glass is formed.     

A new phase in the Ag−O−S system

The investigations of reaction between Ag₂SO₄ and Ag₂S in air atmosphere have been carried. Results of DTA and X-ray phase powder diffraction of a reaction mixture have confirmed that in the Ag?O?S system exists a new phase. A formula of the phase is Ag₂SO₂.     

Study of isotope exchange reactions by double labelling

This paper presents the method of double labelling in the study of the kinetics of homogeneous isotope exchange reactions. This method was tested by the determination of the Sn(II)−Sn(IV) exchange rate in hydrochloric acid medium. The system was labelled by the tracer^119mSn [initially in the Sn(IV) state]; when the isotope equilibrium was established, Sn(IV) was again labelled by tracer¹¹³Sn. The separation of Sn(II) and Sn(IV) in the given time of exchange was performed by the extraction of Sn(IV)-hydroxyquinolate into chloroform. The specific activities of the separated components were determined from the ratio of¹¹³Sn and^119mSn activities. The exchange rate was calculated from the time dependence of specific activities. The advantage and possibilities of the method of double labelling in the study of isotope exchange are discussed.     

Preparation and thermal decomposition of halogenometallates

Five new derivatives of general formula [Ru(dipy)₃]MCl₄, whereM=Cu(II), Zn(II), Mn(II), Fe(II) and Co(II), and [Ru(dipy)₃][FeCl₄]₂ were synthesized, and their compositions and structures were confirmed by chemical analysis and electron absorptionüspectroscopy. The thermal decompositions of the compounds were studied by thermoanalytical methods. All these complexes decompose upon heating up to 1300 K, with simultaneous loss of organic fragments and structures were confirmed by chemical analysis and electron absorption spectroscopy.The exothermic effects. The residues after heating correspond to RuO₂ and the appropriate M oxides, contaminated in some cases by pure metal.

---

Zusammenfassung Fünf neue Komplexverbindungen des Typs [Ru(dipy)₃](MCl₄] (dipy=2,2-Dipyridyl;M=Cu, Zn, Mn, Fe, Co) sowie [Ru(dipy₃](FeCl₄]₂ wurden dargestellt und ihre Zusammensetzung und Struktur durch chemische Analyse und Elektronenspektroskopie bestätigt. Ihre thermische Zersetzung wurde durch simultane TG-DTA untersucht. Alle Komplexverbindungen zersetzen sich beim Erhitzen bis auf 1300 K unter gleichzeitigem Verlust der organischen Komponente und des Cl an die Gasphase. Der thermische Abbau ist von starken exothermen Effekten begleitet. Die Rückstände nach dem Erhitzen enthalten RuO₂ und das jeweilige Metalloxid, in einigen Fällen durch Metall verunreinigt.

---

[Ru(dipy)₃]MCl₄, M = , , , , [Ru(dipy)₃][FeCl₄]₂. , . 1300 . . , .

     

Thermal decompositions of light lanthanide aconitates

The conditions of thermal decomposition of Y, La, Ce(III), Pr, Nd, Sm, and Gd aconitates have been studied. On heating, the aconitate of Ce(III) loses crystallization water to yield anhydrous salt, which then is transformed in to oxide CeO₂. The aconitates of Y, Pr, Nd, Sm, Eu and Gd decompose in three stages. First, aconitates undergo dehydration to form the anhydrous salts, which next decompose to Ln₂O₂CO₃. In the last one the thermal decomposition of Ln₂O₂CO₃ to Ln₂O₃ is accompanied by endothermic effect. Dehydration of aconitate of La undergoes in two stages. The anhydrous complex decomposes to La₂O₂CO₃; this subsequently decomposes to La₂O₃.     

On distribution of molecular weight in anionic polymerizates of caprolactam

Measurement has been made of the dependence of the molecular weight distribution on the ratio of the catalytic system components and on the polymerization time for polycaprolactam obtained by anionic polymerization. A bimodal character of the curves was observed for products made using molar ratios of activator (N-benzoylcaprolactam) to initiator (sodium dihydro-bis(methoxyethoxy)aluminate) of 1:1 and 1:3, when the polymerization times were less than 1 hr. This course is explained by the influence of fast side-reactions, mainly condensations. For a ratio of 3:1 of the components of the catalytic system, smooth integral distribution curves are obtained, accounting for a very fast decrease in the strong base concentration in the initial stages of the polymerization.     

Solubility Study of Nimodipine Inclusion Complexation with α- and β-Cyclodextrin and some Substituted Cyclodextrins

The solubility of nimodipine was measured in aqueous solutions of the following cyclodextrins: -cyclodextrin (-CD), hydroxypropyl--CD (HP--CD), -cyclodextrin (-CD), random substituted methyl--CD (M--CD), three hydroxypropyl--CDs (HP--CD) with mutually different average degree of substitution, and hydroxypropyl--cyclodextrin (HP--CD). From the determined linear solubility diagrams the values of the binding constant K₁₁ of the inclusion complexes of nimodipine with the respective CDs were evaluated. The -CDs efficiently solubilized sparingly soluble nimodipine, the highest value of K₁₁ was found for M--CD (1680 M^-1), followed by -CD (550 M^-1) and HP--CDs, where the higher degree of substitution lowered K₁₁. Only slight solubilization of nimodipine was observed in the solutions of the -CDs and HP--CD.     

Application of High Pressure-DTA for High Pressure-liquid Phase Epitaxy of Doped Mercury and Thallium HTS Formations

The fabrication method of superconducting thin films of compositions HgBa₂Ca₂Cu₃O_8+δ (Hg-1223) and Tl₂Ba₂CuO_y (2201) on single-crystalline SrTiO₃ and LaAlO₃ substrates is reported. The highest obtained T _c was 134 K and J _c over 10⁶ A cm^–2 at 77 K. High pressure DTA(HP-DTA) was applied to grow mercury- and thallium-based high-temperature superconducting crystals and thin films, to identify melting points of particular phases within these oxide systems and determine suitable processing conditions. The DTA system operates at the: maximum temperature of 1200°C, volume up to 5 cm³, working pressure up to 1.5 GPa and at a working atmosphere — inert gas with up to 25% oxygen. This revised version was published online in August 2006 with corrections to the Cover Date.