A novel scheme of heterogeneous polymerization of ethylene

The heterogeneous polymerization of ethylene initiated by radiation in tert-butyl alcohol was studied. The polymerization was carried out in a 100-ml reactor at 25–100°C and pressures of 200–300 kg/cm² in the presence of 50 ml of tert-butyl alcohol containing 7 wt-% water. The amounts of polymerized monomer, the average molecular weight of polymer formed, and the molecular weight distribution of polymer were measured at various stages of reaction and at various temperatures. The molecular weight distribution was found to be very much dependent on the reaction time and temperature. For the polymer formed at 50–60°C in the very early stages of reaction, the molecular weight distribution is unimodal, and in the intermediate stage a shoulder appears at a molecular weight higher than the first peak which increases as the polymerization proceeds; eventually a bimodal curve is formed. The bimodal distribution curves were analyzed to determine the fractions and average molecular weights of the each peak. On the basis of these data for the molecular weight distribution and kinetic behavior, a new scheme for the heterogeneous polymerization is proposed which indicates that the polymerization proceeds via propagating radicals in two different physical states, namely, loose and rigid states.     

Thermally stable rigid π-allylnickel compounds, (π-CHRCR′CR2)Ni(PPhMe2)C6Cl5

The reaction of C₆Cl₅Ni(PPhMe₂)₂Cl with CHRCR′CH₂MgX (X = Br or Cl) yields π-allylnickel compounds, (π-CHRCR′CH₂)Ni(PPhMe₂)C₆Cl₅ (Ia, R = R′ = H; Ib, R = H, R′ = CH₃; Ic, R = CH₃, R′ = H), which are stable in the solid state below ca. 150°C and are fairly stable in solution in the absence of oxygen. The π-allyl group was found by PMR spectroscopy to be rigid even in the presence of an excess of PPhMe₂, P(OEt)₃ or P(OMe)₃.     

Relaxations of selenium in crystalline and amorphous states

Complex shear modulus at 33 kc./sec. is measured at temperatures of ?150–150°C. for amorphous selenium and crystalline selenium with different crystallinities. The dielectric relaxation at 10 kc./sec. to 3 kc./sec. to 3 Mc./sec. is observed at temperatures of ?32–25°C. for iodine-doped crystalline selenium. It is concluded from the results of this study and of others' that selenium exhibits four relaxations, α, β γ, and δ, in order of descending temperature. The β relaxation is observed only in the amorphous sample above the glass temperature and is assigned to the primary relaxation. The α, γ, and δ relaxations are found in the crystalline selenium. The α relaxation, which is prominent in a highly crystalline sample, is assigned to the crystalline relaxation. The γ and δ relaxations increase in peak height with decreasing crystallinity and are attributed to the disordered region in the crystalline selenium. The dispersion map (logarithm of frequency versus reciprocal absolute temperature of loss maximum) of selenium is presented.     

Separation and simultaneous determination of cobalt, nickel and copper with 2-(4-methyl-2-quinolylazo)-5-diethylaminophenol by reversed-phase high-performance liquid chromatography

Performance of six quinolylazo compounds was studied as a pre-column derivatizing reagent for the separation of metal ions in the reversed-phase high-performance liquid chromatography. 2-(4-Methyl-2-quinolylazo)-5-diethylaminophenol (QADP) was suited for the determination of Co, Ni and Cu in the presence of a large amount of Fe. The detection limits under the optimized conditions [stationary phase: L-column ODS; mobile phase: acetone-water (62:38, v/v) containing 0.01 M NH(4)SCN and 0.01 M 2-morpholinoethanesulfonic acid-NaOH (pH 6); injection volume: 10 mul] were 0.24 ng for Co, 0.22 for Ni and 0.53 for Cu. This method was successfully applied to the determination of these metal ions in a standard steel sample.     

Molecular design of crown ethers. 21.(1,2) synthesis of novel double-armed benzo-15-crown-5 lariats and their complexation thermodynamics with light lanthanoid nitrates in acetonitrile

Three new disubstituted benzo-15-crown-5 derivatives (3-5) have been synthesized from 4',5'-bis(bromomethyl)benzo-15-crown-5 (2) and the corresponding alkanols in the presence of Na(2)S(2), and their complexation thermodynamics with light lanthanoid(III) nitrates (La-Gd) have been studied in anhydrous acetonitrile at 25 degrees C. Plots of K(S) against the reciprocal ionic diameter of lanthanoid exhibited monotonically declining pattern for the parent benzo-15-crown-5 (1) and 3 but showed a characteristic peak at Ce(3+) for 4 and 5. It is interesting to note that the simple extension of the alkyl side chains in 4 and 5 can alter the cation selectivity profiles of 1 and 3. Possessing two 2-oxapropyl groups, 3 gave a comparable K(S) for La(3+) but a significantly decreased K(S) for Ce(3+) compared with the corresponding values for 1, thus exhibiting an exceptionally high La(3+)/Ce(3+) selectivity of 11. Thermodynamically, the complexation of lanthanoid perchlorates with 1 is absolutely entropy-driven in acetonitrile, while the complexation of lanthanoid nitrates with 3-5 is primarily driven by exothermic enthalpy changes with accompanying moderate entropic gain or small entropic loss.     

Effect of dose rate on the radiation-induced polymerization of ethylene in tert-butyl alcohol

The dependence of the dose rate on the rate of radiation-induced polymerization of ethylene in tert-butyl alcohol containing 5 vol-% water was studied. The reaction was carried out by use of a reactor with a capacity of 100 ml under the following conditions: pressure, 200 kg/cm²; temperature, 24 ± 3°C; dose rate, 3.7 × 10⁴?1.6 × 10⁵ rad/hr; amount of medium, 70 ml. The dose rate exponents for rate of the polymerization, the molecular weight, and the number of polymer chain were found to be about 0.8, ?0.1, and 0.9, respectively. These results were well explained with kinetic results (obtained by a novel analytical method) for the polymerization which contain both first-order and second-order terminations for the concentrations of propagating radical. The individual values of the rate constants in each elementary reaction were also obtained.     

Unusual Reactivities of ortho-Hydroxy-β-nitrostyrene

Nitrostyrene derivatives are widely used in organic syntheses as a substrate for Michael addition, photoisomerization and cycloaddition. In contrast, ortho-hydroxy derivatives exhibit unusual behaviors in these reactions. Conjugate addition proceeded upon treatment of the ortho-hydroxy-β-nitrostyrene with an amine; however, subsequent C–C bond cleavage readily occurred to afford the corresponding imine. Moreover, conversion of the trans-isomer to a cis-isomer did not occur efficiently, even when UV light was irradiated. We studied these unusual behaviors of β-nitrostyrene, focusing on the role of the ortho-hydroxy group.     

Umwandlung des Fe3S4 von Fd3m nach Pa3, P4/nmm bzw. P63/mmc beim hydrothermalen Prozeß

A hydrothermal process of precipitating iron sulfide gives rise to greigite (space group: Fd3m), pyrite (Pa3), mackinawite (P4/nmm) and pyrrhotite (P6/mmc), as the case may be. Greigite blended with pyrite is formed, when the autoclave for the hydrothermal process is cooled down not rapidly, but slowly from 192°C to room temperature. Greigite and pyrite here form partially a solid solution. A mechanical mixture of greigite-mackinawite and that of greigite-pyrrhotite appear in the hydrothermal process above and below 192°C, respectively. Pure greigite is produced only by rapid quenching of the reaction tube from 192°C, to 10°C.     

A precision measurement of the hyperfine structure of87Sr+

The ground state hyperfine splitting of⁸⁷Sr⁺ was measured with a precision of 1×10^–8. The experiments were performed with an RF ion trap connected to an ISOL (isotope separator on-line), where all the possible transitions between Zeeman sublevels were observed by a laser-microwave double resonance method. The magnetic dipole hyperfine constant was determined to beA=–1 000 473.673 (11) kHz.     

A new effect of ultrasonication on the formation of BaTiO3 nanoparticles

A new effect of ultrasonic irradiation on the formation of BaTiO₃ particles was identified. Ultrasonication caused the aggregation of the original 5–10 nm BaTiO₃ particles in the same crystal axis and accelerated the formation of BaTiO₃ particles significantly. Furthermore, narrow size distribution was obtained for the aggregated particles under ultrasonic irradiation.