Stereospecific polymerization of isobutyl vinyl ether by AlR3–VCln catalysts. I. Influence of preparative conditions of the catalysts

The polymerization of isobutyl vinyl ether by the VCl_n–AIR₃ system was carefully studied. The vanadium components were prepared by the reaction between VCl₄ and AlEt₃ or n-BuLi as a reducing agent. VCl₃·LiCl and VCl₂·2LiCl are the effective catalysts for the stereospecific polymerization of isobutyl vinyl ether. When VCl₃·LiCl is combined with AlR₃, a new catalytic system is formed. The effect of the preparative conditions of the various vanadium component in the AlR₃–VCl_n system shows that the effective vanadium component is trivalent. In the polymerization by VCl₃·LiCl–Al (i-Bu)₃ system, a change of the polymerization mechanism may occur at Al(i-Bu)₃/VCl₃·LiCl ratio at around 5. When the ratio is lower than 5, a cationic polymerization by VCl₃·LiCl takes place predominantly, while at ratios higher than 5, it is suggested that the polymerization proceeds by means of a VCl₃·LiClA–Al(i-Bu)₃ complex by a coordinated anionic mechanism. The polymers obtained by these catalysts are highly crystalline. Styrene was also polymerized by using the same catalysts. VCl₃·LiCl and VCl₃·LiCl–THF complex yielded amorphous polymer by cationic polymerization. When VCl₃·LiCl was combined with 6 mole-eq of Al(i-Bu)₃, the resulting polystyrene was highly crystalline and had an isotactic structure, while the VCl₂·2LiCl–Al(i-Bu)₃ (1:6) system yielded traces of polymer of extremely low stereoregularity. The results indicate that the effective vanadium component at Al/V ≧ 6 is trivalent and that the mechanism is a coordinated anionic one.     

Stereospecific polymerization of methacrylonitrile. III. Some new catalysts for isotactic polymethacrylonitrile

Some classes of organometallic catalysts what induce stereospecific polymerization of methacrylonitrile have been found. They include organolithium aluminum compounds of the type LiAlR₄, Li[R₃AlOAlR₂], and Li[R₃AlN(R)AlR₂], organosodium aluminum compounds of the type NaAlR₄, organolithium zinc compounds of the type LiZnR₃ and Li₂ZnR₄, organomagnesium aluminum compounds of the type RMg[AlR₄] and Mg[AlR₄]₂, and organomagnesium compounds containing an Mg? N bond, such as and their related compounds. One of the features of the polymerization with these catalysts was that the crystalline polymers were formed at moderately high temperatures. Total conversion, solubility index, and molecular weight of the polymer increased with increasing polymerization temperature, as observed in the case of polymerization with diethylmagnesium catalyst. Catalysts with an Mg? N bond were found to be highly effective for the stereospecific polymerization. The acetone-insoluble fractions of the polymers gave x-ray diagrams identical to the crystalline polymer produced with diethylmagnesium. This indicates that the acetone-insoluble crystalline polymers produced with these catalysts have an isotactic structure. The viscosity–molecular weight relationship for crystalline polymer was conveniently determined in Cl₂CHCOOH at 30°C.; [η] = 2.27 × 10^?4 M^0.754.     

Zur Verwendung von Phosphors?ureanhydrid

Ohne Zusammenfassung     

Einfluß interstitiellen Wasserstoffs auf Magnetismus und Gitterkonstante ferromagnetischer NiCr-Legierungen

Measurements of magnetization, X-ray studies and volumetric investigations show that ferromagnetic nickel-chrome alloys (2 to 7% Cr) absorb hydrogen in high concentrations (β-phase). Caused by the interstitial hydrogen atoms NiCr looses its ferromagnetism, combined with reversibly enlarged lattice constants of some percent (decreasing with increasing Cr-content). The variation of lattice expansionΔ a with Cr-content is in some way similar to the recently found proportionality ofΔ a with the mean magnetic moment in the case of NiCu and NiCu-hydrogen-alloys but deviating in a characteristic manner. — X-ray studies also showed an additional increase ofΔ a by supersaturation of the β-phase, and the occurrance of a second phase with very low values ofΔ a.     

Shear-strain contours from moiré interferometry

Whole-field contour maps of shear strains _xy are derived from displacement fields obtained by moiré interferometry with 2400 /mm (60,960 /in.). Cross-derivatives of displacements are obtained by mechanical differentiation. They are summed by graphical additive moiré. The high sensitivity of moiré interferometry permits quantitative analysis in the small-strain domain.Paper was presented at V International Congress on Experimental Mechanics held in Montreal, Quebec, Canada on June 10–15, 1984.     

Carbonyl Compounds Containing Formaldehyde Produced from the Heated Mouthpiece of Tobacco Sticks for Heated Tobacco Products

Diverse harmful compounds can be emitted during the heating of tobacco sticks for heated tobacco products (HTPs). In this study, the generation of harmful compounds from the filter, instead of tobacco in tobacco sticks, was confirmed. The heat of a heated tobacco product device can be transferred to the tobacco stick filter, resulting in the generation of harmful compounds from the heated filter. Since the heating materials (tobacco consumable) of the tobacco sticks evaluated in this study were different depending on the brand, the harmful compounds emitted from the heated tobacco stick filters were examined by focusing on the carbonyl compounds, using three different tobacco stick parts. Acetaldehyde and propionaldehyde exhibited the highest concentrations in HTP aerosols produced by heating the tobacco consumable (conventional case) (63.5 ± 18.4 µg/stick and 1.71 ± 0.123 µg/stick, respectively). The aerosols produced by heating tobacco stick filters had higher formaldehyde and acrolein concentrations (0.945 ± 0.214 µg/stick and 0.519 ± 0.379 µg/stick) than the aerosols generated from heated tobacco consumable (0.641 ± 0.092 µg/stick and 0.220 ± 0.102 µg/stick). As such, formaldehyde and acrolein were produced by heating small parts of the mouthpiece of a tobacco stick, regardless of the heated tobacco product brand. In addition, acetone was only detected in the aerosols generated from heated filters (0.580 ± 0.305 µg/stick). Thus, safety evaluations of heated tobacco products should include considerations of the harmful compounds generated by heating tobacco stick mouthpieces for heated tobacco products in addition to those found in heated tobacco product aerosols.