Radiation-induced solid-state polymerization in binary systems. II. Relationship between polymerization rate and physical structure of binary systems

The radiation-induced solid-state polymerization of binary systems consisting of acrylic monomer (acrylamide, acrylic acid) and organic compounds was investigated. In the previous paper on binary systems the authors reported that the rate of polymerization increased in the solid state (eutectic mixture systems). The mechanism of rate increase has been investigated by examination of phase diagrams, viscosities, and surface tension of the binary systems. Viscosity and surface tension are the measure of the molecular interaction of the two-component systems. In addition, the effect of linear crystal growth rate and half maximum width of the x-ray diffraction diagram of the crystallization process were determined. The larger the molecular interaction between the two components, the slower the linear crystal growth rate of monomer. The size of the monomer crystal decreases and the dislocation density of the monomer crystals increases in systems with large molecular interaction. Consequently it can be concluded that the physical structure of a binary solid system is the most important parameter determining the rate increase of solid-state polymerization. Dislocation on the grain boundary is more important than defects inside of the crystal lattice. It was found that the acceleration of polymerization rate is large in binary systems with larger molecular interaction. In some systems such as organic acid—amide systems with strong hydrogen bonds, glassy phases may be formed in which monomer may readily polymerize at very low temperatures.     

A three‐dimensional CuII–WIV bimetallic porous assembly containing a zigzag ladder structure

The asymmetric unit of the three‐dimensional Cu^II–W^IV polymeric assembly {[Cu(en)₂][Cu(en)][W(CN)₈]·4H₂O}_n (en is ethyl­enedi­amine, C₂H₈N₂) or {[Cu₂W(CN)₈(C₂H₈N₂)₃]·4H₂O}_n, which can be named as polymeric bis­(ethyl­enedi­amine)copper(II) (ethyl­enedi­amine)copper(II) octa­cyano­tungstate(IV) tetrahydrate or penta‐μ‐cyano‐tri­cyano­tris­(ethyl­enedi­amine)­dicopper(II)­tungsten(IV) tetra­hydrate, consists of two half [Cu(en)₂]²⁺ cations (Cu²⁺ on inversion centres), a [Cu(en)]²⁺ cation and a [W(CN)₈]^4? ion, together with four water mol­ecules. The latter Cu^II site is coordinated by five N atoms from an en ligand and by three cyanides in a distorted square‐pyramidal geometry. The Cu^II atoms of the two [Cu(en)₂]²⁺ cations reside in an elongated octahedral coordination environment, and one of them is localized at a centre of inversion. The W atom is coordinated by eight cyano groups in an irregular square antiprism. Five of these act as bridging units connecting the W and the three Cu atoms, to form an infinite three‐dimensional porous network containing a zigzag ladder structure.     

Photoreactions of N-vinylcarbazole induced by metal salts. II. Further studies on the photocationic polymerization sensitized by sodium chloroaurate(III) in nitrobenzene

Further investigations of the photopolymerization of N-vinylcarbazole(VCZ) sensitized by sodium chloroaurate(III) in nitrobenzene were undertaken under irradiation of near-ultraviolet light at 30°C. Copolymerization with isobutyl vinyl ether and the kinetic behavior of polymerization were studied. These propagation and chain-breaking features were discussed in comparison with those obtained in the thermal polymerization. Electron spin resonance spectroscopy was conducted at 77°K in various systems.     

Helical superstructures of fullerene peapods and empty single-walled carbon nanotubes formed in water

Aqueous dispersions of fullerene C70-filled carbon nanotubes (C70@SWNTs or peapods) and empty single-walled carbon nanotubes (empty SWNTs) were prepared with the aid of trimethyl-(2-oxo-2-pyrene-1-yl-ethyl)-ammonium bromide (1), which is a carbon nanotube solubilizer. This is the first report describing the preparation and characterization of the transparent dispersion/dissolution of the peapods. The UV-vis-near-IR spectra of C70@SWNTs-1 and empty SWNTs-1 were almost identical. We found by means of transmission electron microscopy and atomic force microscopy that the empty SWNTs and C70-peapods form helical nanostructures in the shapes of rings, irregular rings, lassos, handcuffs, catenanes, pseudorotaxanes, and figure-eight structures. The mechanism of the superstructure formation has been discussed in relation to the unique characteristics of stiff polymer chains with the aid of an off-lattice Monte Carlo simulation.     

Resonance CARS study of long-lived species of diphenylhexatriene generated by monophotonic excitation in polar solvent

The transient absorption and resonance CARS (coherent anti-Stokes Raman scattering) spectra of photo-excited all-trans-1,6-diphenyl-1,3, 5-hexatriene (DPH) were studied and a hitherto unknown species was detected from the spectrum observed for an acetone solution. The excited species was generated by monophotonic excitation at 337 nm (ascertained from the dependence of the CARS intensity and that of the transient absorption on the UV power). A lifetime of ≈ 2 μs was obtained by time-resolved CARS. The new species was tentatively ascribed to a radical cation because of its anomalously long lifetime, agreement of the absorption maximum, and disagreement of CARS signals from those of DPH in the S₁ and T₁ states and from those of the radical anion.     

Scopadulcic acid B, a new tetracyclic diterpenoid from Scoparia dulcis L. Its structure, H+, K(+)-adenosine triphosphatase inhibitory activity and pharmacokinetic behaviour in rats

The structure of scopadulcic acid B (2, SDB), a major ingredient of the Paraguayan herb "Typychá kurat?" (Scoparia dulcis L.), was elucidated mainly by comparison of its spectral data with that of scopadulcic acid A (1). SDB inhibited both the K(+)-dependent adenosine triphosphatase (ATPase) activity of a hog gastric proton pump (H+, K(+)-ATPase) with a value of 20-30 microM for IC50 and proton transport into gastric vesicles. Pharmacokinetic studies of SDB in rats indicated that plasma SDB concentrations after i.v. injection of the sodium salt of SDB (SDB-Na) were described reasonably well by a two-compartment open model with Michaelis-Menten elimination kinetics. Plasma concentrations after oral administration of SDB-Na or SDB showed a much slower decline than what was expected following the i. v. study. It was suggested that the sustained plasma level of SDB after oral administration of SDB-Na or SDB was accounted for by relatively slow but efficient gastro-intestinal absorption in rats.     

Equilibrium concentration of trioxane in cationic polymerization

In the cationic polymerization of trioxane and tetraoxane near room temperature, the equilibrium trioxane concentration is not negligible during polymerization. In this work, tetraoxane was polymerized with BF₃ ? O(C₂H₅)₂ in various solvents and the equilibrium concentration of trioxane produced during the polymerization of tetraoxane and equilibrated with the growing polyoxymethylene chain was determined. The equilibrium trioxane concentrations were 0.05, 0.13, and 0.19 mole/l. in benzene, ethylene dichloride, and nitrobenzene at 30°C, respectively, and 0.20 mole/l. in thhylene dichloride at 50°C. The values in ethylene dichloride showed that the approximate values of ΔH_p and ΔS were ?4.2 kcal/mole and ?9.7 cal/mole-deg., respectively.     

Stereospecific synthesis of (5E)-PGE2 by palladium-catalyzed decarboxylative 2-alkenylation of 2-alkenyloxycarbonylated cyclopentanone derivative

(5$\text{E}$)-Prostaglandin E₂ methyl ester was synthesized from ($\text{R}$)-4-$\text{t}$-butyldimethylsiloxy-2-cyclopentenone by $\text{in}$$\text{situ}$ 2-alkenyloxycarbonylation of the organocopper conjugate-addition adduct followed by intramolecular palladium-catalyzed decarboxylative 2-alkenylation. A ($\text{E}$)-2-butenylated cyclopentanone derivative was obtained from either 2-[($\text{E}$)- or ($\text{Z}$)-2-butenyloxy-carbonyl]cyclopentanone derivative under the similar reaction condition.