Copolymerization of 2-methylene-4-phenyl-1,3-dioxolane with electrophilic vinyl monomers through zwitterionic mechanism

Spontaneous copolymerization of cyclic ketene acetal, 2-methylene-4-phenyl-1,3-dioxolane ( I ) with common electrophilic vinyl monomers, such as methyl α-cyanoacrylate (MCA), acrylonitrile (AN), and methyl methacrylate (MMA) were investigated to further explore zwitterion polymerization method with cyclic ketene acetals. In the reaction of I with MCA and AN, spontaneous copolymerization took place at ambient temperature. The copolymers of I with MCA gave low molecular weight polymers, but copolymers obtained with I and AN were high molecular weight polymers. In the reaction of I and MMA, high molecular weight copolymer was obtained only at temperatures above 80°C. Thus, obtained polymers were not the alternating copolymers and possessed high I content in all the cases. From the above results, macrozwitterionic mechanism was suggested as discussed.     

Electron microscope observation of lattice defects in the FeCr σ-phase

The lattice image of the FeCr σ-phase was observed by high-resolution electron microscopy with the c axis of the tetragonal cell parallel to the incident beam. It was found that bright dots of the observed image correspond to the positions of atoms in the $\text{z = ±}\text{1}\text{4}$ planes of the σ-phase structure. Sequence faults were found in the irregular part of the lattice image. The analysis of the faults shows that an extra plane of $\text{1}\text{2}\text{a}{}_0$ width is inserted into the regular structure and one side of the fault is slightly shifted parallel to the fault plane with respect to the other side, which is consistent with the model proposed by Frank and Kasper. A unit cell step of the sequence faults was found and a model of the step was proposed.     

Effect of TRX-liposomes size on their prolonged circulation in rats

Newly formulated cationic liposomes (TRX-liposomes) with four different mean diameters were injected into twelve male rats via the lateral tail vein in order to evaluate the effect of liposomal size on pharmacokinetic parameters. TRX-liposomes disappeared from the blood according to the one-compartment model and demonstrated maximum and minimum half-lives of ca. 14 h (mean diameter of 114.3 nm) and ca. 5 h (mean diameter of 285.9 nm), respectively. This prolonged half-life tended to decrease at the boundary of 114.3 nm mean diameter. The optimal size (114.3 nm) for prolonged circulation of TRX-liposomes was consistent with that of pegylated liposomes such as Doxil((R)), however, the half-life was different among these liposomes. The electric charge of the TRX-liposomal surface is assumed to be responsible for this difference. The results of the present study will be very useful in the design of long-circulating cationic liposomes.     

Preparation of crystalline polyamides by the alternating copolymerization of aziridines and cyclic imides

The copolymerization of aziridines and cyclic imides was studied. Aziridines copolymerized alternately with cyclic imides to give crystalline polyamides. Ethylenimine and succinimide copolymerized to nylon 2,4, melting near 300°C., without any catalyst. Similarly, the corresponding crystalline polyamides were obtained from the systems of 1,2-propylenimine–succinimide, ethylenimine–glutarimide, and ethylenimine–phthalimide. The copolymerization of aziridines and cyclic imides in the presence of BF₃OEt₂ gave a copolymer which was rich in aziridine units, whereas, the addition of triethylamine had no influence on the copolymer composition. A mechanism of copolymerization was proposed based on the facts that N-tetramethylenesuccinamide was obtained by the reaction of pyrrolidine and succinimide, N-acetylethylenimine reacted with acetamide to yield N,N′-diacetylethylenediamine and that the rate of this copolymerization was dependent on the electrophilicity of imide.     

Force Measurements between Semifluorinated Thiolate Self-Assembled Monolayers: Long-Range Hydrophobic Interactions and Surface Charge

Long-range interactions between self-assembled monolayers (SAMs) of semifluorinated alkanethiols have been studied by direct force measurements in water and aqueous NaCl solutions. SAMs prepared from three different thiols, with identical fluorinated head groups but varying hydrocarbon spacer lengths, were investigated: CF(3)(CF(2))(9)(CH(2))(x)SH, where x=2, 11, or 17. Force measurements show that the interactions in water and electrolyte solutions are composed of both double-layer interactions emerging from what appears to be charges adsorbed onto the surfaces and long-range "hydrophobic" attractions, in excess of the expected van der Waals forces. The three investigated thiols produce similar results in force measurements, though the contact angles with water are slightly different. The "hydrophobic" attraction has the form of step-like attractive discontinuities in the force profiles at separations ranging from 20 to 40 nm, caused by bridging of microscopic bubbles residing at the surfaces. The shape or range of these discontinuities are not significantly affected by replacement of the water with either 1 mM or 1 M NaCl solutions. The origin of the charges causing the electrostatic double-layer interaction is unclear, but some possible causes are discussed. Copyright 2001 Academic Press.     

Solvent extraction and spectrophotometric determination of iron(II) with 2,2′-dipyridyl-2-furancarbothiohydrazone

2,2′-Dipyridyl-2-furancarbothiohydrazone (DPFTH) was used for the spectrophotometric determination of trace amount of iron(II) after the extraction process. Iron(II) can be quantitatively extracted with DPFTH in benzene from aqueous solution buffered to 3.0–8.0. The extracted species has absorption maxima at 440, 477, and 738 nm and obeyed Beer's law over the range 0–40 μg of iron in 10 ml at 738 nm. The molar absorptivity at this wave length is 1.17 × 10⁴ liters mole^?1 cm^?1. The proposed method is relatively selective for iron(II) and is satisfactorily applied to the determination of the total iron in natural waters. The proton dissociation constants of the ligand determined spectrophotometrically were pK_a1 = 2.88 and pK_a1 = 6.70 at 25 °C and μ = 0.1.     

Acylated-oxypregnane glycosides from the roots of Araujia sericifera

Twenty-three new acylated-oxypregnane glycosides were obtained from the roots of Araujia sericifera. (Asclepiadaceae). These glycosides were confirmed to be tetraglycosides possessing twelve known compounds, 12-O-benzoyllineolon, 12-O-benzoyldeacylmetaplexigenin, ikemagenin, kidjolanin, cynanchogenin, caudatin, rostratamine, penupogenin, 12-O-benzoylisolineolon, 12-O-tigloyldecylmetaplexigenin (incisagenin), 12-O-benzoyl-20-O-acetylsarcostin, 20-O-benzoyl-12-O-(E)-cinnamoyl-3 beta,5 alpha,8 beta,12 beta,14 beta,17 beta,20-heptahydroxy-(20S)-pregn-6-ene and ten new acylated-oxypregnanes, 12-O-benzoyl-20S-hydroxyisolineolon, 12-O-tigloyllineolon, 12-O-salicyloyllineolon, 12-O-salicyloyldeacylmetplexigenin, 12-O-benzoyl-3 beta,5 alpha,8 beta,12 beta,14 beta,17 beta-hexahydroxypregn-6-en-20-one, 12-O-benzoyl-19-benzoyloxydeacylmetapleligenin, 12-O-benzoyl-19-benzoyloxy-20-O-acetylsarcostin, 12-O-benzoyl-19-salicyloyloxy-20-O-acetylsarcostin, 12-O-benzoyl-5 alpha,6 alpha-epoxydeacylmetaplexigenin, and 12-O-benzoyl-5 alpha,6 alpha-epoxylineolon as their aglycones, using both spectroscopic and chemical methods.     

Vinyl polymerization. 413. Polymerization of vinyl monomer initiated by poly(vinylbenzyltrimethyl)-ammonium chloride

The polymerization of vinyl monomer initiated by an aqueous solution of poly(vinylbenzyltrimethyl)ammonium chloride (Q-PVBACI) was carried out at 85°C. Styrene, p-chlorostyrene, methyl methacrylate, and i-butyl methacrylate were polymerized, whereas acrylonitrile and vinyl acetate were not. The effects of the amounts of vinyl monomer, Q-PVBACI, and water on the conversion of vinyl monomer were studied. The overall activation energy in the polymerization of styrene was estimated as 79.1 kJ mol^?1. The polymerization proceeded through a radical mechanism. The selectivity of vinyl monomer was discussed by “a concept of hard and soft hydrophobic areas and monomers.”     

Photochemical study of [3(3)](1,3,5)cyclophane and emission spectral properties of [3n]cyclophanes (n = 2-6)

Thephotochemical reaction of [3(3)](1,3,5)cyclophane 2, which is a photoprecursor for the formation of propella[3(3)]prismane 18, was studied using a sterilizing lamp (254 nm). Upon photolysis in dry and wet CH2Cl2 or MeOH in the presence of 2 mol/L aqueous HCl solution, the cyclophane 2 afforded novel cage compounds comprised of new skeletons, tetracyclo[6.3.1.0.(2,7)0(4,11)]dodeca-5,9-diene 43, hexacyclo[6.4.0.0.(2,6)0.(4,11)0.(5,10)0(9,12)]dodecane 44, and pentacyclo[6.4.0.0.(2,6)0.(4,11)0(5,10)]dodecane 45. All of these products were confirmed by the X-ray structural analyses. A possible mechanism for the formation of these photoproducts via the hexaprismane derivative 18 is proposed. The photophysical properties in the excited state of the [3n]cyclophanes ([3n]CP, n = 2-6) were investigated by measuring the emission spectra and determining the quantum yields and lifetimes of the fluorescence. All [3n]CPs show excimeric fluorescence without a monomeric one. The lifetime of the excimer fluorescence becomes gradually longer with the increasing number of the trimethylene bridges. The [3n]CPs also shows excimeric phosphorescence spectra without vibrational structures for n = 2, 4, and 5, while phosphorescence is absent for n = 3 and 6. With an increase in symmetry of the benzene skeleton in the [3(3)]- and [3(6)]CPs, the probability of the radiation (phosphorescence) process from the lowest triplet state may drastically decrease.     

Ionic conductivity of superionic conducting glasses in the pseudobinary system AgIAg2MoO4

The ionic conductivity was measured in the temperature range 250–300 K as a function of composition of superionic conducting glasses in the pseudobinary system AgIAg₂MoO₄. The conductivity, ranging from 10^?2 to 10^?4 Ω^?1 cm^?1 at room temperature, increases linearly in logarithmic scale with increasing AgI content, while the total silver ion concentration remains nearly constant in the whole glass-forming region of the present system. Such a composition dependence of conductivity is considered to be evidence that only a fraction of the silver ions in glass contributes to the ionic conduction. The conductivity and the activation energy for conduction differ slightly between bulk glasses and pressed pellets of pulverized glasses. The close agreement in bulk glasses and pellets suggests that bulk rather than grain boundary or surface diffusion dominates the conduction process in the present glasses.