A study of novel heat-resistant polymers: Preparation of photosensitive fluorinated polybenzoxazole precursors and physical properties of polybenzoxazoles derived from the precursors

A series of novel photosensitive polybenzoxazole precursors were prepared from polycondensation of 2,2-bis(3,3′-amino-4,4′-hydroxyphenyl)hexafluoropropane with photosensitive dicarboxylic acid chlorides such as p-phenylenediacryloyl chloride and benzophenone-4,4′-dicarboxylic chloride. The precursors are soluble in common organic solvents owing to the presence of perfluoromethyl groups in the chain structure, and insolubilized in the solvents on irradiation with the light. Polybenzoxazole patterns with high resolution as well as high aspect ratio were reproduced by baking the precursor patterns at 300°C. The pattern shrinkage on the conversion to polybenzoxazole was slight. The polybenzoxazole films offered good heat-resistance up to 400°C in addition to good electrical properties.     

Topologically conjugate Kleinian groups

Two Kleinian groups and are said to be topologically conjugate when there is a homeomorphism such that . It is conjectured that if two Kleinian groups and are topologically conjugate, one is a quasi-conformal deformation of the other. In this paper generalizing Minsky's result, we shall prove that this conjecture is true when is finitely generated and freely indecomposable, and the injectivity radii of all points of and are bounded below by a positive constant.

     

trans-2,2'-Bi(1-phenyladamantylidene): the most twisted biadamantylidene

The Grignard coupling of 2,2-dibromo-1-phenyladamantane gave trans-2,2'-bi(1-phenyladamantylidene) (1-Ph). Single-crystal X-ray analysis indicated that 1-Ph has a 23.2 degrees twisted double bond, which is much more distorted than that of parent 2,2'-biadamantylidene (1-H) and that of the ethyl-substituted derivative (1-Et). A cyclic voltammogram showed a reversible electron oxidation wave at 0.87 V vs Fc/Fc(+), which is 0.19 V lower than 1-H, indicating a significant increase in the HOMO energy level due to the distortion. The reaction of 1-Ph with 0.9 equiv of bromine gave an intramolecular Friedel-Crafts alkylation product, while bromination of 1-H and 1-Me has been reported to give a bridged bromonium ion and a rearranged product, 2-(1-methyl-2-adamantylidene)-4-bromotricyclo[5,3,1,0(3.9)]undec-4-ene, respectively.     

Ground-state α-decay of N = 128 isotones 216Ra, 217Ac and 218Th

The α-decay properties of very short-lived N = 128 isotones, ²¹⁶Ra, ²¹⁷Ac and ²¹⁸Th, were investigated by the pulsed-beam method. Alpha emitters of interest were produced in the bombardment of ²⁰⁸Pb or ²⁰⁹Bi with 65–96 MeV ¹²C or ¹⁴N ions and α-decays were measured between natural beam bursts of the cyclotron. The results obtained are _Eα = 9.349±0.008 MeVand $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 182±10}\text{ns for}{}^{216}\text{Ra}\text{, 9.650±0.010}\text{MeV}$ and $\text{111±7}\text{ns for}{}^{217}\text{Ac}\text{, 9.665±0.010}\text{MeV}$ and $\text{96±7}\text{ns for}{}^{218}\text{Th}$. The experimental reduced α-widths of N = 128 isotones from ²¹²Po to ²¹⁸Th are shown to agree well with the simple shell model calculation.     

Penetration of ammonia molecule into ice film; activation energy analysis using Xe molecular beam irradiation

We have investigated the barrier energy for an ammonia molecule to penetrate into ice film by the use of infrared spectroscopy and Xe supersonic beam. After the ice film on a Pt(1 1 1) surface is exposed to ammonia molecules, an umbrella mode of ammonia molecules adsorbed on the ice film has been observed in infrared spectra. After the irradiation of accelerated Xe beam, we observed an energy shift of the mode of ammonia. The shifted mode is assigned to that of ammonia molecules at the interface between the ice film and the Pt(1 1 1) surface. This indicates that the collision with Xe beam induced the penetration of an ammonia molecule to the interface through the ice film. Using this feature, we estimate a barrier for penetration as 0.28 ± 0.03 eV which is much smaller than the one previously reported for bulk ice.     

Collinear fast atomic-beam laser spectroscopy at riken garis/igisol

We have constructed a fast atomic-beam collinear laser spectroscopy system connected to the on-line isotope separator facility GARIS/IGISOL at RIKEN. This system is potentially powerful in studying refractory elements. To test the system, an off-line collinear experiment was made on stable Hf isotopes produced by means of laser ablation technique. For production of radioactive Hf isotopes, the use of the inverse kinematics of a fusion reaction,⁹Be(¹⁶⁶Er,xn)^175-x Hf, was investigated. The radioactive isotope¹⁶⁹Hf was successfully extracted from GARIS/IGISOL and accelerated up to 30 keV.     

Spectral and related properties about the Emden-Fowler equation −Δu=λe u on circular domains

The first author is on leave from the Department of Mathematics, Chiba Institute of Technology, Narashino 275, Japan     

Redox-controlled, reversible rearrangement of a tris(2-pyridylthio)methyl ligand on nickel to an isomer with an “N,S-confused” 2-pyridylthiolate arm

Interchange between the nickel +2 and +3 oxidation states precisely controls the reversible rearrangement of the tris(2-pyridylthio)methanide (tptm) ligand in the organometallic nickel(II) complex [{Ni(μ-Br)-(tptm)}(2)] (2). Oxidation of 2 first gives the corresponding Ni(III) complex [{Ni(μ-Br)(tptm)}(2)][PF(6)](2) (4). However, in solution the tptm ligand in 4 slowly undergoes a rearrangement, in which the N and S atoms of one of the pyridylthiolate arms exchange Ni and C bonding partners, thereby resulting in an "N,S-confused" isomer of tptm in the product, [NiBr(bpttpm)]PF(6) (5; bpttpm= bis(2-pyridylthio)(2-thiopyridinium)-methyl). Reduction of 5 reverses this ligand rearrangement and 2 is reformed quantitatively. The individual steps involved in these unusual ligand rearrangements were investigated by a number of methods, including voltammetric analysis, and a mechanism for this process is proposed. X-ray crystal structure determinations of the key compounds 2, 4 and 5 have been obtained.     

Structural studies of phase transitions in crystalline and liquid halides (ZnCl<Subscript>2</Subscript>, AlCl<Subscript>3</Subscript>) under pressure

The results of investigating the phase diagrams of ZnCl₂ and AlCl₃ halides, as well as the structure of the shortrange order of the corresponding melts under pressures up to 6.5 GPa, by the method of energy-dispersive x-ray diffraction are reported. When a ZnCl₂ crystal is compressed, a phase transition occurs from the γ phase (HgI₂ structure type) to the δ phase (distorted CdI₂ structure, WTe₂ type). The structural studies of the liquid state of ZnCl₂ and AlCl₃ indicate that the intermediate-range order decreases rapidly in the tetrahedral network of both melts as the pressure increases to 1.8 and 2.3 GPa for ZnCl₂ and AlCl₃, respectively. With further compression, the transitions in both melts occur with a change in the structure of the short-range order and with an increase in the coordination number. In this case, the transition in AlCl₃ occurs at ≈4 GPa and is a sharp first order transition, whereas the transition in ZnCl₂ occurs more smoothly in a pressure range of 2–4 GPa with a maximum intensity near 3 GPa. Thus, the AlCl₃ and ZnCl₂ compounds exemplify the existence of two phenomena—gradual decay of intermediate-range structural correlations and a sharper liquid-liquid coordination transition.