Spin-symmetry forbidden properties of free-radical cycloadditions

Stabilities of free radicals with linear, Hückel and Möbius Hückel conformations are investigated on the basis of the stability conditions of the RHF solutions. The spin-symmetry forbidden properties of free-radical cycloadditions are discussed in terms of the above stability analyses.     

Persistent polarization in poly(vinylidene fluoride). II. Piezoelectricity of poly(vinylidene fluoride) thermoelectrets

The piezoelectricity of PVDF thermoelect rets formed with vacuum-coated aluminum electrodes has been investigated in detail. The piezoelectricity depends on the β-form crystal structure of PVDF homopolymer and copolymers. However, the piezoelectricity is not attributed to the stress dependence of the spontaneous polarization of β-form crystals, but rather to the persistent polarization arising from trapped charges. The trapping mechanism is discussed.     

Solvent-induced morphological change of microporous hollow fiber membranes

Microporous polyethylene hollow fiber membranes (EHF-1 and EHF-2) were subjected to solvent treatment, and the effects of this treatment on membrane morphology and permeating properties were studied. Membranes treated with various organic solvents exhibited enhanced permeability, enlarged pore size, and increased shrinkage in the longitudinal direction. These phenomena were found to depend on the surface tension of the solvent: the higher the surface tension of the solvent, the larger the change in morphology and permeation of the membrane. A mechanism to account for the effects of solvent treatment on the morphology of the membrane is proposed taking into consideration the influence of the type of solvent used for treatment. The enhanced morphological and permeation changes are ascribed to the formation of liquid bridges between two microfibrils of the membrane during drying followed by the deformation and adhesion of the adjacent microfibrils based on the surface tension of the solvent.     

Excitation to symmetry forbidden vibronic levels in the 1B2u state by controlled electron impact on benzene

The ¹B_2u-¹A_1g fluorescence emission of benzene excited by controlled electron impact was measured in the 14 – 100 eV region. The optically forbidden 6° levels were preferentially, excited. This indicates that a non-dipole transition takes place under low-energy electron-molecule collisions.     

Recording a binary computer-generated hologram on a thermoplastic film

A computer-generated hologram was recorded on a thermoplastic film using an electron-beam recording device. The hologram was a binary one of detour phase type and of surface relief type. A bright image was reconstructed from the recorded hologram.     

Polymerisation von Vinyl-monomeren mit dem binären Initiatorsystem aus N-Chlorosuccinimid und Lewis-Säuren

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