Studies on tack of pressure–sensitive adhesive tapes

It has been found that tack values of pressure-sensitive adhesives are dependent on the surface energies for adherends. The parabolic curves with maxima are obtained from the plots of tack values versus critical surface tensions for the substrates. The maximum occurs at the region where the two surface tensions are almost similar. On the other hand, tack is measured as a dynamic value indicated as the force necessary to deform the adhesive mass. To explain why the tack values is controlled by the surface character of the adherend, a mechanism is proposed for adhesive bond breaking. Primarily, bonding occurs by wetting the surface with adhesive. When the adhesive bond breaks by external force, unbonding proceeds from the viscoelastic deformation of the adhesive mass around the wetted spots on the surface of the adherend. As the total area of wetted spots is determined by surface energy, the tack value is dependent on the critical surface tension of the adherend.     

Studies of the fluorescent products of lipid oxidation in aqueous emulsion with glycine and on the surface of silica gel

The formation of fluorescent products in the reaction of methyl linoleate hydroperoxide with glycine in aqueous emulsions correlated directly with the decrease in diene conjugation and the increase in thiobarbituric acid (TBA) reactive substances. These correlations also were reflected in the course of the oxidation of methyl linoleate in aqueous emulsions with glycine and indicated that glycine reacted with products of peroxide decomposition as opposed to intermediates of autoxidation in hydroperoxide formation. Thin layer chromatography (TLC) and selective solvent extraction demonstrated that the products of the reaction contained many substances with a fluorescent spectrum similar to those of lipofuscin pigments. When methyl esters of polyunsaturated fatty acids or other polyunsaturated lipids underwent oxidation adsorbed on silica gel particles, products with similar fluorescent spectral properties were formed illustrating that fluorescent substances were formed in a variety of reactions associated with the oxidation of unsaturated lipids.     

Preparation of Matrix-Type Nickel Oxide/Samarium-Doped Ceria Composite Particles by Spray Pyrolysis

Matrix-type nickel oxide (NiO)/samarium-doped ceria (SDC) composite particles, in which NiO and SDC nano-particles were homogeneously dispersed, were synthesized by spray pyrolysis (SP) for an anode precursor of intermediate-temperature solid oxide fuel cells (IT-SOFCs). SP of an aqueous solution containing Ni, Ce, and Sm salts resulted in capsule-type composite particles that had NiO enveloped with SDC. The capsule-type composite particles actually prevent Ni aggregation between particles, but they cannot have a large contact area between nickel (Ni) and SDC. A matrix-type composite particle is expected to have a large contact area because the matrix-type composite is comprised of nanometer-sized Ni and SDC particles. An adequate addition of ethylene glycol successfully resulted in matrix-type NiO/SDC composite particles. The matrix-type composite particles also showed higher anode performance than the capsule-type composite particles in these experiments and they were effective as precursors of high-performance IT-SOFC anodes.     

Synthesis and conformational studies of polymers and copolymers of O,O′-dimethyl-l-β-3,4-dihydroxyphenyl-α-alanine with γ-benzyl-l-glutamate

Eight different copolymers of $\text{O,O′-}\text{dimethyl-}\text{l}\text{-β-3,4-}\text{dihydroxyphenyl}\text{-α-}\text{alanine}$ ($\text{O,O′-}\text{dimethyl-}\text{l}\text{-}\text{Dopa}$) and γ-benzyl-l-glutamate with degrees of polymerization of 320-80 have been synthesized by the N-carboxyanhydride method. From the results obtained by a study of the optical rotatory dispersion and circular dichroism for the copolymer series, the conformation of $\text{poly}\text{(O,O′-}\text{dimethyl-}\text{l}\text{-Dopa}\text{)}$ is a right-handed helix in helicogenic solvents such as chloroform, dioxane or 2-chloroethanol. Copolymers containing less than 50 mol % glutamate show a circular dichroism peak at 285 nm suggesting stacking of aromatic groups in the side chain. $\text{Poly}\text{(O,O′-}\text{dimethyl-}\text{l}\text{-Dopa}\text{)}$ is in the random coil structure in trifluoroacetic acid or hexafluoroacetone. The results were compared with those of $\text{poly}\text{(O,O′-}\text{dicarbobenzoxy-}\text{l}\text{-Dopa}\text{)}$ and poly(l-Dopa).     

Fabrication of wrinkled carbon nano-films with excellent field emission characteristics

B-doped nano-structured carbon films were deposited on Si substrates by means of chemical-vapour-deposition with 3.8-kW microwave-plasma. Scanning electron microscope images show that the deposited films were composed of wrinkled graphitic nano-sheets with considerable disorder structures. Field emission (FE) characteristics measured from such films yielded considerably high FE currents, being larger than 50 mA/cm² at a macroscopic electric field of 9.5 V/μm. A possible mechanism of the observed FEs is discussed in relation to a modified Fowler–Nordheim equation considering field-dependent parameters. As a result, it is found that the structure of the surface geometry mainly increased the FE current densities. Adding a suitable amount of B-component gas to the carbon source gas resulted in a considerable increase in the FE areas of the wrinkled carbon nano-films.     

Oxygen Self-Diffusion in Single-Crystal Y2O3

Self-diffusion coefficients of the oxygen ion in single-crystal Y₂O₃ were determined by the gas-solid isotope exchange technique. The results in the range 1100° to 1500°C are described by D=7.3 X 10^-6 exp [-19l(kJ/mol)/RT] cm²/s. Comparison of the results with those for oxides with the fluorite-type structure indicates that the regularly arranged vacant anion sites in the C-type structure do not contribute eflectively to oxygen ion diffusion .     

Highly ion conductive flexible films composed of network polymers based on polymerizable ionic liquids

Ionic liquid-type polymer brushes having different hydrocarbon (HC) chain lengths between polymerizable group and imidazolium ring were synthesized. When the carbon number of HC chain was 6, the ionic liquid-type polymer brush exhibited the highest ionic conductivity of 1.37×10⁻⁴ S cm⁻¹ at 30 °C, reflecting low T_g of −60 °C. Moreover, for the first time, we succeeded in obtaining transparent and flexible films without considerable decrease in the ionic conductivity as compared with that of corresponding monomers by using suitable cross-linkers. The most ion conductive (1.1×10⁻⁴ S cm⁻¹ at 30 °C) film was obtained when tetra(ethylene glycol)diacrylate was used 0.5 mol% to ionic liquid monomer as the cross-linker. This film is one of excellent conductive films among single-ion conductive materials.     

Study of the properties of nickel oxide and nickel as precursors for the tartaric acid-NaBr-modified nickel catalyst

Nickel oxide was prepared by the decomposition of nickel hydroxide and then the nickel oxide was reduced to form the nickel catalyst. The properties of the nickel oxide and the reduced nickel were studied in relation to the enantio-differentiating ability (e.d.a.) of a tartaric acid-NaBr-modified reduced nickel catalyst. The modified nickel catalyst prepared from nickel oxide with less non-stoichiometric oxygen produced a high e.d.a. for the hydrogenation of methyl acetoacetate. The high crystallinity of the nickel oxide and the resultant nickel would be required to attain a high e.d.a.     

Contribution of primary radical termination to radical polymerization of diethyl fumarate estimated from absolute rate constants

Summary Diethyl fumarate was radically polymerized under UV irradiation and concentration of the propagating radical was determined to be of the order of 10^-5 mol/L by scavenge with a stable free radical. The absolute rate constant for propagation (k_p) was evaluated from the overall rate of polymerization at 30°C: K_p =(2.9 ± 0.3) × 10^-2 L/mol · s. The rate constant for mutual termination of the polymer radical (k_t) was calculated from the decreasing rate of the radical concentration in the dark: k_t=8.0 L/mol·s. The k_t value determined is one twentieth of that evaluated previously by a rotating sector method. This discrepancy is accounted for by contribution of much faster primary radical termination.     

Intermediate hydrocarbon species for the CO2-CH4 reaction on supported Ni catalysts

By using pulse surface reaction rate analysis (PSRA), the detailed structure of the intermediate hydrocarbon species was revealed by measuring the dynamic behavior of both CO and H₂ produced from the CO₂-CH₄ reaction on supported Ni catalysts. It was found that the number of hydrogen atoms involved in the intermediate was different from one catalyst support to another: 2.7 for MgO, 2.5 for ZnO, 2.4 for Al₂O₃,1.9 for TiO₂, and 1.0 for SiO₂.