Preparation of polypyrrole–polyurethane composite foam by vapor phase oxidative polymerization

Conductive polypyrrole–polyurethane composite foam was prepared by vapor phase polymerization of pyrrole on polyurethane foam using mixtures of FeCl₂ and FeCl₃ as oxidants. With increase in the FeCl₂/FeCl₃ ratio, the conductivity of the composite foam increased in spite of the decrease in polypyrrole content in the composite foam. Both conductivity and polypyrrole content increased with increase in the oxidant content in polyurethane. The conductivity of the composite foam is also a function of reaction temperature, and lower reaction temperatures were preferable for higher conductivity. The composite foam exhibited tensile strength and elongation comparable to those of pristine polyurethane foam. © 1995 John Wiley & Sons, Inc.     

Quasi‐static and chaotic characteristics of the natural convection field in a vertical slot

In this paper, the time‐dependent characteristics of natural convection in a vertical slot with hot and cold side walls were experimentally examined. In the experiment, the test liquid was a glycerine–water mixture (80 wt%) and the Prandtl number in the center of the slot was held constant at 295. On the other hand, the Grashof number was varied in the range between 370 and 3.06 × 10³. As a result, it was revealed that low‐pass filtering for the time evolution data of temperature made it possible to compute the largest Lyapunov exponents precisely. Secondary flow cells are observed in both chaotic and nonchaotic regions. Moreover, the secondary flow cells appeared in regions where the power spectrum of temperature fluctuation was regarded as significant and where the autocorrelation function decreased rapidly with time. © 2000 Scripta Technica, Heat Trans Asian Res, 30(1): 40–53, 2001     

Isolation of an active peptide fragment from human serum albumin and its synergism with α-tocopherol

An active peptide was isolated from hydrolysates of human serum albumin. This peptide was initially isolated by gel permeation chromatography and subsequent reversed-phase high-performance liquid chromatography. This active peptide, composed of 10 amino acid residues, was further hydrolyzed with a lysyl endopeptidase to give two peptide fragments. Only one fragment, identified as the tetrapeptide Leu-Gln-His-Lys, was found to have activity comparable to the original peptide and corresponded to the amino acid residues 103–106 of human serum albumin. Among these four amino acid residues, the His-Lys sequence seemed to be important in the occurrence of potent activity by comparison of the structural similarity with another active tetrapeptide, Asp-Thr-His-Lys, which had been previously isolated from bovine serum albumin hydrolysates. In addition, the active fragment showed potent synergism by preventing consumption of α-tocopherol during the autoxidation of linoleic acid.     

Life of Magnetic Electroless Co-P Thin Films

Effective life of electroless Co-P (2.5 wt%) thin films of about 100 nm in thickness was evaluated for both magnetic characteristics and corrosion. The Co-P films were grown on rigid Al substrates overcoated with nonmagnetic Ni-P thick films and were finally covered with electroplated Rh thin films of 120 nm - 180 nm in thickness. The life of the magnetic characteristics was defined as the time to reach 10% deviation from the initial values of Hc (coercive force), Br (remanence), and S (squareness of hysteresis loop). The life of the films for corrosion was defined as the induction period of corrosion. An increase of Hc was observed above 80°C for isothermal annealing, but Br and S were unchanged. The activation energy of the variation of Hc was approximately 0.7 eV below 144°C. The life of magnetic characteristics was estimated to be approximately 4.1 × 104 ? 2.3 × 105 hrs at 55°C corresponding to the allowable maximum temperature in field service. The life for corrosion was influenced by the quality of Rh films.     

Influence of Particle Diameter on Surface Silanol Structure, Hydration Forces, and Aggregation Behavior of Alkoxide-Derived Silica Particles

The effects of silica particle diameter on dispersion and aggregation behavior in water were analyzed, using alkoxide-derived silica powders with particle diameters of 8–260 nm. The present study focused on the relationships between the surface silanol structure and the interaction forces between solid surfaces in water. The surface silanol structure and interaction between particles were determined using Fourier transform infrared spectroscopy, Fourier transform near-infrared spectroscopy, and atomic force microscopy. For relatively large particles (>30 nm in diameter), the surface silanols primarily were hydrogen-bonded silanols, and isolated silanols disappeared. The hydrogen-bonded silanols formed a hydrogen-bonded water layer on the particle surface; therefore, the additional hydration force was strong between these relatively large particles. In contrast, the surface density of isolated silanols increased as the particle diameter decreased to <30 nm, and the additional hydration force between ultrafine powders disappeared. The aggregation behaviors of alkoxide-derived silica powders were dependent on the hydration force, which was changed by the surface silanol structure.     

Transient absorption spectroscopy of polymer-based thin-film solar cells

Polymer-based solar cells have made great progress during the past decade and consequently are now attracting extensive academic and commercial interest because of their potential advantages: lightweight, flexible, low cost, and high-throughput production. On the other hand, the recent progress in analytical tools has profoundly enhanced our understanding of the underlying mechanism of polymer-based solar cells, which can provide valuable guidelines for materials design and device engineering and therefore is essential for further improvement of the device performance. In particular, transient absorption spectroscopy is a powerful tool for directly observing ultrafast fundamental processes in polymer-based solar cells. In this article, we first give a brief overview of the basic mechanism of polymer-based solar cells, and the recent progress in the device performance based on the development of materials. We review the method of assigning charge carriers generated in polymer/fullerene solar cells, the dynamics of fundamental processes, and the efficiency of each photovoltaic conversion process.     

The effect of the structural order of isotactic polypropylene containing magnetically aligned nickel particles on its electrical resistivity

The effect of the high order structure of an isotactic polypropylene (PP) composite on the resistivity of composites containing magnetically aligned Ni particles was studied. Only a small amount of particles needed to be added for the composite material to become conducting after heating while in a magnetic field. The Ni columns formed on applying the field were distorted by the formation of large PP spherulites. Changes to the crystallization process due to the addition of a nucleating agent gave rise to changes in the columnar structure, resulting in large changes in the resistivity of the composite material. Controlling the high order structure of the polymer matrix including its morphology is very important in order to be able to control the magnetically aligned Ni structure.     

Suppression of Problematic Compound Oligomerization by Cosolubilization of Nondetergent Sulfobetaines

Numerous small organic compounds exist in equilibrium among monomers, soluble oligomers, and insoluble aggregates in aqueous solution. Compound aggregation is a major reason for false positives in drug screening, and even soluble oligomers can interfere with structural and biochemical analyses. However, an efficient way to manage the equilibrium of aggregation‐prone compounds, especially those involved with soluble oligomers, has not been established. In this study, solution NMR spectroscopy was used as a suitable technique to detect compound oligomers in equilibrium, and it was demonstrated that cosolubilization of nondetergent sulfobetaines (NDSBs) can largely suppress compound oligomerization and aggregation by shifting the equilibrium toward the monomers. The rotational correlation time was obtained from the ratio of the selective and nonselective longitudinal NMR relaxation times, which directly and quantitatively reflected the apparent sizes of the compounds in the equilibrium. The rotational correlation time of the aggregation‐prone compound SKF86002 (1 mM ) was substantially reduced from 0.31 to 0.23 ns by cosolubilization of 100 mM NDSB195. NDSB cosolubilization allowed us to perform successful structural and biochemical experiments with substantially fewer artifacts, which represents a strategy to directly resolve the problematic oligomerization and aggregation of compounds.