Advanced Materials Research Vols. 11-12

Abstract: Bacterial photosynthetic antenna complexes are composed of α-helical hydrophobic polypeptides and pigments (e.g., bacteriochlorophyll a). We report here self-assembling properties of an engineered hydrophobic polypeptide with zinc-substituted bacteriochlorophyll a ([Zn]-BChl a) in various lipid bilayer to investigate the effect of lipid species on the self-assembling properties. When the polypeptide and [Zn]-BChl a were mixed in surfactant solution (n-octyl β-D-glucopyranoside: OG) at 25°C, the absorption band [Zn]-BChl a was red-shifted from 770 to 812 nm, that is assignable to quasi-dimeric “subunit-type” complex. By subsequent dilution and cooling of the solution, the absorption band further red-shifted to 836 nm indicative for progressed assembly, ‘LH1-type’ complex. When the subunit-type complex was assembled in lipid bilayer, e.g., phosphatidylcholines (PC’s) and phosphatidylglycerol (PG’s), the assembling property to form LH1-type complex prominently depended on the character of their fatty acid chains in the phospholipids. The subunit complex remained in the fluidic bilayers, but further assembled to form LH1-type complex in solid-like phospholipid bilayers, suggesting that intermolecular force of phospholipid governs the assembling of the polypeptide/[Zn]-BChl a complex.

Abstract: Monodisperse polystyrene (PS) particle multilayer with coherent structure was
constructed by Langmuir-Blodgett (LB) method. The reflectance spectra of the particle multilayer with various incident angles indicated that the constructed particle multilayer showed a typical optical character of the conventional multilayer having different refractive index. It was suggested that the particle multilayer was treated as a multilayer constructed by polymer layer and air layer. The fact was strongly supported by a simulation of the corresponding model, which was designed for analyzing optical characterization of the particle multilayer. The refractive index of the particle multilayer with nickel ion was also discussed by simulation, suggesting that a theoretical designing of the particle multilayer with various refractive index would be possible. It was also suggested that coordination of metal ion on the surface of the particle would be enhanced its contribution for increasing the refractive index.

Abstract: SiO2 thin-films were prepared by thermal oxidation method. It showed uniform color based on the thin-film interference of visible light. Then we made biotin antenna on the top of SiO2 thin-film. Biotin is one of the vitamins and it has high association constant with protein avidin. After immersed the substrate into avidin solution, certain color changes based on the self-assembling of avidin on its surface were observed. By the immersing these substrates into mono-dispersed polystyrene particle solution, a polystyrene particle layer was formed onto avidin SAMs and it brought dynamic interference color change. As a result, this substrate could sense the avidin molecules over 1.0×10-8M of its concentration by naked eyes.

Abstract: In order to construct an intelligent functional nano-interface, the self-organized structure of Langmuir-Blodgett (LB) film was investigated by atomic force microscopy (AFM). As a building block, a monodisperse loop-helix-helix triblock copolypeptide containing the helix of which hydrophobic L-leucine residues align on a single face, “leucine zipper”, was synthesized by recombinant DNA techniques with a designed amino acid sequence. AFM observation on the surface structure of LB films constructed at surface pressures of 2, 5 and 18 mN/m revealed that structural transition from ring- or disk-like aggregations to a lane-like fabrication occurred with compression of the copolypeptide membrane on the water of pH 4. The leucine zipper in the copolypeptide was suggested to perform as an important basis for nanostructure formation through a hydrophobic interaction. Exploitation of the recognition and specific binding sites in the copolypeptide will allow the self-assembling mechanism of the copolypeptide to be developed to a novel nano-template.

Abstract: Multistage open association (MSOA) and helical growth (HG) mechanisms describe the linear growth of supramolecular polymer chains and the helical growth of supramolecular chains with the intra-assemble cooperative effect, respectively. Both mechanisms were proposed by Ciferri. Assuming that supramolecular polymerization follows the step-growth and the interaction between repeat units is independent of molecular weight, the kinetics of MSOA and HG can be mathematically analyzed. In this paper the relationships among degree of polymerization (DP), unimer concentration (C0), and equilibrium constant (K) for MSOA and DP , concentration of helical polymer ( h C ), and nucleation factor (σ ) for HG were derived.

Abstract: Amphiphilic diblock copolymer was synthesized in one-step or two-step process by using of methoxy polyethylene glycol (MePEG), 1,6-hexanediol and maleic anhydride and characterized by FTIR and GPC. IR spectrum of amphiphilic diblock copolymer confirmed that MePEG had grafted on polyester. Solution polycondensation, melt polycondensation, mode of adding monomers and reaction time were studied on effect of molecular weight and its distribution. The GPC results showed that fairly narrow molecular weight distribution was obtained in solution polycondensation by one-step process. In addition, self-assemble behavior of amphiphilic diblock copolymer was discussed in different solvents by nanoprecipitation technique. The micelle size and aggregation was measured by TEM. It was found that MePEG1900-b-Polyester2162 copolymer self-assembled in acetone solution against water into well core-shell nanoparticles.

Abstract: The AZ31 Mg alloy thin sheets were hot-rolled by using a small-sized rolling mill. The thickness was successfully reduced to 0.6 mm without surface crack in 150mm×50 mm area. The effect of rolling deformation on microstructure of the thin sheets was investigated. The basic α-Mg phase preferred on (0001) plane and had equiaxed grains with an average grain size of about 20 μm. All cross sections parallel to the rolling direction showed a streamline-like microstructure due to the strong working strain during hot rolling. The precipitates were remarkably refined to less than 5 μm.

Abstract: AZ31B Magnesium alloy sheets with about 1 mm in thickness were rolled by one pass and several passes from the extruded ingots with different thickness. The effects of processing variables on microstructure and mechanical properties of AZ31B Mg alloy sheets were investigated. XRD indicated that AZ31B magnesium alloy sheets have a dominant texture with (000l) orientated plane. The large deformation results in the formation of fine and homogeneous microstructure due to the recrystallization during extruding and hot-rolling. The thinnest sheet rolled by several passes showed equiaxed grains with 5-10μm in diameter. The fine grains result in the increase in the strength and the ductility. The tensile strength of the sheet rolled by several passes reached 292 MPa and the elongation was twice as larger as that rolled by one pass.

Abstract: The bonding properties between the solution polymerized styrene-butadiene rubber (SSBR) and 2A70 aluminum alloy with treatment of anodic oxidation by sulfuric acid or ethane acid were investigated. The influences of three treating methods were also studied. Two drying methods, which are vacuum method and normal pressure method affected on the properties of adhesive molecular immerging into the hole dispersing on the surface of aluminum alloy, were discussed. The results revealed that prolonging the time for anodic oxidation by both sulfuric acid and ethane acid can increase the thickness of the aluminum oxide layer.

Abstract: In diffusion-rolling bonding, bonding temperature is a key parameter influencing interface bonding strength. In this case, lab experiments were carried out in a vacuum furnace to simulate the diffusion-rolling bonding of steel sheet of polycrystal structures under different temperatures. Bonding strength and interlayer film thickness were measured. The relationship between bonding strength and “diffused interlayer” thickness
λ was investigated. The effect of temperature on diffusion-rolling bonding was investigated. Diffusion mechanism was qualitatively discussed. Based on above diffusion mechanism, the transformation in phase structure and its effect on the diffusion coefficient under different temperature was also analyzed and compared with the experimental results.