Structural development of ultra‐high strength polyethylene fibers: Transformation from kebabs to shishs through hot‐drawing process of gel‐spun fibers

Structural development of ultra‐high strength polyethylene fibers via hot‐drawing processes of as‐spun gel fibers was investigated by means of transmission electron microscopy. It is found that the shish‐kebabs developed in both the as‐spun and drawn fibers can be transformed continuously into the micro‐fibril structure composed mostly of the shish structure through the hot‐drawing process. The structure transformation involves a drastic decrease in diameter of the kebab plus the shish but almost no change in the shish diameter. This result suggests that the chains in the kebabs are incorporated into the shishs and consumed to extend the longitudinal dimension of the shishs during the drawing process. The proposed new deformation model well explains the relationship between the fiber morphology and their mechanical properties: the tensile strength and modulus of the fibers can be determined by the number of the shish in the fiber and the macroscopic diameter of the fiber, which are apriori determined at the spinning process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1861–1872, 2010     

Highly refractive polymer resin derived from sulfur‐containing aromatic acrylate

New sulfur‐containing polymers with high‐refractive indices and low birefringences have been developed as UV‐curable high‐refractive polymer resins. The polymers derived from 2,7‐bis[(2‐acryloylethyl)sulfanyl]thianthrene (2,7‐BAST) and 4,4′‐bis[(acryloyloxyethylthio)diphenylsulfide (4,4′‐BADS) were prepared by photopolymerization under UV irradiation. Transparent UV‐cured films were obtained in both cases. Both polymers showed good thermal stability, such as a 5% weight‐loss temperature at 355 °C under nitrogen and glass transition temperatures (T_g) in the range of 94–143 °C. They also showed high‐refractive indices of 1.6531 and 1.6645 at 632.8 nm and low birefringences of 0.0039 and 0.0069 in addition to high transparency in the visible region. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2604–2609, 2010     

Specific recognition of syndiotactic poly(methacrylic acid) in porous isotactic poly(methyl methacrylate) thin films based on the effects of stereoregularity,temperature, and solvent

The effects of stereoregularity, temperature, and solvent on the specific recognition of syndiotactic (st)‐poly(methacrylic acid) (PMAA) in macromolecularly porous isotactic (it)‐poly(methyl methacrylate) films were investigated to give important insights into the regularity and stability of nanospaces in the it‐PMMA films as well as template polymerization. The porous it‐PMMA films were fabricated on quartz crystal microbalance (QCM) substrates via the layer‐by‐layer (LbL) assembly of it‐PMMA/st‐PMAA, plus the st‐PMAA extraction from the assembly. QCM analysis and infrared spectroscopy revealed the first case of stereocomplex formation using st‐PMAA with lower stereoregularity (rr = 73%) in the LbL films, while st‐PMAA obtained with conventional free radical polymerization (rr = 62%) was barely incorporated into the porous it‐PMMA films. The maximum st‐PMAA incorporation increased from 25 to 40 °C, but there were almost no difference between 40 and 55 °C, indicating that the it‐PMMA crystallization would also be accelerated with increasing temperature. The studies on st‐PMAA incorporation with various complexing solvents revealed that the host it‐PMMA in the porous films could only form the original stereocomplex with 2/1 unit‐molar stoichiometry (st‐PMAA/it‐PMMA) in acetonitrile/water or ethanol/water. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3651–3657, 2010     

Ultrafast excited state dynamics of spirilloxanthin in solution and bound to core antenna complexes: Identification of the S∗ and T(1) states

Ultrafast excited state dynamics of spirilloxanthin in solution and bound to the light-harvesting core antenna complexes from Rhodospirillum rubrum S1 were investigated by means of femtosecond pump-probe spectroscopic measurements. The previously proposed S? state of spirilloxanthin was clearly observed both in solution and bound to the light-harvesting core antenna complexes, while the lowest triplet excited state appeared only with spirilloxanthin bound to the protein complexes. Ultrafast formation of triplet spirilloxanthin bound to the protein complexes was observed upon excitation of either spirilloxanthin or bacteriochlorophyll-a. The anomalous reaction of the ultrafast triplet formation is discussed in terms of ultrafast energy transfer between spirilloxanthin and bacteriochlorophyll-a.     

A Chemo-Enzymatic Expeditious Route to Racemic Dihexanoyl (2R*,3R*,4R*)-Dehydroxymethylepoxyquinomycin (DHMEQ), the Precursor for Lipase-Catalyzed Synthesis of the Potent Nuclear Factor-κB Inhibitor, (2S,3S,4S)-DHMEQ

In order to synthesize the potent nuclear factor (NF)-κB inhibitor, (2S,3S,4S)-dehydroxymethylepoxyquinomycin (DHMEQ), in a large scale, a new route for its corresponding racemic precursor, dihexanoyl (2R*,3R*,4R*)-DHMEQ, was developed. By employing both hydroquinone and benzoquinone intermediates, the total yield, reproducibility, and synthetic steps were improved and the synthetic cost was reduced.     

Influence of adding carbon nanotubes on photoelectric conversion properties of dye-doped titania gel

Multiwalled carbon nanotubes (MWCNTs) were incorporated into amorphous dye-doped titania gel by the sol?Cgel method at room temperature. The working electrodes were prepared by coating the ITO glass with the sol?Cgel titania precursor containing the dye and MWCNTs. The photoelectric conversion properties of the electrodes were examined by simple spectroscopic and electric measurements. The photocurrent spectrum originated from the absorption of the dye. The short circuit photocurrent was enhanced by adding a small amount of MWCNTs evenly to the amorphous dye-doped titania gel. The open circuit voltage was due to the semiconducting characteristics property of the titania gel. The experimental results indicated the electron transport from the dye excited states to the MWCNTs through the titania gel. The MWCNTs functioned as bridges between the titania and ITO. Steam treatment of the titania gel electrodes significantly increased the photoelectric performance due to crystallization of the titania and enhancement of the dye?Ctitania interaction forming the chelate complex on the titania particle surface.     

Thermodynamic Insight into the Origin of a Calix[n]arene-[60]fullerene Interaction and its Application to a Porphyrin-[60]fullerene Energy Transfer System

The calixarene-fullerene interaction,which causes only a slight change in the absorptionspectra, has been substantiated by calorimetricmeasurements: the H° values arecomparable with those obtained from the associationconstants estimated by a spectroscopic method. Furthermore, we determined the association constantbetween homooxacalix[3]arene and [60]fullerenederivatives with a porphyrin moiety by fluorescencespectra.     

分散共聚法制备特殊形态高分子微球的研究

以聚乙二醇 (PEG)大分子单体为反应性稳定剂 ,在丙烯腈的分散共聚反应中添加少量苯乙烯以形成疏水性核 ,制备得到了亚微米级高分子微球 .透射电子显微镜研究表明 ,该高分子微球具有特异的形态结构 .同时研究了分散共聚体系中各种反应因素对微球形态和直径的影响 ,结果表明 ,苯乙烯单体的添加量、PEG大分子单体的浓度及分子量、混合溶剂的组成对微球直径和形态均有明显的影响 .X 射线光电子能谱 (XPS)研究结果表明 ,微球表面聚集有亲水性PEG链 ,核为疏水的聚 (丙烯腈 苯乙烯 ) ,即形成的特异形态的PEG接枝高分子微球亦为复合型结构     

Stark absorption spectroscopy of indole and 3-methylindole

Indole and 3-methylindole (3-MI) doped into a polymethylmethacrylate (PMMA) film are studied by the Stark absorption (electroabsorption) spectroscopy. The 1La and 1Lb absorption bands are distinguished and the change in permanent dipole moment on 1La excitation is determined by a model fit to the measured absorption and electroabsorption spectra. Analysis of the spectra, measured at normal incidence and magic angle conditions, proved the essential role of the electric-field-induced orientation/alignment effects for polar indole and 3-MI molecules in the PMMA environment at room temperature.     

Application of the 19F NMR technique to observe binding of the general anesthetic halothane to human serum albumin.

19F NMR techniques were employed to characterize the binding property of the widely used general anesthetic halothane with human serum albumin (HSA). It was found that 19F(1H) NOE and 2D 1H-19F HOESY experiments detected intermolecular NOEs between halothane 19F and HSA protons. Measurements of the diffusion coefficients for halothane were also carried out by 1H and 19F NMR, indicating the interaction of halothane with HSA. The present results indicate that these techniques are very suitable to identify a fluorine-containing ligand binding with a protein receptor in the drug-discovery process.