Migration and blooming of waxes to the surface of rubber vulcanizates

When certain substances, notably waxes, are incorporated into rubber during vulcanization, the surface of the vulcanized rubber may subsequently become covered by a film of the substance diffusing out. This phenomenon, known as blooming, depends on the substance being soluble at the vulcanization temperature but only partially soluble at the temperature of blooming. A study has been made using pure waxes in natural rubber vulcanizates with a range of crosslink densities. The mass of bloomed material has been determined as a function of time, and the expected dependence on the square root of the time has been found to hold over the anticipated range. It has been shown that the kinetics of the process cannot be explained simply in terms of the degree of supersaturation of the wax in the rubber, the observed rates being much too low. This appears to be related to the precipitation of the wax in the body of the material. A theory has been developed based on a calculation of the stresses set up around such a precipitated particle and the effect of the consequent free-energy gradient on the rate of diffusion. Comparison with experiment shows satisfactory agreement with the theory.     

Retardation of shape change of Au nanorods using photo-cross-linkable ligands

The thermal reshaping of gold nanorods has been slowed by grafting a diblock copolymer [P(S-b-S-N₃)] containing an outer polystyrene (PS) brush and a short, inner photo-cross-linkable PS-azide block. The P(S-b-S-N₃)-Au NRs were dispersed in a PS thin film and reshaping was investigated using scanning electron microscopy and UV–Vis spectroscopy. For P(S-b-S-N₃)-Au NRs in PS, the longitudinal surface plasmon resonance decreased from about 880 toward 750 nm upon annealing at 100 °C, 150 °C, and 200 °C. This blue shift increased in strength as temperature increased. However, this reshaping of P(S-b-S-N₃)-Au NRs was slower than that of Au NRs grafted with a poly(ethylene glycol) brush that was dispersed in poly(methyl methacrylate). By slowing down reshaping at elevated temperature, polymer thin film devices that heat during use (e.g., polarization dependent filters) can exhibit a longer lifetime. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 301–307     

Protective Effects of Gintonin on Reactive Oxygen Species-Induced HT22 Cell Damages: Involvement of LPA1 Receptor-BDNF-AKT Signaling Pathway

Gintonin is a kind of ginseng-derived glycolipoprotein that acts as an exogenous LPA receptor ligand. Gintonin has in vitro and in vivo neuroprotective effects; however, little is known about the cellular mechanisms underlying the neuroprotection. In the present study, we aimed to clarify how gintonin attenuates iodoacetic acid (IAA)-induced oxidative stress. The mouse hippocampal cell line HT22 was used. Gintonin treatment significantly attenuated IAA-induced reactive oxygen species (ROS) overproduction, ATP depletion, and cell death. However, treatment with Ki16425, an LPA1/3 receptor antagonist, suppressed the neuroprotective effects of gintonin. Gintonin elicited [Ca²⁺]_i transients in HT22 cells. Gintonin-mediated [Ca²⁺]_i transients through the LPA1 receptor-PLC-IP₃ signaling pathway were coupled to increase both the expression and release of BDNF. The released BDNF activated the TrkB receptor. Induction of TrkB phosphorylation was further linked to Akt activation. Phosphorylated Akt reduced IAA-induced oxidative stress and increased cell survival. Our results indicate that gintonin attenuated IAA-induced oxidative stress in neuronal cells by activating the LPA1 receptor-BDNF-TrkB-Akt signaling pathway. One of the gintonin-mediated neuroprotective effects may be achieved via anti-oxidative stress in nervous systems.     

Thermal‐ and Photo‐Induced Phase‐Transition Behaviors of a Tapered Dendritic Liquid Crystal with Photochromic Azobenzene Mesogens and a Bicyclic Chiral Center

A ribbon‐shaped chiral liquid crystalline (LC) dendrimer with photochromic azobenzene mesogens and an isosorbide chiral center (abbreviated as AZ₃DLC) was successfully synthesized and its major phase transitions were studied by using differential scanning calorimetry (DSC) and linear polarized optical microscopy (POM). Its ordered structures at different temperatures were further identified through structure‐sensitive diffraction techniques. Based on the experimental results, it was found that the AZ₃DLC molecule exhibited the low‐ordered chiral smectic (Sm*) LC phase with 6.31 nm periodicity at a high‐temperature phase region. AZ₃DLC showed the reversible photoisomerization in both organic solvents and nematic (N) LC media. As a chiral‐inducing agent, it exhibited a good solubility, a high helical‐twisting power, and a large change in the helical‐twisting power due to its photochemical isomerization in the commercially available N LC hosts. Therefore, we were able to reversibly “remote‐control” the colors in the whole visible region by finely tuning the helical pitch of the spontaneously formed helical superstructures.     

Effects of UV irradiation on physico‐mechanical properties of EPDM/buckminsterfullerene composite

Ethylene propylene diene rubber‐fullerene (EPDM/C60) composite, partially crosslinked by ultraviolet (UV) radiation, was prepared and characterized for crosslink density, mechanical properties and thermal behavior. FT‐IR analysis showed peak disappearance at 1688 cm^?1, corresponding to the unsaturation of EPDM, and the appearance of new peaks relating to the formation of oxidation products of C60, such as epoxide, keto, aldehyde and carboxylic groups. Solubility studies demonstrated the dissolution of pristine EPDM in toluene even after a longer period of UV exposure, whereas EPDM/C60 composite became insoluble and/or swollen after 6 hr of UV exposure, indicating the formation of partial crosslinking between EPDM and C60. Differential scanning calorimetry (DSC) measurements revealed an increase in the glass transition temperature peak of UV‐cured EPDM. Thermogravimetric analysis (TGA) showed that UV exposure reduced the thermal decomposition temperature of EPDM/C60, pristine EPDM and dicumyl peroxide (DCP)‐cured EPDM. The modulus, tensile stress and elongation at break of EPDM/C60 composites were greatly influenced by the duration of UV irradiation. Comparison of UV‐cured EPDM/C60 composite with DCP‐cured EPDM confirmed the superior strength properties of the former system. Copyright © 2004 John Wiley & Sons, Ltd.     

Computational Science and Engineering Online (CSE-Online): a cyber-infrastructure for scientific computing

With the expansion of the Internet and World Wide Web (or the Web), research environments have changed dramatically. As a result, the need to be able to efficiently and securely access information and resources from remote computer systems is becoming even more critical. This paper describes the development of an extendable integrated Web-accessible simulation environment for computational science and engineering called Computational Science and Engineering Online (CSE-Online; http://cse-online.net). CSE-Online is based on a unique client-server software architecture that can distribute the workload between the client and server computers in such a way as to minimize the communication between the client and server, thus making the environment less-sensitive to network instability. Furthermore, the new software architecture allows the user to access data and resources on one or more remote servers as well as on the computing grid while having the full capability of the Web-services collaborative environment. It can be accessed anytime and anywhere from a Web browser connected to the network by either a wired or wireless connection. It has different modes of operations to support different working environments and styles. CSE-Online is evolving into middleware that can provide a framework for accessing and managing remote data and resources including the computing grid for any domain, not necessarily just within computational science and engineering.     

Boosting Visible-Light Photocatalytic Redox Reaction by Charge Separation in SnO2/ZnSe(N2H4)0.5 Heterojunction Nanocatalysts

In this work, environmentally friendly photocatalysts with attractive catalytic properties are reported that have been prepared by introducing SnO₂ quantum dots (QDs) directly onto ZnSe(N₂H₄)_0.5 substrates to induce advantageous charge separation. The SnO₂/ZnSe(N₂H₄)_0.5 nanocomposites could be easily synthesized through a one-pot hydrothermal process. Owing to the absence of capping ligands, the attached SnO₂ QDs displayed superior photocatalytic properties, generating many exposed reactive surfaces. Moreover, the addition of a specified amount of SnO₂ boosted the visible-light photocatalytic activity; however, the presence of excess SnO₂ QDs in the substrate resulted in aggregation and deteriorated the performance. The spectroscopic data revealed that the SnO₂ QDs act as a photocatalytic mediator and enhance the charge separation within the type II band alignment system of the SnO₂/ZnSe(N₂H₄)_0.5 heterojunction photocatalysts. The separated charges in the heterojunction nanocomposites promote radical generation and react with pollutants, resulting in enhanced photocatalytic performance.     

Hydrophilic graft modification of a commercial crystalline polyolefin

Hydroxy‐functionalized isotactic poly(1‐butene) was synthesized using transition metal‐catalyzed regioselective C? H borylation at the side chain of the commercial polyolefin and subsequent oxidation of the boronic ester functionality. Functionalization up to ～ 19 mol % of the termini of the ethyl side chain occurred without significant side reactions that could alter the polymer chain length. Esterification of the hydroxy group in the polymer with 2‐bromoisobutyl bromide generated a side chain‐functionalized polyolefin macroinitiator. Atom transfer radical polymerization of tert‐butyl acrylate from the macroinitiator produced a high molecular‐weight graft copolymer of the polyolefin, isotactic poly(1‐butene)‐graft‐poly(tert‐butyl acrylate) (PB‐g‐PtBA). Finally, the hydrolysis of the tert‐butoxy ester group of PB‐g‐PtBA created an amphiphilic polyolefin, isotactic poly(1‐butene)‐graft‐poly(acrylic acid), which contained a short carboxylic acid‐functionalized polymer block at the side chain. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3533–3545, 2008     

Selective sensor for silver ions built from polyfluorophores on a DNA backbone

To explore a new modular metal ion sensor design strategy, fluorophores and ligands were incorporated into short DNA-like oligomers. Compound 1 was found to function as a selective sensor for Ag(+) in aqueous buffer, where low micromolar concentrations of Ag(+) induce a red-shifted, turn-on fluorescence signal. Experiments with HeLa cells show that 1 can penetrate cells and yield a signal for intracellular Ag(+). This suggests a broadly applicable approach to developing sensors for a wide variety of cations.