Surlyn®/[silicon oxide] hybrid materials. 2. Physical properties characterization

The influence of an in situ‐grown, sol → gel‐derived silicon oxide filler on mechanical, gas permeation and solvent affinity properties of Surlyn® materials, and melt processibility of Surlyn®/[silicon oxide] hybrid resin, was studied. Tensile modulus increases while elongation‐at‐break decreases with increasing silicon oxide uptake. He gas permeation vs. pressure profiles imply dual mode sorption. Swelling in n‐hexane, 1‐PrOH and xylene decreases as silicon oxide loading increases, the highest uptake being that of xylene. [Surlyn®Zn⁺²]/[silicon oxide] has better solvent resistance than the H‐form hybrid for each solvent. Affinity of the Zn‐form hybrid for xylene is considerably greater than that for 1‐PrOH and n‐hexane. Melt flow index of the filled H‐form is lower than that of the unfilled H‐form but higher than that of the partially Zn neutralized unfilled form. FTIR analysis of hybrids previously subjected to the melt flow index experiment shows that the silicon oxide phase remained intact but that the high temperatures drove condensation reactions between SiOH groups. After in situ sol–gel reactions and drying [Surlyn®‐H]/[silicon oxide] flakes were passed through an extruder to assess the effect on silicon oxide structure of melt‐processing conditions. All silicon oxide IR fingerprint bands for the processed hybrid persist, the spectrum closely resembling that of a nonextruded hybrid including the signature of Si–OH groups. ²⁹Si solid‐state NMR spectroscopy was used to probe degree of molecular connectivity within the silicon oxide phase. The spectrum is consistent with those of nonextruded hybrids in that Si atom coordination around SiO₄ units is predominantly Q₃ and Q₄, the bias in the distribution toward Q₃ being in harmony with the IR results. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 143–154, 1999     

Dispersion supported transmissionwith a binary optical signal at the receiver

A novel modulation scheme for dispersion supported transmission (DST) is proposed. Instead of the binary frequency modulation of the transmitter laser a linear frequency modulation along with the differential Manchester coding is used. It is shown that it gives greater values of the extinction coefficient as compared to the previous research in the range of 100km相似文献   

Surface modification and laser pulse length effects on internal energy transfer in DIOS

Benzyl-substituted benzylpyridinium (BP) chloride salts were used as a source of thermometer ions to probe the internal energy (IE) transfer in desorption/ionization on porous silicon (DIOS). To modify their wetting properties and the interaction energies with the thermometer ions, the DIOS surfaces were silylated to produce trimethylsilyl- (TMS), amine- (NH2), perfluoroalkyl- (PFA), and perfluorophenyl-derivatized (PFP) surfaces. Two laser sources--a nitrogen laser with pulse length of 4 ns and a mode locked 3 x omega Nd:YAG laser with a pulse length of 22 ps--were utilized to induce desorption/ionization and fragmentation at various laser fluence levels. The corresponding survival yields were determined as indicators of the IE transfer and the IE distributions were extracted. In most cases, with increasing the laser fluence in a broad range (approximately 20 mJ/cm2), no change in IE transfer was observed. For ns excitation, this was in remarkable contrast with MALDI, where increasing the laser fluence resulted in sharply (within approximately 5 mJ/cm2) declining survival yields. Derivatization of the porous silicon surface did not affect the survival yields significantly but had a discernible effect on the threshold fluence for ion production. The IE distributions determined for DIOS and MALDI from alpha-cyano-4-hydroxycinnamic acid reveal that the mean IE value is always lower for the latter. Using the ps laser, the IE distribution is always narrower for DIOS, whereas for ns laser excitation the width depends on surface modification. Most of the differences between MALDI and DIOS described here are compatible with the different dimensionality of the plume expansion and the differences in the activation energy of desorption due to surface modifications.     

Optimization of boron-doping process of titania nanotubes via electrochemical method toward enhanced photoactivity

In this work, we were focused on the development of the electrochemical approach resulting in a stable boron doping of titania nanotubes. The doping procedure concerns anodic polarization of as-anodized titania in a H₃BO₃ solution acting as n boron precursor. The series of attempts were taken in order to elaborate the most beneficial doping conditions. The parameters of electrochemical doping allowing to obtain boron-doped titania characterized by the highest photoconversion efficiency are as follows: reaction voltage 1.8 V, process duration 0.5 h, and the concentration of boric acid 0.5 M. Spectroscopy techniques such as UV-vis, X-ray diffraction, photoluminescence emission, and X-ray photoelectron spectroscopy were used to characterize the absorbance capability and the crystalline phase, to confirm the presence of boron atoms and to study the nature of chemical compounds, respectively. The well-ordered structure of titania and resistance of its morphology toward electrochemical treatment in H₃BO₃ were confirmed by scanning electron microscopy images. However, cyclic voltammetry and electrochemical impedance spectroscopy studies showed the significant difference in conductivity and capacitance between doped and pristine titania. Moreover, the photocurrent densities of the B-doped sample were about seven times higher in comparison with those generated by the pure titania nanotube electrode.

     

Acoustic deposition with NIMS as a high-throughput enzyme activity assay

Mass spectrometry (MS)-based enzyme assay has been shown to be a useful tool for screening enzymatic activities from environmental samples. Recently, reported approaches for high-specificity multiplexed characterization of enzymatic activities allow for providing detailed information on the range of enzymatic products and monitoring multiple enzymatic reactions. However, the throughput has been limited by the slow liquid-liquid handling and manual analysis. This rapid communication demonstrates the integration of acoustic sample deposition with nanostructure initiator mass spectrometry (NIMS) imaging to provide reproducible measurements of multiple enzymatic reactions at a throughput that is tenfold to 100-fold faster than conventional MS-based enzyme assay. It also provides a simple means for the visualization of multiple reactions and reaction pathways.     

Surlyn®/titanate hybrid materials via polymer in situ sol–gel chemistry

Acid form Surlyn®/titanate hybrid materials were achieved by polymer in situ sol–gel reactions for a titanium alkoxide monomer. Atomic force microscopic images revealed arrays of titania nanoparticles having diameters of 10–30 nm. Fourier transform infrared spectra verified the presence of an internally polymerized titanate phase although unhydrolyzed TiOR groups were present. Carboxylic acid dimerization was complete at room temperature, but carboxylate anions appeared at higher titanate levels. The methylene rocking doublet persisted upon incorporation of the inorganic component, which supported the idea of largely undisrupted crystallinity. Thermogravimetric analysis showed that the degradation onset temperature of each hybrid is largely unaffected by the presence of the inorganic filler, which is consistent with the concept of an isolated titanate phase. The first‐scan differential scanning calorimetric thermogram for unfilled Surlyn® revealed the usual twin‐melting endotherms. In contrast, the primary, high‐temperature melting endotherm was seen on the first scan for the Surlyn®/titanate hybrids, but the lower temperature endotherm was either not present or weak. Primary melting persisted after several cycles of heating above the melting temperature followed by cooling, demonstrating that primary crystallinity persisted despite titanate phase incorporation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 11–22, 2003