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Polymerizable hexacatenar mesogens containing a photo-active oligo(p-phenylenevinylene) core were successfully synthesized by replacing the traditional n-alkoxy tails on the molecules with polymerizable hydrocarbon tails containing terminal isoprenyl or 1,3-dienyl units. It was found that for this particular liquid crystal (LC) platform, the incorporation of conventional radical polymerizable groups such as acrylates in the tails was not conducive to the formation of thermotropic LC phases, presumably due to their polar nature. The resulting photoluminescent isoprenyl and 1,3-dienyl hexacatenar monomers were found to form columnar hexagonal phases at elevated temperatures (c. 45–75°C), as determined by powder X-ray diffraction. Unfortunately, photoinitiated radical polymerization studies revealed that the mesogens are susceptible to photodegradation in the LC state at elevated temperatures, resulting in the loss of both LC order and emission properties during photopolymerization. Thermally initiated radical polymerization in the absence of light, however, afforded effective crosslinking with retention of both LC order and the desired emission properties. The resulting crosslinked columnar hexagonal phases were found to exhibit emission maxima at nearly identical wavelengths, with comparable intensities relative to the unpolymerized starting materials. The effect of the different polymerizable groups on the mesogenic behaviour, polymerization characteristics, and emission properties of the hexacatenar compounds is presented. 相似文献
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Yeong‐Tarng Shieh Gin‐Lung Liu Yawo‐Kuo Twu Tzong‐Liu Wang Chien‐Hsin Yang 《Journal of Polymer Science.Polymer Physics》2010,48(2):145-152
Effects of carbon nanotubes (CNT) on the dynamic mechanical property, thermal property, and crystal structure of poly(L ‐lactic acid) (PLLA) were investigated. Dynamic mechanical analysis (DMA) found that CNT via grafting modification with PLLA (CNT‐g‐PLLA) could result in effective reinforcing effects. Tan δ of DMA found that CNT‐g‐PLLA was compatible with the PLLA matrix, giving a single Tg of the composite with a higher CNT‐g‐PLLA loading giving a higher Tg of the composite. Wide angle X‐ray diffraction (WAXD) data demonstrated that CNT could assist the disorder‐to‐order (α′‐to‐α) transition in PLLA crystals but did not lead to a more compact chain packing of the crystal lattice in PLLA composites than in pure PLLA. The equilibrium melting temperature (T) obtained from Hoffman‐Weeks plots were found to increase with increasing CNT‐g‐PLLA content. Small angle X‐ray scattering data revealed that thicknesses of crystal layer and amorphous layer of PLLA both decreased with increasing CNT contents. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 145–152, 2010 相似文献
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High Ethene/Ethane Selectivity in 2,2′‐Bipyridine‐Based Silver(I) Complexes by Removal of Coordinated Solvent 下载免费PDF全文
Dr. Matthew G. Cowan William M. McDanel Prof. Hans H. Funke Dr. Yuki Kohno Prof. Douglas L. Gin Prof. Richard D. Noble 《Angewandte Chemie (International ed. in English)》2015,54(19):5740-5743
Following removal of coordinated CH3CN, the resulting complexes [AgI(2,2′‐bipyridine)][BF4] ( 1 ) and [AgI(6,6′‐dimethyl‐2,2′‐bipyridine)][OTf] ( 2 ) show ethene/ethane sorption selectivities of 390 and 340, respectively, and corresponding ethene sorption capacities of 2.38 and 2.18 mmol g?1 when tested at an applied gas pressure of 90 kPa and a temperature of (20±1) °C. These ethene/ethane selectivities are 13 times higher than those reported for known solid sorbents for ethene/ethane separation. For 2 , ethene sorption reached 90 % of equilibrium capacity within 15 minutes, and this equilibrium capacity was maintained over the three sorption/desorption cycles tested. The rates of ethene sorption were also measured. To our knowledge, these are the first complexes, designed for olefin/paraffin separations, which have open silver(I) sites. The high selectivities arise from these open silver(I) sites and the relatively low molecular surface areas of the complexes. 相似文献
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In flow injection analysis, several plugs can be injected simultaneously into the same carrier system, in order to achieve overlapped zones. The potentialities of such sequential injections are studied in model systems with spectrophotometric detection; the procedure is shown to give better precision than the use of concentration gradients. The method is used with atomic absorption spectrometry to allow the determination of a wide range of manganese contents in rocks, and to facilitate the use of standard additions for the determination of copper in ethanol. 相似文献
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Patrick Jollivet Frédéric Angeli Céline Cailleteau François Devreux P. Frugier S. Gin 《Journal of Non》2008,354(45-46):4952-4958
A 5-oxide glass (62.5SiO2, 16.6B2O3, 13.1Na2O, 6.0CaO, 1.8ZrO2) was leached at 90 °C at a high glass-surface-area-to-solution-volume ratio (SA/V = 80 cm?1). Its dissolution rate diminished over time until it became unmeasurable. The alteration layer was characterized by 29Si isotopic tracing in the leaching solution. ToF-SIMS elemental profiles showed that glass dissolution ceased due to clogging of the gel porosity at the gel/solution interface. One of the hypotheses proposed to account for the rate drop observed during borosilicate glass alteration is based on morphological changes in the alteration gel over time. Monte Carlo modeling of glass alteration, especially with simple glasses, indicates a clogging of the porosity on the external portion of the gel (near the solution/gel interface) after densification of the layer by silicon precipitation, but this phenomenon had never previously been directly observed experimentally. The initial results obtained by isotopic tracing provide new data that appears to confirm this hypothesis. 相似文献