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721.
《国际聚合物材料杂志》2012,61(13):1106-1122
Novel polyhydroxyesterimides were prepared by the reaction between diglycidyl monomers and diimidodiacids at the molar ratio 1/1 in the presence of triethylbenzylamonim chloride as catalyst. Diimidodiacids (DIMDA) were obtained from Diels-Alder adduct of resin acids with maleic anhydride and two aromatic diamines, at the molar ratio 1:2. The chemical reactions between the diglycidyl monomers (diglycidylether of bisphenol A -DGEBA and diglycidyl ether of hydroquinone–DGEHQ) and diimidodiacids were monitored by using differential scanning calorimetry (DSC). The chemical structures of the obtained monomers and polymers were established by means of elemental analysis, FT-IR, 1H-NMR, and 13C-NMR methods. Thermal stability of the obtained polymers was also investigated and showed that they are reasonably thermostable. 相似文献
722.
《国际聚合物材料杂志》2012,61(13):1079-1090
Poly[tris((p-aminophenoxy)phosphineoxide)-3,3′,4,4′-benzophenonetetracarboxylicdiimide] (PAB) was used as an immobilized enzyme membrane for the fabrication of an amperometric glucose sensor. Enzyme immobilization was performed by two different methods and structural morphology of immobilized enzyme membrane was studied by SEM. The amperometric response of the sensor to hydrogen peroxide, formed as the product of the enzymatic reaction, was measured at a potential of 0.7 V in phosphate buffer solution by means of the TB technique. The influence of preparation conditions (polyimide film thickness, enzyme amount) on electrode performance was examined to obtain the optimal experimental parameters. Sensor characteristics (pH, response time, selectivity, stability) of the PAB/GOx/Pt electrode prepared under optimal conditions has been investigated. Results showed that this sensor exhibited a linear range up to 6 mM and a response time of about 60 s. with good stability. When glucose was injected into the PBS solution in the presence of fouling substances (lactose, sucrose, and urea), excellent amperometric responses were observed. Also, it was seen that the PAB/GOx-Pt electrode blocked the signal current of electroactive oxalic acid. 相似文献
723.
Nanocomposite films were prepared through the blending of polyimide (PI) with octaphenyl silsesquioxane (OPS) and an amino‐functionalized analogue, octaaminophenyl silsesquioxane (OAPS), with a solution‐casting method. Although the PI–OPS composites showed visible phase separation at 5 wt %, the PI–OAPS composites were transparent with visible phase separation occurring only at 50 wt % OAPS. The interfacial interactions and homogeneity of the composites were characterized with scanning electron microscopy (SEM) and dynamic mechanical analysis. SEM analysis showed a uniform fracture surface for OAPS composites at concentrations up to 20 wt %. Interestingly, OAPS‐rich particles with sizes of less than 1 μm were formed within the PI matrix for the 50 wt % composite. The PI–OAPS composites showed higher glass‐transition temperatures (Tg's) than the pure PI. The PI–OPS composites showed a Tg lower than that of the pure PI, and this suggested poor interfacial interactions. The slightly enhanced thermal stability of PI–OAPS composites (up to 20 wt %) was attributed to the inherent thermal stability of OAPS at higher temperatures. There were small increases in the modulus and strength for the composites with respect to the base polymer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
724.
Jingling Yan Zhen Wang Changli Lv Huili Yang Zhenping Shang Lianxun Gao Mengxian Ding 《应用聚合物科学杂志》2008,110(2):706-711
A novel, asymmetric diamine, 3‐(4‐aminophenylthio)‐N‐aminophthalimide, was prepared from 3‐chloro‐N‐aminophthalimide and 4‐aminobenzenethiol. The structure of the diamine was determined via IR and 1H‐NMR spectroscopy and elemental analysis. A series of polyimides were synthesized from 3‐(4‐aminophenylthio)‐N‐aminophthalimide and aromatic dianhydrides by a conventional two‐step method in N,N‐dimethylacetamide and by a one‐step method in phenols. These polyimides showed good solubility in 1‐methyl‐2‐pyrrolidinone, m‐cresol, and p‐chlorophenol, except polyimide from pyromellitic dianhydride, which was only soluble in p‐chlorophenol. The 5% weight loss temperatures of these polyimides ranged from 460 to 498°C in air. Dynamic mechanical thermal analysis indicated that the glass‐transition temperatures of the polyimides were in the range 278–395°C. The tensile strengths at break, moduli, and elongations of these polyimides were 146–178 MPa, 1.95–2.58 GPa, and 9.1–13.3%, respectively. Compared with corresponding polyimides from 4,4′‐diamiodiphenyl ether, these polymers showed enhanced solubility and higher glass‐transition temperatures. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
725.
A straightforward strategy is proposed to impart antimicrobial properties to biodegradable poly(oxepan-2-one) (poly(?-caprolactone) or PCL), which is based on the grafting of pendant ammonium salts by “click” chemistry. First, statistical copolymerization of 3-chlorooxepan-2-one (α-chloro-?-caprolactone or αCl?CL) with oxepan-2-one (?-caprolactone or ?CL) was initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP). In a second step, pendant chlorides were converted into azides by reaction with sodium azide (NaN3). Finally, quaternary ammonium containing alkynes were quantitatively added to the pendant azide groups of PCL by the copper-catalyzed Huisgen's 1,3-dipolar cycloaddition, which is a typical “click” reaction. An alternative two-step strategy based on the cycloaddition of the amine containing alkyne onto the pendant azides, followed by quaternization turned out to be less efficient. The antimicrobial activity was analyzed by the “shaking flask method” in the presence of Escherichia coli (E. coli). 相似文献
726.
We compared the chemical compositions of the osmeterial secretions of fourth and fifth (last) instars of eight swallowtail species of the tribe Papilionini. Four species (Papilio demoleus, P. polytes, P. paris, and P. macilentus) are Asian Rutaceae-feeding swallowtails. The other four (Chilasa epicydes, C. agestor, P. troilus, and P. glaucus) represent more distant clades within the Papilionini and species with larval hosts in other plant families. We conducted a quantitative analysis for six species, but only qualitative analysis for P. glaucus and C. agestor. In all eight species, regardless of larval host plant, secretions of the fourth instar principally consisted of mono- and sesquiterpene hydrocarbons, whereas those of the fifth instar comprised aliphatic acids and their esters. Consistent with earlier findings, our results suggest that this “heterogeneous” pattern of osmeterial chemistry, not seen in other tribes, may characterize the Papilionini as a whole. Unlike those of most Papilio species, the fourth and fifth instars of Chilasa species resemble each other in body coloration. Thus, the heterogeneous osmeterial pattern is not necessarily associated with color change in papilionid larvae. The major terpenoids identified in fourth instar larval secretions from the six species were α-pinene, sabinene, β-myrcene, limonene, β-phellandrene, (Z)-β-ocimene, (E)-β-ocimene, p-mentha-1,4(8)-diene, β-elemene, β-caryophyllene, (E)-β-farnesene, (3Z,6E)-α-farnesene, (Z)-α-bisabolene, germacrene-A, (E)-α-bisabolene, and germacrene-B. The profiles for individual species differed both qualitatively and quantitatively from one another, and certain species also secreted methyl 3-hydroxy-n-butyrate and oxygenated sesquiterpenes in relatively large proportions. Secretions from fifth instars were composed of varying proportions of isobutyric, 2-methylbutyric, and acetic acids, and methyl and ethyl (minor) esters of both isobutyric and 2-methylbutyric acids. The heterogeneity of osmeterial chemistry in the tribe Papilionini may represent fine-tuning of chemical defense in response to shifting predation pressures as the larvae age and grow. 相似文献
727.
Selectively enhanced oil retention of porous polyimide bearing materials by direct chemical modification 下载免费PDF全文
Porous polyimide (PI) materials containing lubricating oil have been widely used as bearing retainers in aerospace industry. High oil content and retention of porous bearing materials play an important role in assuring a successful mission of the spacecraft. Keeping both oil content and retention of bearing retainer materials high, however, is one of the bottlenecks to fulfill long lifetime missions. Chemical modification is expected to break this limitation by changing the surface properties. Inspired by this, here for the first time, the authors design a chemical method to improve silicon oil retention of porous PI samples. The results indicated that this modification could not only change the wettability of PI from hydrophilicity to hydrophobicity but also enhance the silicon oil retention from 52% to 87%. This strategy provides a novel approach to improve the oil retention of porous PI materials, which has the potential application in preparing bearing retainers with reliable, long‐term performance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45106. 相似文献
728.
The thermal rearrangement of polyimides of ortho-positioned functional group membranes improves the gas permselectivity properties of the polyimide precursor. For this experiment, HAB-6FDA polyimide was synthesized from 3,3 dihydroxy-4,4-diamino-biphenyl (HAB) and 2,2-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) by chemical imidization. A sample was modified from a pure polymer to silica nanoparticle composition. Furthermore, a modification was carried out by thermal rearrangement reaction at temperatures of 350, 400, and 450°C. The thermal property of these membrane films was characterized by differential scanning calorimetry (DSC), FTIR, opacity experiment, and free volume analysis. Permeability decreases with an increase in the kinetic diameter of gasses, which is normal behavior for glassy polymers. The composition of silica nanoparticles slightly changes the permeability in the polyimide. The combined effect of silica nanoparticles and thermal rearrangement of the HAB-6FDA membrane has shown an excellent performance. The thermal rearrangement with nanocomposite shows a significant impact on a larger effect on permeation for lighter gases, that is, H2, CO2, and O2, compared with N2 and CH4. Particularly for H2/CH4 gas pair, it lies over Robeson's 2008 upper bound limit, which fits the composition in the novel class for the gas separation membranes. 相似文献