排序方式: 共有33条查询结果,搜索用时 31 毫秒
1.
Paula C. Rodrigues Bruno D. Fontes Bruno B. M. Torres Washington S. Sousa Gregório C. Faria Debora T. Balogh Roberto M. Faria Leni Akcelrud 《应用聚合物科学杂志》2015,132(38)
Synthesis of a polyfluorene/poly(p‐phenylene vinylene) derivative, the Poly [(9,9′‐di‐hexylfluorenediylvinylene‐alt‐1,4‐phenylenevinylene)‐co‐((9,9′‐(3‐t‐butylpropanoate) fluorene‐1,4‐phenylene)] (LaPPS 42) was performed following Wittig and Suzuki routes. Polyfluorenes and derivatives have been used in electroluminescent devices, and the synthesis described here has the advantage in pave the way to get distinct structures having different emission spectra. An extensive study of its electrochemical, thermomechanical, optical, and structural properties was carried out, as well as its application in electroluminescent devices. Polymer light‐emitting diodes (PLEDs) and polymer light‐emitting electrochemical cells (PLECs) were built using LaPPS 42 as active layer, and their electric and optical characterizations confirm they have a potential as active element in electroluminescent devices. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42579. 相似文献
2.
Some ideas relevant to the prevailing viscoelasticity interpretations of dynamic mechanical thermal analysis (DMTA) experiments
are presented. The main aspect is the inclusion of kinetic energy and inertia as variables, seeing the relaxing mass constantly
increasing during strain, assigning inertial variation and not viscosity to energy dissipation. The equations developed make
it possible to obtain the values of important viscoelastic properties, under in any experimental condition, with the data
taken from previous experiments. 相似文献
3.
Crosslinked polyethylene (XLPE) is progressively replacing other types of polyethylene in electric cable insulation because of its combination of better mechanical and thermal performance and good dielectric properties. Besides its influence on the mechanical and thermal properties, the morphology plays a very important role in the electrical behavior of XLPE. The morphology has been studied in terms of the crystallinity and crosslinking density. These two apparently independent parameters govern the morphology of XLPE and have been investigated in connection with the systematic variation of the processing parameters (crosslinker concentration, cure time, and temperature). The materials have been characterized in terms of the extent of crosslinking (the gel content), the crosslinking density (the average molecular weight between crosslinks), and the crystallinity. A morphological model is proposed for these materials in terms of the mechanisms and rates of the processes involved. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 222–230, 2004 相似文献
4.
Characterization of hydroxyl-terminated polybutadiene 总被引:1,自引:0,他引:1
Commercial samples of hydroxyl terminated polybutadienes (HTPB) were analysed by 1H and 13C NMR spectroscopy, in regard to hydroxylated end groups. The results were discussed and compared with those reported so far. 相似文献
5.
Oligobutadiene-based prepolymers and polyurethanes (PU) were prepared from hydroxyl terminated polybutadiene (HTPB), three diisocyanates (aromatic, alicyclic and aliphatic) and two chain extenders (containing hydroxyl or amino groups). The free NCO content in the prepolymers varied systematically and the characteristic of these products were interpreted in terms of NCO group reactivity, propagation reactions and HTPB functionality. The mechanical properties of the polyurethane elastomers derived from the prepolymers were discussed in terms of hard and soft segment structures. 相似文献
6.
Edith Leclercq Alphons G. J. Voragen Leni M. Brugging Walter Pilnik 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1988,187(5):440-443
Summary The solubility of lactucin, 8-deoxylactucin and lactucopicrin, all sesquiterpene lactones of chicory roots, was determined as a function of pH (pH 1–10) in the presence and absence of polysaccharides. The stability of the sesquiterpene lactones, when dissolved in water, decreased under influence of daylight as a function of pH. Enzymatic hydrolysis of lactucopicrin by commercial enzyme preparations, used for liquefaction of chicory roots into lactucin and p-hydroxyphenylacetic acid, was not found.
Einfluß von Licht, Lösungsmittel und Handelsenzymen auf die Löslichkeit und Stabilität der Sesquiterpen-Lactone von Zichorienwurzeln
Zusammenfassung Die Stabilität von LaCA Bussurnctucin, 8-Deoxylactucin und Lactucopicrin (alles SesquiterpenLactone der Zichorienwurzel) wurde in Abhängigkeit vom pH-Wert beim Aufbewahren im Licht studiert. Es konnte ein Abbau dieser Verbindungen nachgewiesen werden. Die Löslichkeit dieser drei Verbindungen wurde in Abhängigkeit vom pH-Wert mit und ohne Polysaccharide bestimmt. Es wurde keine Hydrolyse des Lactucopicrins unter der Einwirkung von kommerziellen Enzymen, die bei der Verflüssigung von Zichorienwurzeln verwendet werden, gefunden.相似文献
7.
8.
K.A.S. Araujo P.S.S. Guimarães L.A. Cury L. Akcelrud D. Sanvitto M. De Giorgi M. Valadares H.D.R. Calado 《Organic Electronics》2012,13(12):2843-2849
Optical properties of poly(n-vinylcarbazole) (PVK) thin films are revisited. Steady-state emission spectra put in evidence a strong red band whose intensity increases with decreasing temperature when the solid state PVK film is excited by a continuous 375 nm laser line. This red band is assigned to the emission from PVK aggregate states which act as trap states for the monomeric PVK triplet high energy (blue) excitons. At the same low temperatures, these trap states can be avoided when the excitation of the PVK film is made by a 355 nm pulsed laser line with 10 Hz repetition rate. The red band was also observed to compete with the emission of guest poly(3-octadecylthiophene) (PODT) molecules in a PVK/PODT sequential bilayer structure. Different optical geometries enabled us to show that the exciton energy transfer effect from PVK donor to PODT acceptor states dominates the scenario in the bilayer structure, suppressing almost completely the trap state emissions. 相似文献
9.
S. F. Zawadzki D. Tabak L. Akcelrud 《Polymer-Plastics Technology and Engineering》2013,52(1-2):155-165
The compatibility of PVC with poly(diethylene glycol adipate) M n = 1500 was evaluated by DSC, indicating a limit value of 15 phr. The behavior of the oligomer as a PVC plasticizer, alone or in combination with dioctylphthalate (DOP), was investigated by measurements such as hardness, glass transition temperature, heat stability, and solvent resistance. In spite of its limited compatibility the oligoester can act as a secondary plasticizer enhancing the overall performance of the compositions. 相似文献
10.
Rafael F. Cossiello Ali Cirpan Frank E. Karasz Leni Akcelrud Teresa D.Z. Atvars 《Synthetic Metals》2008,158(6):219-225
This work reports the electroluminescence of poly[2-methoxy-5(2′-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) and poly(styrene-co-acrylic acid-co-1-pyrenylmethyl methacrylate) (SAA) blends in ratios from 0 to 100 wt.% in mass of MEH-PPV. The styrene-co-acrylic copolymer was synthesized with 3 mol% of acrylic acid units to simultaneously enhance blend miscibility and charge transport in MEH-PPV. The morphology was studied using epifluorescence microscopy and scanning electron microscopy in which the pyrenyl-labeled copolymer is used to enhance microscopic contrast. Device performances were compared: those using MEH-PPV have a turn-on voltage of 3.5 V, luminance of 500 cd/m2 and current density of 430 mA/cm2 at 5 V, while MEH-PPV blended with 50 wt.% styrene–acrylic copolymer showed a turn-on voltage of 2.5 V, a luminance of 2300 cd/A and a current density of 640 mA/cm2 at 5 V. 相似文献